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improve the stability and correctness of "Test child sending info" (#9562)

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Since we measure the COW size in this test by changing some keys and reading
the reported COW size, we need to ensure that the "dismiss mechanism" (#8974)
will not free memory and reduce the COW size.

For that, this commit changes the size of the keys to 512B (less than a page).
and because some keys may fall into the same page, we are modifying ten keys
on each iteration and check for at least 50% change in the COW size.
This commit is contained in:
YaacovHazan 2021-10-04 10:32:26 +03:00 committed by GitHub
parent 6f4f31f167
commit 5becb7c9c6
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 16 additions and 5 deletions
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21
tests/integration/rdb.tcl
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@ -228,7 +228,8 @@ start_server {} {
# Our COW metrics (Private_Dirty) work only on Linux
set system_name [string tolower [exec uname -s]]
if {$system_name eq {linux}} {
set page_size [exec getconf PAGESIZE]
if {$system_name eq {linux} && $page_size == 4096} {
start_server {overrides {save ""}} {
test {Test child sending info} {
@ -245,9 +246,11 @@ start_server {overrides {save ""}} {
r config set rdb-key-save-delay 200
r config set loglevel debug
# populate the db with 10k keys of 4k each
# populate the db with 10k keys of 512B each (since we want to measure the COW size by
# changing some keys and read the reported COW size, we are using small key size to prevent from
# the "dismiss mechanism" free memory and reduce the COW size)
set rd [redis_deferring_client 0]
set size 4096
set size 500 ;# aim for the 512 bin (sds overhead)
set cmd_count 10000
for {set k 0} {$k < $cmd_count} {incr k} {
$rd set key$k [string repeat A $size]
@ -270,6 +273,7 @@ start_server {overrides {save ""}} {
# on each iteration, we will write some key to the server to trigger copy-on-write, and
# wait to see that it reflected in INFO.
set iteration 1
set key_idx 0
while 1 {
# take samples before writing new data to the server
set cow_size [s current_cow_size]
@ -283,12 +287,19 @@ start_server {overrides {save ""}} {
}
# trigger copy-on-write
r setrange key$iteration 0 [string repeat B $size]
set modified_keys 16
for {set k 0} {$k < $modified_keys} {incr k} {
r setrange key$key_idx 0 [string repeat B $size]
incr key_idx 1
}
# changing 16 keys (512B each) will create at least 8192 COW (2 pages), but we don't want the test
# to be too strict, so we check for a change of at least 4096 bytes
set exp_cow [expr $cow_size + 4096]
# wait to see that current_cow_size value updated (as long as the child is in progress)
wait_for_condition 80 100 {
[s rdb_bgsave_in_progress] == 0 ||
[s current_cow_size] >= $cow_size + $size &&
[s current_cow_size] >= $exp_cow &&
[s current_save_keys_processed] > $keys_processed &&
[s current_fork_perc] > 0
} else {