From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Peter Eisentraut <peter_e(at)gmx(dot)net> |
Subject: | Re: initdb and fsync |
Date: | 2012-07-13 23:43:14 |
Message-ID: | 28922.1342222994@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> One point about the commit message: fadvise does not block to go into
> the request queue, sync_file_range does. The problem with fadvise is
> that, when the request queue is small, it fills up so fast that most of
> the requests never make it in, and fadvise is essentially a no-op.
> sync_file_range waits for room in the queue, which is (based on my
> tests) enough to improve the scheduling a lot.
I see. I misunderstood your previous message. In that case, it seems
quite likely that it might be helpful if copy_file were to aggregate
the fadvise/sync_file_range calls over larger pieces of the file.
(I'm assuming that the request queue isn't bright enough to aggregate
by itself, though that might be wrong.)
regards, tom lane
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