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Message-ID: <Pine.LNX.4.64.0910160314310.2993@sister.anvils> Date: Fri, 16 Oct 2009 03:24:57 +0100 (BST) From: Hugh Dickins <hugh.dickins@...cali.co.uk> To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> cc: Andrew Morton <akpm@...ux-foundation.org>, Nitin Gupta <ngupta@...are.org>, hongshin@...il.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH 7/9] swap_info: swap count continuations On Fri, 16 Oct 2009, KAMEZAWA Hiroyuki wrote: > > > My concern is that small numbers of swap_map[] which has too much refcnt > can consume too much pages. > > If an entry is shared by 65535, 65535/128 = 512 page will be used. > (I'm sorry if I don't undestand implementation correctly.) Ah, you're thinking it's additive: perhaps because I use the name "continuation", which may give that impression - maybe there's a better name I can give it. No, it's multiplicative - just like 999 is almost a thousand, not 27. If an entry is shared by 65535, then it needs its original swap_map page (0 to 0x3e) and a continuation page (0 to 0x7f) and another continuation page (0 to 0x7f): if I've got my arithmetic right, those three pages can hold a shared count up to 1032191, for every one of that group of PAGE_SIZE neighbouring pages. Hugh -- 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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