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

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Message-ID: <20150715064705.GA22609@quack.suse.cz>
Date:	Wed, 15 Jul 2015 08:47:05 +0200
From:	Jan Kara <jack@...e.cz>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, 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 Tue 14-07-15 14:41:13, Dave Hansen wrote:
> 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. :)

Great, thanks for hashing it out. So I'm also in favor of Oleg's approach
as well. We just have to wait until he fixes the outstanding issues with
his code. Dave, just send your fsnotify patch separately to AKPM - he
usually merges fsnotify stuff. Thanks.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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