From: | Scott Carey <scott(at)richrelevance(dot)com> |
---|---|
To: | Mladen Gogala <mladen(dot)gogala(at)vmsinfo(dot)com> |
Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Defaulting wal_sync_method to fdatasync on Linux for 9.1? |
Date: | 2010-11-17 19:26:30 |
Message-ID: | B934F82D-E22F-42E7-A69D-A9C409C96DBE@richrelevance.com |
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Thread: | |
Lists: | pgsql-performance |
On Nov 16, 2010, at 4:05 PM, Mladen Gogala wrote:
> Josh Berkus wrote:
>> On 11/16/10 12:39 PM, Greg Smith wrote:
>>
>>> I want to next go through and replicate some of the actual database
>>> level tests before giving a full opinion on whether this data proves
>>> it's worth changing the wal_sync_method detection. So far I'm torn
>>> between whether that's the right approach, or if we should just increase
>>> the default value for wal_buffers to something more reasonable.
>>>
>>
>> We'd love to, but wal_buffers uses sysV shmem.
>>
>>
> Speaking of the SYSV SHMEM, is it possible to use huge pages?
RHEL 6 and friends have transparent hugepage support. I'm not sure if they yet transparently do it for SYSV SHMEM, but they do for most everything else. Sequential traversal of a process heap is several times faster with hugepages. Unfortunately, postgres doesn't organize its blocks in its shared_mem to be sequential for a relation. So it might not matter much.
>
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>
> Mladen Gogala
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