linux-kernel - Re: [PATCH] gfs2: use __vmalloc GFP

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Message-ID: <20150205114459.GI12722@dastard>
Date:	Thu, 5 Feb 2015 22:45:00 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Oleg Drokin <green@...uxhacker.ru>
Cc:	Steven Whitehouse <swhiteho@...hat.com>, cluster-devel@...hat.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org
Subject: Re: [PATCH] gfs2: use __vmalloc GFP_NOFS for fs-related allocations.

On Wed, Feb 04, 2015 at 02:13:29AM -0500, Oleg Drokin wrote:
> Hello!
> 
> On Feb 3, 2015, at 5:33 PM, Dave Chinner wrote:
> >> I also wonder if vmalloc is still very slow? That was the case some
> >> time ago when I noticed a problem in directory access times in gfs2,
> >> which made us change to use kmalloc with a vmalloc fallback in the
> >> first place,
> > Another of the "myths" about vmalloc. The speed and scalability of
> > vmap/vmalloc is a long solved problem - Nick Piggin fixed the worst
> > of those problems 5-6 years ago - see the rewrite from 2008 that
> > started with commit db64fe0 ("mm: rewrite vmap layer")....
> 
> This actually might be less true than one would hope. At least somewhat
> recent studies by LLNL (https://jira.hpdd.intel.com/browse/LU-4008)
> show that there's huge contention on vmlist_lock, so if you have vmalloc

vmlist_lock and the list it protected went away in 3.10.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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