Message-ID: <494292D4.6090302@redhat.com>
Date: Fri, 12 Dec 2008 11:35:32 -0500
From: Rik van Riel <riel@redhat.com>
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To: Hugh Dickins <hugh@veritas.com>
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Jens Axboe <jens.axboe@oracle.com>, Jean Delvare <khali@linux-fr.org>,
       Trond Myklebust <Trond.Myklebust@netapp.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] block: Fix LSF default inconsistency
References: <20081211202923.330F.KOSAKI.MOTOHIRO@jp.fujitsu.com>  <20081211113646.GI23742@kernel.dk>  <20081211204006.3312.KOSAKI.MOTOHIRO@jp.fujitsu.com>  <20081212075844.GH23742@kernel.dk> <49426C16.6040108@redhat.com> <2f11576a0812120711l130e07c3x94ff3b1e64959edf@mail.gmail.com> <Pine.LNX.4.64.0812121559220.19722@blonde.anvils>
In-Reply-To: <Pine.LNX.4.64.0812121559220.19722@blonde.anvils>
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Hugh Dickins wrote:
> On Sat, 13 Dec 2008, KOSAKI Motohiro wrote:
>   
>> To move mlocked file cache page to unevictable list is useful although
>> swapless embedded device.
>>     
>
> Yes, I don't understand why Rik suggested CONFIG_SWAP for it either.
On swapless systems (with CONFIG_SWAP=n), we never scan
the anon lists, so we do not need to split out the mlocked pages from
the anon pages.

On a system with swap, we want to split out the mlocked pages
so that scan balancing always works right.  So whenever
CONFIG_SWAP is on, we want CONFIG_UNEVICTABLE_LRU
to be on as well.

That means we can replace CONFIG_UNEVICTABLE_LRU
with CONFIG_SWAP throughout the code, and get a kernel
with the desired behaviour either way.


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