caleb-brown/redict
1
0
Fork 0
mirror of https://codeberg.org/redict/redict.git synced 2025-01-23 00:28:26 -05:00
Code Issues Actions Packages Projects Releases Wiki Activity

Merge pull request #7289 from oranagra/defrag_edge_case

Browse Source 
fix a rare active defrag edge case bug leading to stagnation
This commit is contained in:
Salvatore Sanfilippo 2020-05-20 15:17:02 +02:00 committed by GitHub
commit af34245692
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 173 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
deps/jemalloc/include/jemalloc/internal/jemalloc_internal_inlines_c.h vendored
View File

@ -216,7 +216,7 @@ ixalloc(tsdn_t *tsdn, void *ptr, size_t oldsize, size_t size, size_t extra,
}
JEMALLOC_ALWAYS_INLINE int
iget_defrag_hint(tsdn_t *tsdn, void* ptr, int *bin_util, int *run_util) {
iget_defrag_hint(tsdn_t *tsdn, void* ptr) {
int defrag = 0;
rtree_ctx_t rtree_ctx_fallback;
rtree_ctx_t *rtree_ctx = tsdn_rtree_ctx(tsdn, &rtree_ctx_fallback);
@ -232,11 +232,22 @@ iget_defrag_hint(tsdn_t *tsdn, void* ptr, int *bin_util, int *run_util) {
malloc_mutex_lock(tsdn, &bin->lock);
/* don't bother moving allocations from the slab currently used for new allocations */
if (slab != bin->slabcur) {
const bin_info_t *bin_info = &bin_infos[binind];
size_t availregs = bin_info->nregs * bin->stats.curslabs;
*bin_util = ((long long)bin->stats.curregs<<16) / availregs;
*run_util = ((long long)(bin_info->nregs - extent_nfree_get(slab))<<16) / bin_info->nregs;
defrag = 1;
int free_in_slab = extent_nfree_get(slab);
if (free_in_slab) {
const bin_info_t *bin_info = &bin_infos[binind];
int curslabs = bin->stats.curslabs;
size_t curregs = bin->stats.curregs;
if (bin->slabcur) {
/* remove slabcur from the overall utilization */
curregs -= bin_info->nregs - extent_nfree_get(bin->slabcur);
curslabs -= 1;
}
/* Compare the utilization ratio of the slab in question to the total average,
* to avoid precision lost and division, we do that by extrapolating the usage
* of the slab as if all slabs have the same usage. If this slab is less used
* than the average, we'll prefer to evict the data to hopefully more used ones */
defrag = (bin_info->nregs - free_in_slab) * curslabs <= curregs;
}
}
malloc_mutex_unlock(tsdn, &bin->lock);
}

8
deps/jemalloc/src/jemalloc.c vendored
View File

@ -3326,12 +3326,10 @@ jemalloc_postfork_child(void) {
/******************************************************************************/
/* Helps the application decide if a pointer is worth re-allocating in order to reduce fragmentation.
* returns 0 if the allocation is in the currently active run,
* or when it is not causing any frag issue (large or huge bin)
* returns the bin utilization and run utilization both in fixed point 16:16.
* returns 1 if the allocation should be moved, and 0 if the allocation be kept.
* If the application decides to re-allocate it should use MALLOCX_TCACHE_NONE when doing so. */
JEMALLOC_EXPORT int JEMALLOC_NOTHROW
get_defrag_hint(void* ptr, int *bin_util, int *run_util) {
get_defrag_hint(void* ptr) {
assert(ptr != NULL);
return iget_defrag_hint(TSDN_NULL, ptr, bin_util, run_util);
return iget_defrag_hint(TSDN_NULL, ptr);
}

