Re: BUG #18385: Assert("strategy_delta >= 0") in BgBufferSync() fails due to race condition

Hi Alexander,
I haven't been able to reproduce this issue on my machine(2 vCPU, 2GB
memory).

Can you reproduce this issue reliably on your machine?

PG Bug reporting form <noreply(at)postgresql(dot)org> 于2024年3月11日周一 03:08写道：

> The following bug has been logged on the website:
>
> Bug reference: 18385
> Logged by: Alexander Lakhin
> Email address: exclusion(at)gmail(dot)com
> PostgreSQL version: 16.2
> Operating system: Ubuntu 22.04
> Description:
>
> With a small shared_buffers value and a short bgwriter_delay:
> shared_buffers = '1MB'
> bgwriter_delay = 10
>
> processing concurrent writing workload like:
> pgbench -i
> pgbench -t 10000 -c 40
>
> on a slow machine leads to:
> number of transactions actually processed: 103642/400000
> ...
> tps = 187.796284 (without initial connection time)
> pgbench: error: Run was aborted; the above results are incomplete.
> ...
> TRAP: failed Assert("strategy_delta >= 0"), File: "bufmgr.c", Line: 2836,
> PID: 20941
> postgres: background writer (ExceptionalCondition+0x52)[0x5581a8dd1677]
> postgres: background writer (BgBufferSync+0xb6)[0x5581a8c5b97a]
> postgres: background writer (BackgroundWriterMain+0x20b)[0x5581a8bf117a]
> postgres: background writer (AuxiliaryProcessMain+0x175)[0x5581a8befa29]
> postgres: background writer (+0x423cff)[0x5581a8bf5cff]
> postgres: background writer (PostmasterMain+0x1127)[0x5581a8bf916f]
> postgres: background writer (main+0x227)[0x5581a8b1d4d5]
>
> To ease reproduction, adding the following delay is recommended:
> --- a/src/backend/storage/buffer/freelist.c
> +++ b/src/backend/storage/buffer/freelist.c
> @@ -417,2 +417,3 @@ StrategySyncStart(...)
> }
> +pg_usleep(300);
> SpinLockRelease(&StrategyControl->buffer_strategy_lock);
>
> (Initially observed during the test 027_stream_regress (which runs with
> shared_buffers = '1MB') with the minimal bgwriter_delay on a slow
> dual-core machine, where one test run takes around 1000 sec.)
>
> Reproduced on REL_12_STABLE .. master. In fact, the issue reproduced
> starting from d72731a70.
>
>

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