this is wonderful news.
this is pretty much what we observed as well. the kernel has acted as
showstopper for many setups recently. this patch fixed most cases
related to kernel read ahead and so on for us.
in fact, posix_fadvise was the only way to prevent a big germany
company from replacing postgres with oracle.
the problem was that synchronized scans led to a significant decrease
of I/O throughput as the kernel was simply confused by processes
concurrently reading the same file.
I hope zoltan's autoconf magic fixes the portability issues.
On Jun 20, 2008, at 1:19 AM, Greg Smith wrote:
On Thu, 19 Jun 2008, Zoltan Boszormenyi wrote:
This patch (revisited and ported to current CVS HEAD) is indeed using
Greg's original patch and also added another patch written by Mark
that helps evicting closed XLOGs from memory faster.
Great, that will save me some trouble. I've got a stack of Linux
performance testing queued up (got stuck behind a kernel bug
impacting pgbench) for the next couple of weeks and I'll include
this in that testing. I think I've got a similar class of hardware
as you tested on for initial evaluation--I'm getting around 200MB/s
sequential I/O right now out of my small RAID setup,.
I added your patch to the queue for next month's CommitFest and
listed myself as the initial reviewer, but a commit that soon is
unlikely. Performance tests like this usually take a while to
converge, and since this is using a less popular API I expect a
round of portability concerns, too.
Where did Marc's patch come from? I'd like to be able to separate
out that change from the rest if necessary.
Also, if you have any specific test cases you ran that I could
start by trying to replicate a speedup on, those would be handy as
* Greg Smith [EMAIL PROTECTED] http://www.gregsmith.com
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