34
src/debug.c
View File

@ -311,6 +311,13 @@ void mallctl_int(client *c, robj **argv, int argc) {
size_t sz = sizeof(old);
while (sz > 0) {
if ((ret=je_mallctl(argv[0]->ptr, &old, &sz, argc > 1? &val: NULL, argc > 1?sz: 0))) {
if (ret == EPERM && argc > 1) {
/* if this option is write only, try just writing to it. */
if (!(ret=je_mallctl(argv[0]->ptr, NULL, 0, &val, sz))) {
addReply(c, shared.ok);
return;
}
}
if (ret==EINVAL) {
/* size might be wrong, try a smaller one */
sz /= 2;
@ -333,17 +340,30 @@ void mallctl_int(client *c, robj **argv, int argc) {
}
void mallctl_string(client *c, robj **argv, int argc) {
int ret;
int rret, wret;
char *old;
size_t sz = sizeof(old);
/* for strings, it seems we need to first get the old value, before overriding it. */
if ((ret=je_mallctl(argv[0]->ptr, &old, &sz, NULL, 0))) {
addReplyErrorFormat(c,"%s", strerror(ret));
return;
if ((rret=je_mallctl(argv[0]->ptr, &old, &sz, NULL, 0))) {
/* return error unless this option is write only. */
if (!(rret == EPERM && argc > 1)) {
addReplyErrorFormat(c,"%s", strerror(rret));
return;
}
}
addReplyBulkCString(c, old);
if(argc > 1)
je_mallctl(argv[0]->ptr, NULL, 0, &argv[1]->ptr, sizeof(char*));
if(argc > 1) {
char *val = argv[1]->ptr;
char **valref = &val;
if ((!strcmp(val,"VOID")))
valref = NULL, sz = 0;
wret = je_mallctl(argv[0]->ptr, NULL, 0, valref, sz);
}
if (!rret)
addReplyBulkCString(c, old);
else if (wret)
addReplyErrorFormat(c,"%s", strerror(wret));
else
addReply(c, shared.ok);
}
#endif

13
src/defrag.c
View File

@ -43,7 +43,7 @@
/* this method was added to jemalloc in order to help us understand which
* pointers are worthwhile moving and which aren't */
int je_get_defrag_hint(void* ptr, int *bin_util, int *run_util);
int je_get_defrag_hint(void* ptr);
/* forward declarations*/
void defragDictBucketCallback(void *privdata, dictEntry **bucketref);
@ -55,18 +55,11 @@ dictEntry* replaceSateliteDictKeyPtrAndOrDefragDictEntry(dict *d, sds oldkey, sd
* when it returns a non-null value, the old pointer was already released
* and should NOT be accessed. */
void* activeDefragAlloc(void *ptr) {
int bin_util, run_util;
size_t size;
void *newptr;
if(!je_get_defrag_hint(ptr, &bin_util, &run_util)) {
server.stat_active_defrag_misses++;
return NULL;
}
/* if this run is more utilized than the average utilization in this bin
* (or it is full), skip it. This will eventually move all the allocations
* from relatively empty runs into relatively full runs. */
if (run_util > bin_util || run_util == 1<<16) {
if(!je_get_defrag_hint(ptr)) {
server.stat_active_defrag_misses++;
size = zmalloc_size(ptr);
return NULL;
}
/* move this allocation to a new allocation.

