linux-kernel - Re: [PATCH] mm readahead: Fix sys_readahead breakage by reverting 2MB limit (bug 79111)

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Message-ID: <53B5A343.4090402@linux.vnet.ibm.com>
Date:	Fri, 04 Jul 2014 00:08:59 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	David Cohen <david.a.cohen@...ux.intel.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Damien Ramonda <damien.ramonda@...el.com>,
	Jan Kara <jack@...e.cz>, David Rientjes <rientjes@...gle.com>,
	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>,
	linux-mm <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm readahead: Fix sys_readahead breakage by reverting
 2MB limit (bug 79111)

On 07/03/2014 11:59 PM, Linus Torvalds wrote:
> On Thu, Jul 3, 2014 at 11:22 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> So the bugzilla entry worries me a bit - we definitely do not want to
>> regress in case somebody really relied on timing - but without more
>> specific information I still think the real bug is just in the
>> man-page.
>
> Side note: the 2MB limit may be too small. 2M is peanuts on modern
> machines, even for fairly slow IO, and there are lots of files (like
> glibc etc) that people might want to read-ahead during boot. We
> already do bigger read-ahead if people just do "read()" system calls.
> So I could certainly imagine that we should increase it.
>
> I do *not* think we should bow down to insane man-pages that have
> always been wrong, though, and I don't think we should increase it to
> "let's just read-ahead a whole ISO image" kind of sizes..

Okay, how about something like 256MB? I would be happy to send a patch
for that change.

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