From: Thomas Hellstrom <thellstrom@vmware.com>
To: maarten.lankhosrt@linux.intel.com,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: [PATCH RFC 0/2] locking: Fix ww_mutex algorithm inconsistency.
Date: Fri, 25 May 2018 14:38:53 +0200 [thread overview]
Message-ID: <20180525123855.28956-1-thellstrom@vmware.com> (raw)
The algorithm used for linux Wound/Wait mutexes, is actually not Wound/Wait
but Wait/Die. See for example
http://www.mathcs.emory.edu/~cheung/Courses/554/Syllabus/8-recv+serial/deadlock-compare.html
Rather than renaming them across the tree to something like Wait/Die mutexes or
Deadlock Avoidance mutexes, this patch set implements also the Wound/Wait
algorithm It shouldn't touch the binary ordinary mutex paths when compiled
with otpimization.
We use Wound/Wait for the modeset locks which in theory may benefit slightly
from Wound/Wait rather than Wait/Die, but Wait/Die is actually superior for
larger number of simultaneous contending transactions so we keep the original
implementation as a choice, and don't touch the algorithm used by the
reservation objects.
Performance- and functional testing has been done using
git://people.freedesktop.org/~thomash/ww_mutex_test
Using WW_BUILTIN and 4 and 16 competing threads.
Another option is of course to ignore the the naming / algorithm inconsistency.
next reply other threads:[~2018-05-25 12:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-25 12:38 Thomas Hellstrom [this message]
2018-05-25 12:38 ` [PATCH RFC 1/2] locking: Implement an algorithm choice for Wound-Wait mutexes Thomas Hellstrom
2018-05-25 12:38 ` [PATCH RFC 2/2] drm: Change deadlock-avoidance algorithm for the modeset locks Thomas Hellstrom
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