From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> |
Cc: | Greg Smith <gsmith(at)gregsmith(dot)com>, pgsql-patches(at)postgresql(dot)org |
Subject: | Re: Sorting writes during checkpoint |
Date: | 2008-05-04 04:40:19 |
Message-ID: | 4421.1209876019@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-patches |
ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> Greg Smith <gsmith(at)gregsmith(dot)com> wrote:
>> If shared_buffers(=NBuffers) is set to something big, this could give some
>> memory churn. And I think it's a bad idea to allocate something this
>> large at checkpoint time, because what happens if that fails? Really not
>> the time you want to discover there's no RAM left.
> Hmm, but I think we need to copy buffer tags into bgwriter's local memory
> in order to avoid locking taga many times in the sorting.
I updated this patch to permanently allocate the working array as Greg
suggests, and to fix a bunch of commenting issues (attached).
However, I am completely unable to measure any performance improvement
from it. Given the possible risk of out-of-memory failures, I think the
patch should not be applied without some direct proof of performance
benefits, and I don't see any.
regards, tom lane
Attachment | Content-Type | Size |
---|---|---|
unknown_filename | text/plain | 7.1 KB |
From | Date | Subject | |
---|---|---|---|
Next Message | Euler Taveira de Oliveira | 2008-05-04 05:21:41 | Re: Patch for Prevent pg_dump/pg_restore from being affected by statement_timeout |
Previous Message | Tom Lane | 2008-05-04 00:55:31 | Re: [HACKERS] Multiline privileges in \z |
From | Date | Subject | |
---|---|---|---|
Next Message | Euler Taveira de Oliveira | 2008-05-04 05:21:41 | Re: Patch for Prevent pg_dump/pg_restore from being affected by statement_timeout |
Previous Message | Tom Lane | 2008-05-04 00:55:31 | Re: [HACKERS] Multiline privileges in \z |