MINOR: proxy/pool: prevent unnecessary calls to pool_gc()
Under certain soft-stopping conditions (ie: sticktable attached to proxy
and in-progress connections to the proxy that prevent haproxy from
exiting), manage_proxy() (p->task) will wake up every second to perform
a cleanup attempt on the proxy sticktable (to purge unused entries).
However, as reported by TimWolla in GH #2091, it was found that a
systematic call to pool_gc() could cause some CPU waste, mainly
because malloc_trim() (which is rather expensive) is being called
for each pool_gc() invocation.
As a result, such soft-stopping process could be spending a significant
amount of time in the malloc_trim->madvise() syscall for nothing.
Example "strace -c -f -p `pidof haproxy`" output (taken from
Tim's report):
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
46.77 1.840549 3941 467 1 epoll_wait
43.82 1.724708 13 128509 sched_yield
8.82 0.346968 11 29696 madvise
0.58 0.023011 24 951 clock_gettime
0.01 0.000257 10 25 7 recvfrom
0.00 0.000033 11 3 sendto
0.00 0.000021 21 1 rt_sigreturn
0.00 0.000021 21 1 timer_settime
------ ----------- ----------- --------- --------- ----------------
100.00 3.935568 24 159653 8 total
To prevent this, we now only call pool_gc() when some memory is
really expected to be reclaimed as a direct result of the previous
stick table cleanup.
This is pretty straightforward since stktable_trash_oldest() returns
the number of trashed sticky sessions.
This may be backported to every stable versions.
(cherry picked from commit 6e1fe253b71707cfe58ab2c7e15d8e36976fd565)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit c4ab8c490ec5ff0152ad672d694b718d9c2b0d3d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit c2c2ac7195a2d8fe4075ff90b56cd56e490b7838)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 05aaac3fa371aa979c52152cc2fea96abc066c47)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
1 file changed