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Re: Fix overflow of bgwriter's request queue

From: ITAGAKI Takahiro <itagaki(dot)takahiro(at)lab(dot)ntt(dot)co(dot)jp>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-patches(at)postgresql(dot)org
Cc: "Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu>
Subject: Re: Fix overflow of bgwriter's request queue
Date: 2006-01-16 02:00:33
Message-ID: 20060116095906.4BD5.ITAGAKI.TAKAHIRO@lab.ntt.co.jp (view raw or flat)
Thread:
Lists: pgsql-patches
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> > "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)lab(dot)ntt(dot)co(dot)jp> wrote
> >> AbsorbFsyncRequests will be called during the fsync loop in my patch,
> >> so new files might be added to pendingOpsTable and they will be removed
> >> from the table *before* writing the pages belonging to them.
> 
> I think this fear is incorrect.  At the time ForwardFsyncRequest is
> called, the backend must *already* have done whatever write it is
> concerned about fsync'ing.

Oops, I was wrong. Also, I see that there is no necessity for fearing
endless loops because hash-seqscan and HASH_ENTER don't conflict.

Attached is a revised patch. It became very simple, but I worry that
one magic number (BUFFERS_PER_ABSORB) is still left.

---
ITAGAKI Takahiro
NTT Cyber Space Laboratories


Attachment: bgwriter-requests-queue-overflow-3.patch
Description: application/octet-stream (2.3 KB)

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