linux-kernel - Re: [PATCH RFC 0/4] change sb_writers to use percpu_rw

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Message-ID: <55A581F9.3090507@linux.intel.com>
Date:	Tue, 14 Jul 2015 14:41:13 -0700
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Jan Kara <jack@...e.cz>, Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Daniel Wagner <daniel.wagner@...-carit.de>,
	Davidlohr Bueso <dave@...olabs.net>,
	Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 0/4] change sb_writers to use percpu_rw_semaphore

On 07/14/2015 02:22 PM, Oleg Nesterov wrote:
>> Using my little write-1-byte test (under will-it-scale), your 4 patches
>> improves the number of writes/sec by 12%.  My 3 patches improve the
>> number of writes/sec by 32%.

I looked at it again.  I tested with this patch in addition to the ones
modifying __sb_start/end_write():

	https://lkml.org/lkml/2015/6/24/682

That is where the performance delta came from.  Your patches (plus the
fsnotify optimization) perform very similarly to my approach.

Yours remove so much code that I think they are the preferable approach.

They don't compile with lockdep on, btw. :)
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