linux-kernel - Re: [PATCH v2] Make VM_MAX_READAHEAD a kernel parameter

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Message-ID: <4B823D70.80800@linux.vnet.ibm.com>
Date:	Mon, 22 Feb 2010 09:16:48 +0100
From:	Christian Ehrhardt <ehrhardt@...ux.vnet.ibm.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
CC:	Nikanth Karthikesan <knikanth@...e.de>,
	Dave Chinner <david@...morbit.com>,
	Ankit Jain <radical@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v2] Make VM_MAX_READAHEAD a kernel parameter



Wu Fengguang wrote:
> Nikanth,
> 
>> I didn't want to impose artificial restrictions. I think Wu's patch set would 
>> be adding some restrictions, like minimum readahead. He could fix it when he 
>> modifies the patch to include in his patch set.
> 
> OK, I imposed a larger bound -- 128MB.
> And values 1-4095 (more exactly: PAGE_CACHE_SIZE) are prohibited mainly to 
> catch "readahead=128" where the user really means to do 128 _KB_ readahead.
> 
> Christian, with this patch and more patches to scale down readahead
> size on small memory/device size, I guess it's no longer necessary to
> introduce a CONFIG_READAHEAD_SIZE?

Yes as I mentioned before a kernel parameter supersedes a config symbol 
in my opinion too.
-> agreed

> Thanks,
> Fengguang
> ---

-- 

Grüsse / regards, Christian Ehrhardt
IBM Linux Technology Center, System z Linux Performance
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