Re: fdatasync performance problem with large number of DB files

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>
Cc: Justin Pryzby <pryzby(at)telsasoft(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, Paul Guo <guopa(at)vmware(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Brown <michael(dot)brown(at)discourse(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: fdatasync performance problem with large number of DB files
Date: 2021-06-22 04:45:24
Message-ID: YNFq5CnFV/HE4Giy@paquier.xyz
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On Fri, Jun 18, 2021 at 06:18:59PM +0900, Fujii Masao wrote:
> On 2021/06/04 23:39, Justin Pryzby wrote:
>> You said switching to SIGHUP "would have zero effect"; but, actually it allows
>> an admin who's DB took a long time in recovery/startup to change the parameter
>> without shutting down the service. This mitigates the downtime if it crashes
>> again. I think that's at least 50% of how this feature might end up being
>> used.
>
> Yes, it would have an effect when the server is automatically restarted
> after crash when restart_after_crash is enabled. At least for me +1 to
> your proposed change.

Good point about restart_after_crash, I did not consider that.
Switching recovery_init_sync_method to SIGHUP could be helpful with
that.
--
Michael

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