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author | Yuanhan Liu <yuanhan.liu@linux.intel.com> | 2013-02-01 18:59:16 +0800 |
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committer | Ingo Molnar <mingo@kernel.org> | 2013-02-19 08:43:39 +0100 |
commit | 41ef8f826692c8f65882bec0a8211bd4d1d2d19a (patch) | |
tree | a59199669e2ffb6f1fffaaee9a98b50fd82d1d96 /arch | |
parent | fe2b05f7ca9f906be61dced5489f63b8b4d7c770 (diff) | |
download | op-kernel-dev-41ef8f826692c8f65882bec0a8211bd4d1d2d19a.zip op-kernel-dev-41ef8f826692c8f65882bec0a8211bd4d1d2d19a.tar.gz |
rwsem-spinlock: Implement writer lock-stealing for better scalability
We (Linux Kernel Performance project) found a regression
introduced by commit:
5a505085f043 mm/rmap: Convert the struct anon_vma::mutex to an rwsem
which converted all anon_vma::mutex locks rwsem write locks.
The semantics are the same, but the behavioral difference is
quite huge in some cases. After investigating it we found the
root cause: mutexes support lock stealing while rwsems don't.
Here is the link for the detailed regression report:
https://lkml.org/lkml/2013/1/29/84
Ingo suggested adding write lock stealing to rwsems:
"I think we should allow lock-steal between rwsem writers - that
will not hurt fairness as most rwsem fairness concerns relate to
reader vs. writer fairness"
And here is the rwsem-spinlock version.
With this patch, we got a double performance increase in one
test box with following aim7 workfile:
FILESIZE: 1M
POOLSIZE: 10M
10 fork_test
/usr/bin/time output w/o patch /usr/bin/time_output with patch
-- Percent of CPU this job got: 369% Percent of CPU this job got: 537%
Voluntary context switches: 640595016 Voluntary context switches: 157915561
We got a 45% increase in CPU usage and saved about 3/4 voluntary context switches.
Reported-by: LKP project <lkp@linux.intel.com>
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Alex Shi <alex.shi@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Anton Blanchard <anton@samba.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: paul.gortmaker@windriver.com
Link: http://lkml.kernel.org/r/1359716356-23865-1-git-send-email-yuanhan.liu@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
0 files changed, 0 insertions, 0 deletions