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https://codeberg.org/redict/redict.git
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d4e7ffb38c
Background: Following the upgrade to jemalloc 5.2, there was a test that used to be flaky and started failing consistently (on 32bit), so we disabled it (see #9645). This is a test that i introduced in #7289 when i attempted to solve a rare stagnation problem, and it later turned out i failed to solve it, ans what's more i added a test that caused it to be not so rare, and as i mentioned, now in jemalloc 5.2 it became consistent on 32bit. Stagnation can happen when all the slabs of the bin are equally utilized, so the decision to move an allocation from a relatively empty slab to a relatively full one, will never happen, and in that test all the slabs are at 50% utilization, so the defragger could just keep scanning the keyspace and not move anything. What this PR changes: * First, finally in jemalloc 5.2 we have the count of non-full slabs, so when we compare the utilization of the current slab, we can compare it to the average utilization of the non-full slabs in our bin, instead of the total average of our bin. this takes the full slabs out of the game, since they're not candidates for migration (neither source nor target). * Secondly, We add some 12% (100/8) to the decision to defrag an allocation, this is the part that aims to avoid stagnation, and it's especially important since the above mentioned change can get us closer to stagnation. * Thirdly, since jemalloc 5.2 adds sharded bins, we take into account all shards (something that's missing from the original PR that merged it), this isn't expected to make any difference since anyway there should be just one shard. How this was benchmarked. What i did was run the memefficiency test unit with `--verbose` and compare the defragger hits and misses the tests reported. At first, when i took into consideration only the non-full slabs, it got a lot worse (i got into stagnation, or just got a lot of misses and a lot of hits), but when i added the 10% i got back to results that were slightly better than the ones of the jemalloc 5.1 branch. i.e. full defragmentation was achieved with fewer hits (relocations), and fewer misses (keyspace scans).
497 lines
21 KiB
Tcl
497 lines
21 KiB
Tcl
proc test_memory_efficiency {range} {
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r flushall
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set rd [redis_deferring_client]
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set base_mem [s used_memory]
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set written 0
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for {set j 0} {$j < 10000} {incr j} {
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set key key:$j
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set val [string repeat A [expr {int(rand()*$range)}]]
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$rd set $key $val
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incr written [string length $key]
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incr written [string length $val]
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incr written 2 ;# A separator is the minimum to store key-value data.
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}
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for {set j 0} {$j < 10000} {incr j} {
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$rd read ; # Discard replies
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}
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set current_mem [s used_memory]
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set used [expr {$current_mem-$base_mem}]
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set efficiency [expr {double($written)/$used}]
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return $efficiency
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}
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start_server {tags {"memefficiency external:skip"}} {
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foreach {size_range expected_min_efficiency} {
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32 0.15
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64 0.25
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128 0.35
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1024 0.75
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16384 0.82
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} {
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test "Memory efficiency with values in range $size_range" {
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set efficiency [test_memory_efficiency $size_range]
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assert {$efficiency >= $expected_min_efficiency}
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}
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}
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}
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run_solo {defrag} {
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start_server {tags {"defrag external:skip"} overrides {appendonly yes auto-aof-rewrite-percentage 0 save ""}} {
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if {[string match {*jemalloc*} [s mem_allocator]] && [r debug mallctl arenas.page] <= 8192} {
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test "Active defrag" {
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r config set hz 100
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r config set activedefrag no
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r config set active-defrag-threshold-lower 5
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r config set active-defrag-cycle-min 65
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r config set active-defrag-cycle-max 75
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r config set active-defrag-ignore-bytes 2mb
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r config set maxmemory 100mb
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r config set maxmemory-policy allkeys-lru
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populate 700000 asdf1 150
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populate 170000 asdf2 300
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after 120 ;# serverCron only updates the info once in 100ms
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set frag [s allocator_frag_ratio]
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if {$::verbose} {
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puts "frag $frag"
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}
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assert {$frag >= 1.4}
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r config set latency-monitor-threshold 5
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r latency reset
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r config set maxmemory 110mb ;# prevent further eviction (not to fail the digest test)
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set digest [r debug digest]
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catch {r config set activedefrag yes} e
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if {[r config get activedefrag] eq "activedefrag yes"} {
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# Wait for the active defrag to start working (decision once a
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# second).
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wait_for_condition 50 100 {
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[s active_defrag_running] ne 0
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} else {
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fail "defrag not started."
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}
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# Wait for the active defrag to stop working.
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wait_for_condition 2000 100 {
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[s active_defrag_running] eq 0
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} else {
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after 120 ;# serverCron only updates the info once in 100ms
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puts [r info memory]
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puts [r memory malloc-stats]
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fail "defrag didn't stop."
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}
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# Test the the fragmentation is lower.
