| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>, ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: sync_file_range() |
| Date: | 2006-06-19 19:53:32 |
| Message-ID: | 1150746813.2587.98.camel@localhost.localdomain |
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| Thread: | |
| Lists: | pgsql-hackers |
On Mon, 2006-06-19 at 15:04 -0400, Greg Stark wrote:
> > We fsync the xlog at transaction commit, so only the leading edge needs
> > to be synced - would the call help there? Presumably the OS can already
> > locate all blocks associated with a particular file fairly quickly
> > without doing a full cache scan.
>
> Well in theory the transaction being committed isn't necessarily the "leading
> edge", there could be more work from other transactions since the last work
> this transaction actually did.
Near enough.
> > Other files are fsynced at checkpoint - always all dirty blocks in the
> > whole file.
>
> Well couldn't it be useful for checkpoints if it there was some way to know
> which buffers had been touched since the last checkpoint? There could be a lot
> of buffers dirtied since the checkpoint began and those don't really need to
> be synced do they?
Qingqing had a proposal for something like that, but seemed not worth it
after analysis.
--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com
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