125
tests/unit/memefficiency.tcl
View File

@ -95,6 +95,10 @@ start_server {tags {"defrag"}} {
}
if {$::verbose} {
puts "frag $frag"
set misses [s active_defrag_misses]
set hits [s active_defrag_hits]
puts "hits: $hits"
puts "misses: $misses"
puts "max latency $max_latency"
puts [r latency latest]
puts [r latency history active-defrag-cycle]
@ -221,6 +225,10 @@ start_server {tags {"defrag"}} {
}
if {$::verbose} {
puts "frag $frag"
set misses [s active_defrag_misses]
set hits [s active_defrag_hits]
puts "hits: $hits"
puts "misses: $misses"
puts "max latency $max_latency"
puts [r latency latest]
puts [r latency history active-defrag-cycle]
@ -256,11 +264,12 @@ start_server {tags {"defrag"}} {
set expected_frag 1.7
# add a mass of list nodes to two lists (allocations are interlaced)
set val [string repeat A 100] ;# 5 items of 100 bytes puts us in the 640 bytes bin, which has 32 regs, so high potential for fragmentation
for {set j 0} {$j < 500000} {incr j} {
set elements 500000
for {set j 0} {$j < $elements} {incr j} {
$rd lpush biglist1 $val
$rd lpush biglist2 $val
}
for {set j 0} {$j < 500000} {incr j} {
for {set j 0} {$j < $elements} {incr j} {
$rd read ; # Discard replies
$rd read ; # Discard replies
}
@ -302,6 +311,8 @@ start_server {tags {"defrag"}} {
# test the the fragmentation is lower
after 120 ;# serverCron only updates the info once in 100ms
set misses [s active_defrag_misses]
set hits [s active_defrag_hits]
set frag [s allocator_frag_ratio]
set max_latency 0
foreach event [r latency latest] {
@ -312,6 +323,8 @@ start_server {tags {"defrag"}} {
}
if {$::verbose} {
puts "frag $frag"
puts "misses: $misses"
puts "hits: $hits"
puts "max latency $max_latency"
puts [r latency latest]
puts [r latency history active-defrag-cycle]
@ -320,6 +333,10 @@ start_server {tags {"defrag"}} {
# due to high fragmentation, 100hz, and active-defrag-cycle-max set to 75,
# we expect max latency to be not much higher than 7.5ms but due to rare slowness threshold is set higher
assert {$max_latency <= 30}
# in extreme cases of stagnation, we see over 20m misses before the tests aborts with "defrag didn't stop",
# in normal cases we only see 100k misses out of 500k elements
assert {$misses < $elements}
}
# verify the data isn't corrupted or changed
set newdigest [r debug digest]
@ -327,6 +344,110 @@ start_server {tags {"defrag"}} {
r save ;# saving an rdb iterates over all the data / pointers
r del biglist1 ;# coverage for quicklistBookmarksClear
} {1}
test "Active defrag edge case" {
# there was an edge case in defrag where all the slabs of a certain bin are exact the same
# % utilization, with the exception of the current slab from which new allocations are made
# if the current slab is lower in utilization the defragger would have ended up in stagnation,
# keept running and not move any allocation.
# this test is more consistent on a fresh server with no history
start_server {tags {"defrag"}} {
r flushdb
r config resetstat
r config set save "" ;# prevent bgsave from interfereing with save below
r config set hz 100
r config set activedefrag no
r config set active-defrag-max-scan-fields 1000
r config set active-defrag-threshold-lower 5
r config set active-defrag-cycle-min 65
r config set active-defrag-cycle-max 75
r config set active-defrag-ignore-bytes 1mb
r config set maxmemory 0
set expected_frag 1.3
r debug mallctl-str thread.tcache.flush VOID
# fill the first slab containin 32 regs of 640 bytes.
for {set j 0} {$j < 32} {incr j} {
r setrange "_$j" 600 x
r debug mallctl-str thread.tcache.flush VOID
}
# add a mass of keys with 600 bytes values, fill the bin of 640 bytes which has 32 regs per slab.
set rd [redis_deferring_client]
set keys 640000
for {set j 0} {$j < $keys} {incr j} {
$rd setrange $j 600 x
}
for {set j 0} {$j < $keys} {incr j} {
$rd read ; # Discard replies
}
# create some fragmentation of 50%
set sent 0
for {set j 0} {$j < $keys} {incr j 1} {
$rd del $j
incr sent
incr j 1
}
for {set j 0} {$j < $sent} {incr j} {
$rd read ; # Discard replies
}
# create higher fragmentation in the first slab
for {set j 10} {$j < 32} {incr j} {
r del "_$j"
}
# start defrag
after 120 ;# serverCron only updates the info once in 100ms
set frag [s allocator_frag_ratio]
if {$::verbose} {
puts "frag $frag"
}
assert {$frag >= $expected_frag}
set digest [r debug digest]
catch {r config set activedefrag yes} e
if {![string match {DISABLED*} $e]} {
# wait for the active defrag to start working (decision once a second)
wait_for_condition 50 100 {
[s active_defrag_running] ne 0
} else {
fail "defrag not started."
}
# wait for the active defrag to stop working
wait_for_condition 500 100 {
[s active_defrag_running] eq 0
} else {
after 120 ;# serverCron only updates the info once in 100ms
puts [r info memory]
puts [r info stats]
puts [r memory malloc-stats]
fail "defrag didn't stop."
}
# test the the fragmentation is lower
after 120 ;# serverCron only updates the info once in 100ms
set misses [s active_defrag_misses]
set hits [s active_defrag_hits]
set frag [s allocator_frag_ratio]
if {$::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