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after 120 ;# serverCron only updates the info once in 100ms
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set frag [s allocator_frag_ratio]
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set max_latency 0
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foreach event [r latency latest] {
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lassign $event eventname time latency max
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if {$eventname == "active-defrag-cycle"} {
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set max_latency $max
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}
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}
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if {$::verbose} {
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puts "frag $frag"
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set misses [s active_defrag_misses]
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set hits [s active_defrag_hits]
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puts "hits: $hits"
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puts "misses: $misses"
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puts "max latency $max_latency"
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puts [r latency latest]
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puts [r latency history active-defrag-cycle]
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}
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assert {$frag < 1.1}
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# due to high fragmentation, 100hz, and active-defrag-cycle-max set to 75,
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# we expect max latency to be not much higher than 7.5ms but due to rare slowness threshold is set higher
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if {!$::no_latency} {
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assert {$max_latency <= 30}
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}
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}
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# verify the data isn't corrupted or changed
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set newdigest [r debug digest]
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assert {$digest eq $newdigest}
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r save ;# saving an rdb iterates over all the data / pointers
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# if defrag is supported, test AOF loading too
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if {[r config get activedefrag] eq "activedefrag yes"} {
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# reset stats and load the AOF file
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r config resetstat
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r config set key-load-delay -50 ;# sleep on average 1/50 usec
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r debug loadaof
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r config set activedefrag no
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# measure hits and misses right after aof loading
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set misses [s active_defrag_misses]
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set hits [s active_defrag_hits]
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after 120 ;# serverCron only updates the info once in 100ms
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set frag [s allocator_frag_ratio]
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set max_latency 0
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foreach event [r latency latest] {
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lassign $event eventname time latency max
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if {$eventname == "while-blocked-cron"} {
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set max_latency $max
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}
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}
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if {$::verbose} {
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puts "AOF loading:"
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puts "frag $frag"
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puts "hits: $hits"
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puts "misses: $misses"
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puts "max latency $max_latency"
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puts [r latency latest]
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puts [r latency history "while-blocked-cron"]
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}
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# make sure we had defrag hits during AOF loading
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assert {$hits > 100000}
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# make sure the defragger did enough work to keep the fragmentation low during loading.
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# we cannot check that it went all the way down, since we don't wait for full defrag cycle to complete.
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assert {$frag < 1.4}
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# since the AOF contains simple (fast) SET commands (and the cron during loading runs every 1000 commands),
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# it'll still not block the loading for long periods of time.
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if {!$::no_latency} {
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assert {$max_latency <= 30}
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}
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}
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}
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r config set appendonly no
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r config set key-load-delay 0
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test "Active defrag big keys" {
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r flushdb
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r config resetstat
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r config set hz 100
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r config set activedefrag no
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r config set active-defrag-max-scan-fields 1000
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r config set active-defrag-threshold-lower 5
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r config set active-defrag-cycle-min 65
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r config set active-defrag-cycle-max 75
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r config set active-defrag-ignore-bytes 2mb
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r config set maxmemory 0
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r config set list-max-ziplist-size 5 ;# list of 10k items will have 2000 quicklist nodes
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r config set stream-node-max-entries 5
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r hmset hash h1 v1 h2 v2 h3 v3
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r lpush list a b c d
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r zadd zset 0 a 1 b 2 c 3 d
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r sadd set a b c d
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r xadd stream * item 1 value a
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r xadd stream * item 2 value b
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r xgroup create stream mygroup 0
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r xreadgroup GROUP mygroup Alice COUNT 1 STREAMS stream >
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# create big keys with 10k items
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set rd [redis_deferring_client]
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for {set j 0} {$j < 10000} {incr j} {
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$rd hset bighash $j [concat "asdfasdfasdf" $j]
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$rd lpush biglist [concat "asdfasdfasdf" $j]
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$rd zadd bigzset $j [concat "asdfasdfasdf" $j]
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$rd sadd bigset [concat "asdfasdfasdf" $j]
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$rd xadd bigstream * item 1 value a
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}
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for {set j 0} {$j < 50000} {incr j} {
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$rd read ; # Discard replies
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}
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set expected_frag 1.7
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if {$::accurate} {
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# scale the hash to 1m fields in order to have a measurable the latency
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for {set j 10000} {$j < 1000000} {incr j} {
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$rd hset bighash $j [concat "asdfasdfasdf" $j]
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}
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for {set j 10000} {$j < 1000000} {incr j} {
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$rd read ; # Discard replies
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}
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# creating that big hash, increased used_memory, so the relative frag goes down
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set expected_frag 1.3
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}
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# add a mass of string keys
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for {set j 0} {$j < 500000} {incr j} {
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$rd setrange $j 150 a
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}
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for {set j 0} {$j < 500000} {incr j} {
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$rd read ; # Discard replies
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}
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assert_equal [r dbsize] 500010
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# create some fragmentation
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for {set j 0} {$j < 500000} {incr j 2} {
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$rd del $j
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}
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for {set j 0} {$j < 500000} {incr j 2} {
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$rd read ; # Discard replies
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}
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assert_equal [r dbsize] 250010
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# start defrag
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after 120 ;# serverCron only updates the info once in 100ms
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set frag [s allocator_frag_ratio]
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if {$::verbose} {
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puts "frag $frag"
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}
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assert {$frag >= $expected_frag}
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r config set latency-monitor-threshold 5
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r latency reset
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set digest [r debug digest]
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catch {r config set activedefrag yes} e
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if {[r config get activedefrag] eq "activedefrag yes"} {
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# wait for the active defrag to start working (decision once a second)
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wait_for_condition 50 100 {
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[s active_defrag_running] ne 0
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} else {
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fail "defrag not started."
