From: Davidlohr Bueso <davidlohr@hp.com>
To: Khalid Aziz <khalid.aziz@oracle.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
peterz@infradead.org, akpm@linux-foundation.org,
andi.kleen@intel.com, rob@landley.net, viro@zeniv.linux.org.uk,
oleg@redhat.com, venki@google.com, linux-kernel@vger.kernel.org
Subject: Re: [RFC] [PATCH] Pre-emption control for userspace
Date: Tue, 25 Mar 2014 16:01:07 -0700 [thread overview]
Message-ID: <1395788467.2480.6.camel@buesod1.americas.hpqcorp.net> (raw)
In-Reply-To: <1393870033-31076-1-git-send-email-khalid.aziz@oracle.com>
On Mon, 2014-03-03 at 11:07 -0700, Khalid Aziz wrote:
> I am working on a feature that has been requested by database folks that
> helps with performance. Some of the oft executed database code uses
> mutexes to lock other threads out of a critical section. They often see
> a situation where a thread grabs the mutex, runs out of its timeslice
> and gets switched out which then causes another thread to run which
> tries to grab the same mutex, spins for a while and finally gives up.
> This can happen with multiple threads until original lock owner gets the
> CPU again and can complete executing its critical section. This queueing
> and subsequent CPU cycle wastage can be avoided if the locking thread
> could request to be granted an additional timeslice if its current
> timeslice runs out before it gives up the lock. Other operating systems
> have implemented this functionality and is used by databases as well as
> JVM. This functionality has been shown to improve performance by 3%-5%.
>
> I have implemented similar functionality for Linux. This patch adds a
> file /proc/<tgid>/task/<tid>/sched_preempt_delay for each thread.
> Writing 1 to this file causes CFS scheduler to grant additional time
> slice if the currently running process comes up for pre-emption. Writing
> to this file needs to be very quick operation, so I have implemented
> code to allow mmap'ing /proc/<tgid>/task/<tid>/sched_preempt_delay. This
> allows a userspace task to write this flag very quickly. Usage model is
> a thread mmaps this file during initialization. It then writes a 1 to
> the mmap'd file after it grabs the lock in its critical section where it
> wants immunity from pre-emption. It then writes 0 again to this file
> after it releases the lock and calls sched_yield() to give up the
> processor. I have also added a new field in scheduler statistics -
> nr_preempt_delayed, that counts the number of times a thread has been
> granted amnesty. Further details on using this functionality are in
> Documentation/scheduler/sched-preempt-delay.txt in the patch. This
> patch is based upon the work Venkatesh Pallipadi had done couple of
> years ago.
>
> Please provide feedback on this functionality and patch.
Good timing! The topic came up just yesterday in LSF/MM. This
functionality is on the wish list for both facebook and postgres.
next prev parent reply other threads:[~2014-03-25 23:01 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-03 18:07 [RFC] [PATCH] Pre-emption control for userspace Khalid Aziz
2014-03-03 21:51 ` Davidlohr Bueso
2014-03-03 23:29 ` Khalid Aziz
2014-03-04 13:56 ` Oleg Nesterov
2014-03-04 17:44 ` Khalid Aziz
2014-03-04 18:38 ` Al Viro
2014-03-04 19:01 ` Khalid Aziz
2014-03-04 19:03 ` Oleg Nesterov
2014-03-04 20:14 ` Khalid Aziz
2014-03-05 14:38 ` Oleg Nesterov
2014-03-05 16:12 ` Oleg Nesterov
2014-03-05 17:10 ` Khalid Aziz
2014-03-04 21:12 ` H. Peter Anvin
2014-03-04 21:39 ` Khalid Aziz
2014-03-04 22:23 ` One Thousand Gnomes
2014-03-04 22:44 ` Khalid Aziz
2014-03-05 0:39 ` Thomas Gleixner
2014-03-05 0:51 ` Andi Kleen
2014-03-05 11:10 ` Peter Zijlstra
2014-03-05 17:29 ` Khalid Aziz
2014-03-05 19:58 ` Khalid Aziz
2014-03-06 9:57 ` Peter Zijlstra
2014-03-06 16:08 ` Khalid Aziz
2014-03-06 11:14 ` Thomas Gleixner
2014-03-06 16:32 ` Khalid Aziz
2014-03-05 14:54 ` Oleg Nesterov
2014-03-05 15:56 ` Andi Kleen
2014-03-05 16:36 ` Oleg Nesterov
2014-03-05 17:22 ` Khalid Aziz
2014-03-05 23:13 ` David Lang
2014-03-05 23:48 ` Khalid Aziz
2014-03-05 23:56 ` H. Peter Anvin
2014-03-06 0:02 ` Khalid Aziz
2014-03-06 0:13 ` H. Peter Anvin
2014-03-05 23:59 ` David Lang
2014-03-06 0:17 ` Khalid Aziz
2014-03-06 0:36 ` David Lang
2014-03-06 1:22 ` Khalid Aziz
2014-03-06 14:23 ` David Lang
2014-03-06 12:13 ` Kevin Easton
2014-03-06 13:59 ` Peter Zijlstra
2014-03-06 22:41 ` Andi Kleen
2014-03-06 14:25 ` David Lang
2014-03-06 16:12 ` Khalid Aziz
2014-03-06 13:24 ` Rasmus Villemoes
2014-03-06 13:34 ` Peter Zijlstra
2014-03-06 13:45 ` Rasmus Villemoes
2014-03-06 14:02 ` Peter Zijlstra
2014-03-06 14:33 ` Thomas Gleixner
2014-03-06 14:34 ` H. Peter Anvin
2014-03-06 14:04 ` Thomas Gleixner
2014-03-25 17:17 ` [PATCH v2] " Khalid Aziz
2014-03-25 17:44 ` Andrew Morton
2014-03-25 17:56 ` Khalid Aziz
2014-03-25 18:14 ` Andrew Morton
2014-03-25 17:46 ` Oleg Nesterov
2014-03-25 17:59 ` Khalid Aziz
2014-03-25 18:20 ` Andi Kleen
2014-03-25 18:47 ` Khalid Aziz
2014-03-25 19:47 ` Andi Kleen
2014-03-25 18:59 ` Eric W. Biederman
2014-03-25 19:15 ` Khalid Aziz
2014-03-25 20:31 ` Eric W. Biederman
2014-03-25 21:37 ` Khalid Aziz
2014-03-26 6:03 ` Mike Galbraith
2014-03-25 23:01 ` Davidlohr Bueso [this message]
2014-03-25 23:29 ` [RFC] [PATCH] " Khalid Aziz
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