BDR, wal sender, high system cpu, mutex_lock_common
Hi all,
I've an environment 9.4 + bdr:
PostgreSQL 9.4.4 on x86_64-unknown-linux-gnu, compiled by gcc (Debian
4.7.2-5) 4.7.2, 64-bit
kernel version:
3.2.0-4-amd64 #1 SMP Debian 3.2.65-1 x86_64 GNU/Linux
This is consolidation databases, in this machine there are around 250+ wal
sender processes.
top output revealed high system cpu:
%Cpu(s): 1.4 us, 49.7 sy, 0.0 ni, 48.8 id, 0.0 wa, 0.0 hi, 0.0 si,
0.0 st
profiling cpu with perf:
perf top -e cpu-clock
Events: 142K cpu-clock
82.37% [kernel] [k] __mutex_lock_common.isra.5
4.49% [kernel] [k] do_raw_spin_lock
2.23% [kernel] [k] mutex_lock
2.16% [kernel] [k] mutex_unlock
2.12% [kernel] [k] arch_local_irq_restore
1.73% postgres [.] ValidXLogRecord
0.87% [kernel] [k] __mutex_unlock_slowpath
0.78% [kernel] [k] arch_local_irq_enable
0.63% [kernel] [k] sys_recvfrom
finally get which processes (wal senders) that are using mutexes:
perf top -e task-clock -p 55382
Events: 697 task-clock
88.08% [kernel] [k] __mutex_lock_common.isra.5
3.27% [kernel] [k] do_raw_spin_lock
2.34% [kernel] [k] arch_local_irq_restore
2.10% postgres [.] ValidXLogRecord
1.87% [kernel] [k] mutex_unlock
1.87% [kernel] [k] mutex_lock
0.47% [kernel] [k] sys_recvfrom
strace output of wal sender process:
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
98.30 1.030072 5 213063 201463 read
1.69 0.017686 0 201464 201464 recvfrom
0.01 0.000110 0 806 lseek
0.00 0.000043 0 474 468 rt_sigreturn
0.00 0.000000 0 6 open
0.00 0.000000 0 6 close
------ ----------- ----------- --------- --------- ----------------
100.00 1.047911 415819 403395 total
strace detail, majority read from pipe and recvfrom from socket (but most
of them are EAGAIN):
read(15, "~\320\5\0\1\0\0\0\0@\235\1\360\16\0\0\334\26\0\0\0\0\0\0\365\27\0\0\0\0\0\0"...,
8192) = 8192 <0.000025>
read(6, 0x7fffdd837b3f, 1) = -1 EAGAIN (Resource temporarily unavailable)
<0.000116>
recvfrom(10, 0x7fffdd837b17, 1, 0, 0, 0) = -1 EAGAIN (Resource temporarily
unavailable) <0.000049>
ls -l /proc/62388/fd/15
lr-x------ 1 postgres postgres 64 Oct 1 08:39 /proc/62388/fd/15 ->
/data/pg_xlog/0000000100000EF000000061
ls -l /proc/62388/fd/6
lr-x------ 1 postgres postgres 64 Oct 1 08:39 /proc/62388/fd/6 ->
pipe:[1090892506]
ls -l /proc/62388/fd/10
lrwx------ 1 postgres postgres 64 Oct 1 08:39 /proc/62388/fd/10 ->
socket:[1096584060]
I wonder, is there kernel version has better handling mutexes?
Or is it the expected behavior?
Sorry for cross-posting, I have posted the same on pgsql-performance too....
--
regards
ujang jaenudin | DBA Consultant (Freelancer)
http://ora62.wordpress.com
http://id.linkedin.com/pub/ujang-jaenudin/12/64/bab
On 3 October 2017 at 19:45, milist ujang <ujang.milist@gmail.com> wrote:
Hi all,
I've an environment 9.4 + bdr:
PostgreSQL 9.4.4
You're on a pretty old postgres-bdr. Update. You're missing a lot of fixes
from mainline.
This is consolidation databases, in this machine there are around 250+ wal
sender processes.
Not a great use case for BDR.
Consider pglogical.
finally get which processes (wal senders) that are using mutexes:
perf top -e task-clock -p 55382
Can you get stacks please?