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}
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# wait for the active defrag to stop working
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wait_for_condition 500 100 {
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[s active_defrag_running] eq 0
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} else {
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after 120 ;# serverCron only updates the info once in 100ms
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puts [r info memory]
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puts [r memory malloc-stats]
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fail "defrag didn't stop."
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}
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# test the the fragmentation is lower
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after 120 ;# serverCron only updates the info once in 100ms
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set frag [s allocator_frag_ratio]
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set max_latency 0
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foreach event [r latency latest] {
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lassign $event eventname time latency max
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if {$eventname == "active-defrag-cycle"} {
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set max_latency $max
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}
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}
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if {$::verbose} {
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puts "frag $frag"
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set misses [s active_defrag_misses]
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set hits [s active_defrag_hits]
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puts "hits: $hits"
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puts "misses: $misses"
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puts "max latency $max_latency"
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puts [r latency latest]
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puts [r latency history active-defrag-cycle]
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}
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assert {$frag < 1.1}
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# due to high fragmentation, 100hz, and active-defrag-cycle-max set to 75,
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# we expect max latency to be not much higher than 7.5ms but due to rare slowness threshold is set higher
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if {!$::no_latency} {
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assert {$max_latency <= 30}
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}
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}
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# verify the data isn't corrupted or changed
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set newdigest [r debug digest]
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assert {$digest eq $newdigest}
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r save ;# saving an rdb iterates over all the data / pointers
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} {OK}
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test "Active defrag big list" {
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r flushdb
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r config resetstat
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r config set hz 100
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r config set activedefrag no
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r config set active-defrag-max-scan-fields 1000
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r config set active-defrag-threshold-lower 5
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r config set active-defrag-cycle-min 65
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r config set active-defrag-cycle-max 75
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r config set active-defrag-ignore-bytes 2mb
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r config set maxmemory 0
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r config set list-max-ziplist-size 5 ;# list of 500k items will have 100k quicklist nodes
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# create big keys with 10k items
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set rd [redis_deferring_client]
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set expected_frag 1.7
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# add a mass of list nodes to two lists (allocations are interlaced)
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set val [string repeat A 100] ;# 5 items of 100 bytes puts us in the 640 bytes bin, which has 32 regs, so high potential for fragmentation
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set elements 500000
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for {set j 0} {$j < $elements} {incr j} {
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$rd lpush biglist1 $val
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$rd lpush biglist2 $val
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}
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for {set j 0} {$j < $elements} {incr j} {
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$rd read ; # Discard replies
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$rd read ; # Discard replies
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}
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# create some fragmentation
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r del biglist2
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# start defrag
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after 120 ;# serverCron only updates the info once in 100ms
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set frag [s allocator_frag_ratio]
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if {$::verbose} {
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puts "frag $frag"
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}
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assert {$frag >= $expected_frag}
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r config set latency-monitor-threshold 5
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r latency reset
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set digest [r debug digest]
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catch {r config set activedefrag yes} e
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if {[r config get activedefrag] eq "activedefrag yes"} {
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# wait for the active defrag to start working (decision once a second)
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wait_for_condition 50 100 {
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[s active_defrag_running] ne 0
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} else {
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fail "defrag not started."
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}
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# wait for the active defrag to stop working
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wait_for_condition 500 100 {
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[s active_defrag_running] eq 0
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} else {
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after 120 ;# serverCron only updates the info once in 100ms
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puts [r info memory]
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puts [r info stats]
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puts [r memory malloc-stats]
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fail "defrag didn't stop."
