| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Teodor Sigaev <teodor(at)sigaev(dot)ru> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Re: [COMMITTERS] pgsql: Correctly align page's images in generic wal API |
| Date: | 2016-05-17 15:35:46 |
| Message-ID: | 1146.1463499346@sss.pgh.pa.us |
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Teodor Sigaev <teodor(at)sigaev(dot)ru> writes:
>> Instead of allocating this memory unconditionally for each buffer,
>> wouldn't it be better to set all the page pointers to NULL in
>> GenericXLogStart and allocate memory only once a buffer is registered
>> in GenericXLogRegisterBuffer when finding a free slot? This patch is
>> wasting many cycles.
> GenericXLogRegisterBuffer() could be called in another MemoryContext what
> can be a reason for strange bugs. Right now only a few pages could be
> involved in one round of GenericWal. I don't believe that such allocation
> could be a reason of noticable performance degradation. Although I didn't
> check that.
You could allocate all the pages in one palloc, though, and then just
set the pointers via address arithmetic.
regards, tom lane
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