Use -g
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
Hi Craig,
Anyway, this OS is guess OS in vmware (vsphere).
Thank for your response and help.
On Tue, Oct 3, 2017 at 8:49 PM, Craig Ringer <craig@2ndquadrant.com> wrote:
Can you get stacks please?
Use -g
# Events: 2K cpu-clock
#
# Overhead Command Shared Object Symbol
# ........ ........ ................. ............................
#
86.96% postgres [kernel.kallsyms] [k] __mutex_lock_common.isra.5
|
--- __mutex_lock_common.isra.5
read 2.85% postgres [kernel.kallsyms] [k] do_raw_spin_lock
|
--- do_raw_spin_lock
|
|--90.48%-- read
|
|--8.33%-- recv
|
--1.19%-- write 2.44% postgres [kernel.kallsyms] [k] mutex_unlock
|
--- mutex_unlock
read 2.03% postgres [kernel.kallsyms] [k] arch_local_irq_restore
|
--- arch_local_irq_restore
read 1.32% postgres postgres [.] ValidXLogRecord
|
--- ValidXLogRecord 1.25% postgres [kernel.kallsyms] [k] mutex_lock
|
--- mutex_lock
read--
regards
ujang jaenudin | DBA Consultant (Freelancer)
http://ora62.wordpress.com
http://id.linkedin.com/pub/ujang-jaenudin/12/64/bab
On 4 October 2017 at 00:21, milist ujang <ujang.milist@gmail.com> wrote:
On Tue, Oct 3, 2017 at 8:49 PM, Craig Ringer <craig@2ndquadrant.com> wrote:
Can you get stacks please?
Use -g
# Events: 2K cpu-clock # # Overhead Command Shared Object Symbol # ........ ........ ................. ............................ # 86.96% postgres [kernel.kallsyms] [k] __mutex_lock_common.isra.5 | --- __mutex_lock_common.isra.5 read
Unfortunately it looks like you're using a postgres built with
-fomit-frame-pointers (the default) on x64, with an older perf not
built with libunwind. This produces useless stacks.
You may need to recompile with -fno-omit-frame-pointer
--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general
On 2017-10-12 10:25:43 +0800, Craig Ringer wrote:
On 4 October 2017 at 00:21, milist ujang <ujang.milist@gmail.com> wrote:
On Tue, Oct 3, 2017 at 8:49 PM, Craig Ringer <craig@2ndquadrant.com> wrote:
Can you get stacks please?
Use -g
# Events: 2K cpu-clock # # Overhead Command Shared Object Symbol # ........ ........ ................. ............................ # 86.96% postgres [kernel.kallsyms] [k] __mutex_lock_common.isra.5 | --- __mutex_lock_common.isra.5 readUnfortunately it looks like you're using a postgres built with
-fomit-frame-pointers (the default) on x64, with an older perf not
built with libunwind. This produces useless stacks.
Just read this mail, but for libunwind to work you'd have to specify
"--call-graph dwarf", no?
- Andres
--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general
On 12 October 2017 at 11:03, Andres Freund <andres@anarazel.de> wrote:
On 2017-10-12 10:25:43 +0800, Craig Ringer wrote:
On 4 October 2017 at 00:21, milist ujang <ujang.milist@gmail.com> wrote:
On Tue, Oct 3, 2017 at 8:49 PM, Craig Ringer <craig@2ndquadrant.com> wrote:
Can you get stacks please?
Use -g
# Events: 2K cpu-clock # # Overhead Command Shared Object Symbol # ........ ........ ................. ............................ # 86.96% postgres [kernel.kallsyms] [k] __mutex_lock_common.isra.5 | --- __mutex_lock_common.isra.5 readUnfortunately it looks like you're using a postgres built with
-fomit-frame-pointers (the default) on x64, with an older perf not
built with libunwind. This produces useless stacks.Just read this mail, but for libunwind to work you'd have to specify
"--call-graph dwarf", no?
I think you're right. But only on a version of perf where it's
available and used.
I haven't recently checked if perf has finally grown the ability to
load external debug symbols either. It never used to.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general