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}
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# test the the fragmentation is lower
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after 120 ;# serverCron only updates the info once in 100ms
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set misses [s active_defrag_misses]
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set hits [s active_defrag_hits]
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set frag [s allocator_frag_ratio]
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set max_latency 0
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foreach event [r latency latest] {
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lassign $event eventname time latency max
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if {$eventname == "active-defrag-cycle"} {
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set max_latency $max
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}
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}
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if {$::verbose} {
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puts "frag $frag"
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puts "misses: $misses"
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puts "hits: $hits"
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puts "max latency $max_latency"
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puts [r latency latest]
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puts [r latency history active-defrag-cycle]
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}
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assert {$frag < 1.1}
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# due to high fragmentation, 100hz, and active-defrag-cycle-max set to 75,
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# we expect max latency to be not much higher than 7.5ms but due to rare slowness threshold is set higher
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if {!$::no_latency} {
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assert {$max_latency <= 30}
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}
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# in extreme cases of stagnation, we see over 20m misses before the tests aborts with "defrag didn't stop",
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# in normal cases we only see 100k misses out of 500k elements
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assert {$misses < $elements}
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}
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# verify the data isn't corrupted or changed
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set newdigest [r debug digest]
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assert {$digest eq $newdigest}
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r save ;# saving an rdb iterates over all the data / pointers
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r del biglist1 ;# coverage for quicklistBookmarksClear
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} {1}
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test "Active defrag edge case" {
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# there was an edge case in defrag where all the slabs of a certain bin are exact the same
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# % utilization, with the exception of the current slab from which new allocations are made
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# if the current slab is lower in utilization the defragger would have ended up in stagnation,
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# kept running and not move any allocation.
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# this test is more consistent on a fresh server with no history
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start_server {tags {"defrag"} overrides {save ""}} {
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r flushdb
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r config resetstat
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r config set hz 100
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r config set activedefrag no
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r config set active-defrag-max-scan-fields 1000
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r config set active-defrag-threshold-lower 5
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r config set active-defrag-cycle-min 65
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r config set active-defrag-cycle-max 75
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r config set active-defrag-ignore-bytes 1mb
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r config set maxmemory 0
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set expected_frag 1.3
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r debug mallctl-str thread.tcache.flush VOID
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# fill the first slab containin 32 regs of 640 bytes.
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for {set j 0} {$j < 32} {incr j} {
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r setrange "_$j" 600 x
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r debug mallctl-str thread.tcache.flush VOID
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}
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# add a mass of keys with 600 bytes values, fill the bin of 640 bytes which has 32 regs per slab.
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set rd [redis_deferring_client]
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set keys 640000
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for {set j 0} {$j < $keys} {incr j} {
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$rd setrange $j 600 x
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}
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for {set j 0} {$j < $keys} {incr j} {
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$rd read ; # Discard replies
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}
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# create some fragmentation of 50%
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set sent 0
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for {set j 0} {$j < $keys} {incr j 1} {
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$rd del $j
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incr sent
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incr j 1
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}
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for {set j 0} {$j < $sent} {incr j} {
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$rd read ; # Discard replies
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}
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# create higher fragmentation in the first slab
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for {set j 10} {$j < 32} {incr j} {
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r del "_$j"
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}
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# start defrag
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after 120 ;# serverCron only updates the info once in 100ms
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set frag [s allocator_frag_ratio]
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if {$::verbose} {
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puts "frag $frag"
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}
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assert {$frag >= $expected_frag}
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set digest [r debug digest]
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catch {r config set activedefrag yes} e
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if {[r config get activedefrag] eq "activedefrag yes"} {
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# wait for the active defrag to start working (decision once a second)
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wait_for_condition 50 100 {
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[s active_defrag_running] ne 0
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} else {
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fail "defrag not started."
|
|
}
|
|
|
|
# wait for the active defrag to stop working
|
|
wait_for_condition 500 100 {
|
|
[s active_defrag_running] eq 0
|
|
} else {
|
|
after 120 ;# serverCron only updates the info once in 100ms
|
|
puts [r info memory]
|
|
puts [r info stats]
|
|
puts [r memory malloc-stats]
|
|
fail "defrag didn't stop."
|
|
}
|
|
|
|
# test the the fragmentation is lower
|
|
after 120 ;# serverCron only updates the info once in 100ms
|
|
set misses [s active_defrag_misses]
|
|
set hits [s active_defrag_hits]
|
|
set frag [s allocator_frag_ratio]
|
|
if {$::verbose} {
|
|
puts "frag $frag"
|
|
puts "hits: $hits"
|
|
puts "misses: $misses"
|
|
}
|
|
assert {$frag < 1.1}
|
|
assert {$misses < 10000000} ;# when defrag doesn't stop, we have some 30m misses, when it does, we have 2m misses
|
|
}
|
|
|
|
# verify the data isn't corrupted or changed
|
|
set newdigest [r debug digest]
|
|
assert {$digest eq $newdigest}
|
|
r save ;# saving an rdb iterates over all the data / pointers
|
|
}
|
|
}
|
|
}
|
|
}
|
|
} ;# run_solo
|