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Date: Tue, 24 Feb 2015 17:08:44 -0500
From: Rafael Aquini <aquini@redhat.com>
Subject: Re: [PATCH] mm: readahead: get back a sensible upper limit
Message-ID: <20150224220843.GL19014@t510.redhat.com>
References: <9cc2b63100622f5fd17fa5e4adc59233a2b41877.1424779443.git.aquini@redhat.com>
 <CA+55aFz4D9fS1xt7fg0R9Bnngg+_TbNs3fSAaFwoV7eTeLfP5Q@mail.gmail.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-mm <linux-mm@kvack.org>, Andrew Morton <akpm@linux-foundation.org>, Johannes Weiner <jweiner@redhat.com>, Rik van Riel <riel@redhat.com>, David Rientjes <rientjes@google.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, loberman@redhat.com, Larry Woodman <lwoodman@redhat.com>, Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>

On Tue, Feb 24, 2015 at 01:56:25PM -0800, Linus Torvalds wrote:
> On Tue, Feb 24, 2015 at 4:58 AM, Rafael Aquini <aquini@redhat.com> wrote:
> >
> > This patch brings back the old behavior of max_sane_readahead()
> 
> Yeah no.
> 
> There was a reason that code was killed. No way in hell are we
> bringing back the insanities with node memory etc.
>

Would you consider bringing it back, but instead of node memory state,
utilizing global memory state instead?
 
> Also, we have never actually heard of anything sane that actualyl
> depended on this. Last time this came up it was a made-up benchmark,
> not an actual real load that cared.
> 
> Who can possibly care about this in real life?
> 
People filing bugs complaining their applications that memory map files
are getting hurt by it.

-- Rafael

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