| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Joachim Wieland <joe(at)mcknight(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: posix_fadvise missing in the walsender |
| Date: | 2013-02-21 17:28:21 |
| Message-ID: | CA+TgmobgNgDTU3YzZ=iaRjUgFvQcLbVS5Yd9V41PKh0g=fZLfg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Feb 21, 2013 at 12:16 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> Does the kernel really read a data block from disk into memory in
> order to immediately overwrite it? I would have thought it would
> optimize that away, at least if the writes are sized and aligned to
> 512 or 1024 bytes blocks (which WAL should be).
Now that you mention that I agree it seems strange, but that's what I saw.
/me scratches head
It does seem pretty odd, though.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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