From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikita Danilov MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16404.63446.649110.348477@laputa.namesys.com> Date: Mon, 26 Jan 2004 14:19:50 +0300 Subject: Re: [BENCHMARKS] Namesys VM patches improve kbuild In-Reply-To: <4011C537.8040104@cyberone.com.au> References: <400F630F.80205@cyberone.com.au> <20040121223608.1ea30097.akpm@osdl.org> <16399.42863.159456.646624@laputa.namesys.com> <40105633.4000800@cyberone.com.au> <16400.63379.453282.283117@laputa.namesys.com> <4011392D.1090600@cyberone.com.au> <16401.16474.881069.437933@laputa.namesys.com> <4011C537.8040104@cyberone.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andrew Morton , linux-mm@kvack.org List-ID: Nick Piggin writes: > [...] > > But by clearing the referenced bit when below the reclaim_mapped > threshold, you're throwing this information away. > > Say you have 16 mapped pages on the active list, 8 referenced, 8 not. > You do a !reclaim_mapped scan. Your 16 pages are now in the same > order and none are referenced. You now do a reclaim_mapped scan and > reclaim 8 pages. 4 of them were the referenced ones, 4 were not. > > With my change, you would reclaim all 8 non referenced pages. Which is wrong, because none of them was referenced _recently_. These pages are cold, according to the VM's notion of hotness. (Long time probably has passed between !reclaim_mapped and reclaim_mapped scans in your example.) It seems correct to make deactivation decision on the basic of recent accesses to the page rather than by checking whether page was ever accessed. > Nikita. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org