From: Rik van Riel <riel@redhat.com>
To: Michel Lespinasse <walken@google.com>
Cc: Alex Shi <alex.shi@intel.com>, Ingo Molnar <mingo@kernel.org>,
David Howells <dhowells@redhat.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>,
Yuanhan Liu <yuanhan.liu@linux.intel.com>,
Peter Hurley <peter@hurleysoftware.com>,
Dave Chinner <david@fromorbit.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 06/13] rwsem: more agressive lock stealing in rwsem_down_write_failed
Date: Thu, 28 Mar 2013 16:54:54 -0400 [thread overview]
Message-ID: <5154AE1E.6000007@redhat.com> (raw)
In-Reply-To: <1363344869-15732-7-git-send-email-walken@google.com>
On 03/15/2013 06:54 AM, Michel Lespinasse wrote:
> Some small code simplifications can be achieved by doing more agressive
> lock stealing:
>
> - When rwsem_down_write_failed() notices that there are no active locks
> (and thus no thread to wake us if we decided to sleep), it used to wake
> the first queued process. However, stealing the lock is also sufficient
> to deal with this case, so we don't need this check anymore.
>
> - In try_get_writer_sem(), we can steal the lock even when the first waiter
> is a reader. This is correct because the code path that wakes readers is
> protected by the wait_lock. As to the performance effects of this change,
> they are expected to be minimal: readers are still granted the lock
> (rather than having to acquire it themselves) when they reach the front
> of the wait queue, so we have essentially the same behavior as in
> rwsem-spinlock.
>
> Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
next prev parent reply other threads:[~2013-03-28 20:56 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-15 10:54 [PATCH v2 00/13] rwsem fast-path write lock stealing Michel Lespinasse
2013-03-15 10:54 ` [PATCH v2 01/13] rwsem: make the waiter type an enumeration rather than a bitmask Michel Lespinasse
2013-03-28 18:59 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 02/13] rwsem: shorter spinlocked section in rwsem_down_failed_common() Michel Lespinasse
2013-03-28 16:21 ` Peter Hurley
2013-03-28 19:03 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 03/13] rwsem: move rwsem_down_failed_common code into rwsem_down_{read,write}_failed Michel Lespinasse
2013-03-28 17:05 ` Peter Hurley
2013-04-27 21:21 ` Davidlohr Bueso
2013-03-28 19:08 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 04/13] rwsem: simplify rwsem_down_read_failed Michel Lespinasse
2013-03-28 19:22 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 05/13] rwsem: simplify rwsem_down_write_failed Michel Lespinasse
2013-03-28 20:33 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 06/13] rwsem: more agressive lock stealing in rwsem_down_write_failed Michel Lespinasse
2013-03-28 20:54 ` Rik van Riel [this message]
2013-03-15 10:54 ` [PATCH v2 07/13] rwsem: use cmpxchg for trying to steal write lock Michel Lespinasse
2013-03-28 16:44 ` Peter Hurley
2013-03-28 20:59 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 08/13] rwsem: avoid taking wait_lock in rwsem_down_write_failed Michel Lespinasse
2013-03-28 21:01 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 09/13] rwsem: skip initial trylock " Michel Lespinasse
2013-03-28 21:16 ` Rik van Riel
2013-03-15 10:54 ` [PATCH v2 10/13] rwsem: simplify __rwsem_do_wake Michel Lespinasse
2013-03-28 16:51 ` Peter Hurley
2013-03-15 10:54 ` [PATCH v2 11/13] rwsem: implement support for write lock stealing on the fastpath Michel Lespinasse
2013-03-28 16:17 ` Peter Hurley
2013-03-15 10:54 ` [PATCH v2 12/13] rwsem: do not block readers at head of queue if other readers are active Michel Lespinasse
2013-03-28 17:25 ` Peter Hurley
2013-03-15 10:54 ` [PATCH v2 13/13] x86 rwsem: avoid taking slow path when stealing write lock Michel Lespinasse
2013-03-28 19:19 ` [PATCH v2 00/13] rwsem fast-path write lock stealing Peter Hurley
[not found] ` <1367097352.1782.14.camel@buesod1.americas.hpqcorp.net>
2013-04-27 23:47 ` Michel Lespinasse
2013-05-07 9:18 ` Michel Lespinasse
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