linux-kernel - Re: [PATCH 2/8] readahead: make default readahead size a kernel parameter

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 24 Nov 2011 23:28:22 +0100
From:	Jan Kara <jack@...e.cz>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Ankit Jain <radical@...il.com>,
	Dave Chinner <david@...morbit.com>,
	Christian Ehrhardt <ehrhardt@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Nikanth Karthikesan <knikanth@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 2/8] readahead: make default readahead size a kernel
 parameter

On Mon 21-11-11 19:35:40, Wu Fengguang wrote:
> On Mon, Nov 21, 2011 at 06:01:37PM +0800, Christoph Hellwig wrote:
> > On Mon, Nov 21, 2011 at 05:18:21PM +0800, Wu Fengguang wrote:
> > > From: Nikanth Karthikesan <knikanth@...e.de>
> > > 
> > > Add new kernel parameter "readahead=", which allows user to override
> > > the static VM_MAX_READAHEAD=128kb.
> > 
> > Is a boot-time paramter really such a good idea?  I would at least
> 
> It's most convenient to set at boot time, because the default size
> will be used to initialize all the block devices.
> 
> > make it a sysctl so that it's run-time controllable, including
> > beeing able to set it from initscripts.
> 
> Once boot up, it's more natural to set the size one by one, for
> example
> 
>         blockdev --setra 1024 /dev/sda2
> or
>         echo 512 > /sys/block/sda/queue/read_ahead_kb
> 
> And you still have the chance to modify the global default, but the
> change will only be inherited by newly created devices thereafter:
> 
>         echo 512 > /sys/devices/virtual/bdi/default/read_ahead_kb
> 
> The above command is very suitable for use in initscripts.  However
> there are no natural way to do sysctl as there is no such a global
> value.
  Well, you can always have an udev rule to set read_ahead_kb to whatever
you want. In some respect that looks like a nicer solution to me...

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/