spinlocks storm bug
Hello
I have a report of critical bug (database is temporary unavailability ..
restart is necessary).
A customer use:
PostgreSQL 9.2.4,
24 CPU
140G RAM
SSD disc for all
Database is under high load. There is a few databases with very high number
of similar simple statements. When application produce higher load, then
number of active connection is increased to 300-600 about.
In some moment starts described event - there is a minimal IO, all CPU are
on 100%.
Perf result shows:
354246.00 93.0% s_lock
/usr/lib/postgresql/9.2/bin/postgres
10503.00 2.8% LWLockRelease
/usr/lib/postgresql/9.2/bin/postgres
8802.00 2.3% LWLockAcquire
/usr/lib/postgresql/9.2/bin/postgres
828.00 0.2% _raw_spin_lock
[kernel.kallsyms]
559.00 0.1% _raw_spin_lock_irqsave
[kernel.kallsyms]
340.00 0.1% switch_mm
[kernel.kallsyms]
305.00 0.1% poll_schedule_timeout
[kernel.kallsyms]
274.00 0.1% native_write_msr_safe
[kernel.kallsyms]
257.00 0.1% _raw_spin_lock_irq
[kernel.kallsyms]
238.00 0.1% apic_timer_interrupt
[kernel.kallsyms]
236.00 0.1% __schedule
[kernel.kallsyms]
213.00 0.1% HeapTupleSatisfiesMVCC
We try to limit a connection to 300, but I am not sure if this issue is not
related to some Postgres bug.
Regards
Pavel
On 2013-12-06 07:22:27 +0100, Pavel Stehule wrote:
I have a report of critical bug (database is temporary unavailability ..
restart is necessary).
PostgreSQL 9.2.4,
24 CPU
140G RAM
SSD disc for allDatabase is under high load. There is a few databases with very high number
of similar simple statements. When application produce higher load, then
number of active connection is increased to 300-600 about.In some moment starts described event - there is a minimal IO, all CPU are
on 100%.Perf result shows:
354246.00 93.0% s_lock
/usr/lib/postgresql/9.2/bin/postgres
10503.00 2.8% LWLockRelease
/usr/lib/postgresql/9.2/bin/postgres
8802.00 2.3% LWLockAcquire
We try to limit a connection to 300, but I am not sure if this issue is not
related to some Postgres bug.
We've seen this issue repeatedly now. None of the times it turned out to
be a bug, but just limitations in postgres' scalability. If you can I'd
strongly suggest trying to get postgres binaries compiled with
-fno-omit-frame-pointer installed to check which locks are actually
conteded.
My bet is BufMappingLock.
There's a CF entry about changing our lwlock implementation to scale
better...
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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2013/12/6 Andres Freund <andres@2ndquadrant.com>
On 2013-12-06 07:22:27 +0100, Pavel Stehule wrote:
I have a report of critical bug (database is temporary unavailability ..
restart is necessary).PostgreSQL 9.2.4,
24 CPU
140G RAM
SSD disc for allDatabase is under high load. There is a few databases with very high
number
of similar simple statements. When application produce higher load, then
number of active connection is increased to 300-600 about.In some moment starts described event - there is a minimal IO, all CPU
are
on 100%.
Perf result shows:
354246.00 93.0% s_lock
/usr/lib/postgresql/9.2/bin/postgres
10503.00 2.8% LWLockRelease
/usr/lib/postgresql/9.2/bin/postgres
8802.00 2.3% LWLockAcquireWe try to limit a connection to 300, but I am not sure if this issue is
not
related to some Postgres bug.
We've seen this issue repeatedly now. None of the times it turned out to
be a bug, but just limitations in postgres' scalability. If you can I'd
strongly suggest trying to get postgres binaries compiled with
-fno-omit-frame-pointer installed to check which locks are actually
conteded.
My bet is BufMappingLock.There's a CF entry about changing our lwlock implementation to scale
better...
one missing info - the customer's staff reduced shared buffers from 30G to
5G without success. A database is 20G about.
Regards
Pavel
Show quoted text
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services