----- Original Message -----
From: "John Baldwin" <[email protected]>
On Wednesday, July 17, 2013 3:18:52 pm Konstantin Belousov wrote:
On Wed, Jul 17, 2013 at 02:07:55PM -0400, Mark Johnston wrote:
> During such an fsync, DTrace shows me that syncer sleeps of 50-200ms are
> happening up to 8 or 10 times a second. When this happens, a bunch of
> postgres threads become blocked in vn_write() waiting for the vnode lock
> to become free. It looks like the write-clustering code is limited to
> using (nswbuf / 2) pbufs, and FreeBSD prevents one from setting nswbuf
> to anything greater than 256.
Syncer is probably just a victim of profiling. Would postgres called
fsync(2), you then blame the fsync code for the pauses.
Just add a tunable to allow the user to manually-tune the nswbuf,
regardless of the buffer cache sizing. And yes, nswbuf default max
probably should be bumped to something like 1024, at least on 64bit
architectures which do not starve for kernel memory.
Also, if you are seeing I/O stalls with mfi(4), then you might need a
firmware update for your mfi(4) controller. cc'ing smh@ who knows more about
that particular issue (IIRC).
Indeed if your seeing any IO timeouts in /var/log/messages or the console
there is a know issue in older mfi(4) firmware which can cause extended
IO stalls.
We believe that fixed firmware packages include "APP" version > *.130.*
For Dell branded HW that corrisponds with FW package version 21.2.1-0000
Regards
Steve
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