From: Davidlohr Bueso <dave@stgolabs.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, akpm@linux-foundation.org, jack@suse.cz,
kirill.shutemov@linux.intel.com, ldufour@linux.vnet.ibm.com,
mhocko@suse.com, mgorman@techsingularity.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 -tip 0/6] locking: Introduce range reader/writer lock
Date: Thu, 20 Apr 2017 10:13:26 -0700 [thread overview]
Message-ID: <20170420171326.GD20746@linux-80c1.suse> (raw)
In-Reply-To: <20170419123735.GB5730@worktop>
On Wed, 19 Apr 2017, Peter Zijlstra wrote:
> - explain why the loss of lock stealing makes sense. IIRC walken added
> that specifically to address mmap_sem performance issues.
That's right, and the same applies to the writer spinning stuff; which
can makes a huge difference - more so than plain stealing. But as I've
mentioned, range locks can improve parallelism, which is/should be much
more welcomed than optimizations to the primitive. So yeah, we loose
in comparing a full range to rwsem (not to mention the xadd stuff).
I have thought of some heuristics for avoiding sleeping under certain
constraints, which could mitigate the spinning step we loose, but
I fear it will never be exactly as fast as rwsems -- just consider
we always take the tree->lock.
Thanks,
Davidlohr
next prev parent reply other threads:[~2017-04-20 17:13 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-06 8:46 [PATCH v2 -tip 0/6] locking: Introduce range reader/writer lock Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 1/6] interval-tree: Build unconditionally Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 2/6] locking: Introduce range reader/writer lock Davidlohr Bueso
2017-04-06 9:01 ` Laurent Dufour
2017-04-06 16:50 ` Davidlohr Bueso
2017-04-13 8:07 ` Laurent Dufour
2017-04-13 8:38 ` Jan Kara
2017-04-13 8:58 ` Laurent Dufour
2017-04-06 10:24 ` Peter Zijlstra
2017-04-18 13:57 ` Laurent Dufour
2017-04-20 16:01 ` Davidlohr Bueso
2017-04-21 7:00 ` Laurent Dufour
2017-04-06 8:46 ` [PATCH 3/6] locking/locktorture: Fix rwsem reader_delay Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 4/6] locking/locktorture: Fix num reader/writer corner cases Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 5/6] locking/locktorture: Support range rwlocks Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 6/6] staging/lustre: Use generic range rwlock Davidlohr Bueso
2017-04-07 10:08 ` Dilger, Andreas
2017-04-07 10:08 ` [lustre-devel] " Dilger, Andreas
2017-04-19 12:37 ` [PATCH v2 -tip 0/6] locking: Introduce range reader/writer lock Peter Zijlstra
2017-04-20 17:13 ` Davidlohr Bueso [this message]
2017-04-20 17:53 ` Peter Zijlstra
2017-04-20 18:36 ` Davidlohr Bueso
2017-04-20 19:10 ` Peter Zijlstra
2017-05-15 9:19 ` Davidlohr Bueso
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