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Date: Fri, 16 Oct 2009 09:04:46 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Hugh Dickins <hugh.dickins@...cali.co.uk> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH 8/9] swap_info: note SWAP_MAP_SHMEM On Thu, 15 Oct 2009 23:23:24 +0100 (BST) Hugh Dickins <hugh.dickins@...cali.co.uk> wrote: > On Thu, 15 Oct 2009, KAMEZAWA Hiroyuki wrote: > > On Thu, 15 Oct 2009 01:57:28 +0100 (BST) > > Hugh Dickins <hugh.dickins@...cali.co.uk> wrote: > > > > > While we're fiddling with the swap_map values, let's assign a particular > > > value to shmem/tmpfs swap pages: their swap counts are never incremented, > > > and it helps swapoff's try_to_unuse() a little if it can immediately > > > distinguish those pages from process pages. > > > > > > Since we've no use for SWAP_MAP_BAD | COUNT_CONTINUED, > > > we might as well use that 0xbf value for SWAP_MAP_SHMEM. > > > > > > Signed-off-by: Hugh Dickins <hugh.dickins@...cali.co.uk> > > > > I welcome this! > > Ah, I did wonder whether you might find some memcg use for it too: > I'm guessing your welcome means that you do have some such in mind. > yes, I'm thinking I can use this or not on memcg for simplifying memcg's hooks for shmem. It's complicated ;) I have to test memcg+shmem carefully again after this patch but I think there will be no trouble, now. > (By the way, there's no particular need to use that 0xbf value: > during most of my testing I was using SWAP_MAP_SHMEM 0x3e and > SWAP_MAP_MAX 0x3d; but then noticed that 0xbf just happened to be > free, and also happened to sail through the tests in the right way. > But if it ever becomes a nuisance there, no problem to move it.) > Hmm. I myself have no troubles whatever free vaule is used. let me clarify.. xx00 0000 xx11 1110 - swap count max 01xx xxxx - swap has cache 1xxx xxxx - swap count has continuation 1x11 1111 - swap for shmem seems not very bad. Regards, -Kame -- 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/
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