From: Chris Mason <chris.mason@fusionio.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rik van Riel <riel@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Waiman Long <Waiman.Long@hp.com>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Emmanuel Benisty <benisty.e@gmail.com>,
"Vinod, Chegu" <chegu_vinod@hp.com>,
"Low, Jason" <jason.low2@hp.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
"aquini@redhat.com" <aquini@redhat.com>,
Michel Lespinasse <walken@google.com>,
Ingo Molnar <mingo@kernel.org>,
Larry Woodman <lwoodman@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Chris Mason <clmason@fusionio.com>, <dave.kleikamp@oracle.com>
Subject: Re: [PATCH v2 0/4] ipc: reduce ipc lock contention
Date: Thu, 7 Mar 2013 07:55:46 -0500 [thread overview]
Message-ID: <20130307125546.GD13323@shiny.masoncoding.com> (raw)
In-Reply-To: <1362645933.2606.14.camel@laptop>
On Thu, Mar 07, 2013 at 01:45:33AM -0700, Peter Zijlstra wrote:
> On Tue, 2013-03-05 at 15:53 -0500, Rik van Riel wrote:
>
> > Indeed. Though how well my patches will work with Oracle will
> > depend a lot on what kind of semctl syscalls they are doing.
> >
> > Does Oracle typically do one semop per semctl syscall, or does
> > it pass in a whole bunch at once?
>
> https://oss.oracle.com/~mason/sembench.c
>
> I think Chris wrote that to match a particular pattern of semaphore
> operations the database engine in question does. I haven't checked to
> see if it triggers the case in point though.
>
> Also, Chris since left Oracle but maybe he knows who to poke.
>
Dave Kleikamp (cc'd) took over my patches and did the most recent
benchmarking. Ported against 3.0:
https://oss.oracle.com/git/?p=linux-uek-2.6.39.git;a=commit;h=c7fa322dd72b08450a440ef800124705a1fa148c
The current versions are still in the 2.6.32 oracle kernel, but it looks
like they reverted this 3.0 commit. I think with Manfred's upstream
work my more complex approach wasn't required anymore, but hopefully
Dave can fill in details.
Here is some of the original discussion around the patch:
https://lkml.org/lkml/2010/4/12/257
In terms of how oracle uses IPC, the part that shows up in profiles is
using semtimedop for bulk wakeups. They can configure things to use
either a bunch of small arrays or a huge single array (and anything in
between).
There is one IPC semaphore per process and they use this to wait for
some event (like a log commit). When the event comes in, everyone
waiting is woken in bulk via a semtimedop call.
So, single proc waking many waiters at once.
-chris
next prev parent reply other threads:[~2013-03-07 12:55 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-05 9:35 [PATCH v2 0/4] ipc: reduce ipc lock contention Davidlohr Bueso
2013-03-05 15:40 ` Linus Torvalds
2013-03-06 7:13 ` Davidlohr Bueso
2013-03-06 16:01 ` Linus Torvalds
2013-03-05 17:10 ` Rik van Riel
2013-03-05 19:42 ` Waiman Long
2013-03-05 20:52 ` Linus Torvalds
2013-03-05 20:53 ` Rik van Riel
2013-03-06 3:46 ` Waiman Long
2013-03-06 3:53 ` Rik van Riel
2013-03-06 7:14 ` Davidlohr Bueso
2013-03-07 8:45 ` Peter Zijlstra
2013-03-07 12:55 ` Chris Mason [this message]
2013-03-07 15:54 ` Dave Kleikamp
2013-03-07 16:42 ` Chris Mason
2013-03-06 22:13 ` [PATCH v2 5/4] ipc: replace ipc_perm.lock with an rwlock Rik van Riel
2013-03-06 22:14 ` [PATCH v2 6/4] ipc: open code and rename sem_lock Rik van Riel
2013-03-06 22:15 ` [PATCH v2 7/4] ipc: fine grained locking for semtimedop Rik van Riel
2013-03-06 22:57 ` Linus Torvalds
2013-03-06 23:09 ` Rik van Riel
2013-03-07 1:36 ` Davidlohr Bueso
2013-03-07 20:55 ` Rik van Riel
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