Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752003Ab1FVEsC (ORCPT ); Wed, 22 Jun 2011 00:48:02 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:44964 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751102Ab1FVEsB (ORCPT ); Wed, 22 Jun 2011 00:48:01 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:reply-to:to:subject:date:user-agent:cc:references:in-reply-to :mime-version:content-type:content-transfer-encoding:message-id; b=gTX588wWP96QhExKg62akp8/m37T/QMf0LbkYK3Gcir/vLWr8Z9P7Yd5XujbrQYpug EfBl3Zdg/Or4pvTY0oaeoo0Y/QPYkt8iTrht8tLu561V/SIVeIpGUKu92CWlkjYM9OZx zTyuULMN1TlxzaiInQ9d1EGH+6Mf7R6y8H8rs= From: Nai Xia Reply-To: nai.xia@gmail.com To: Chris Wright Subject: Re: [PATCH 2/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Date: Wed, 22 Jun 2011 12:47:39 +0800 User-Agent: KMail/1.13.5 (Linux/2.6.39; KDE/4.5.5; i686; ; ) Cc: Andrew Morton , Izik Eidus , Andrea Arcangeli , Hugh Dickins , Rik van Riel , "linux-mm" , Johannes Weiner , "linux-kernel" References: <201106212055.25400.nai.xia@gmail.com> <201106220804.12508.nai.xia@gmail.com> <20110622003536.GQ25383@sequoia.sous-sol.org> In-Reply-To: <20110622003536.GQ25383@sequoia.sous-sol.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <201106221247.39827.nai.xia@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2318 Lines: 61 On Wednesday 22 June 2011 08:35:36 Chris Wright wrote: > * Nai Xia (nai.xia@gmail.com) wrote: > > (Sorry for repeated mail, I forgot to Cc the list..) > > > > On Wednesday 22 June 2011 06:38:00 you wrote: > > > * Nai Xia (nai.xia@gmail.com) wrote: > > > > Introduced ksm_page_changed() to reference the dirty bit of a pte. We clear > > > > the dirty bit for each pte scanned but don't flush the tlb. For a huge page, > > > > if one of the subpage has changed, we try to skip the whole huge page > > > > assuming(this is true by now) that ksmd linearly scans the address space. > > > > > > This doesn't build w/ kvm as a module. > > > > I think it's because of the name-error of a related kvm patch, which I only sent > > in a same email thread. http://marc.info/?l=linux-mm&m=130866318804277&w=2 > > The patch split is not clean...I'll redo it. > > > > It needs an export as it is. > ERROR: "kvm_dirty_update" [arch/x86/kvm/kvm-intel.ko] undefined! Oops, yes, I forgot to do that! I'll correct it in the next submission. Thanks, Nai > > Although perhaps could be done w/out that dirty_update altogether (as I > mentioned in other email)? > > > > > > > > A NEW_FLAG is also introduced as a status of rmap_item to make ksmd scan > > > > more aggressively for new VMAs - only skip the pages considered to be volatile > > > > by the dirty bits. This can be enabled/disabled through KSM's sysfs interface. > > > > > > This seems like it should be separated out. And while it might be useful > > > to enable/disable for testing, I don't think it's worth supporting for > > > the long term. Would also be useful to see the value of this flag. > > > > I think it maybe useful for uses who want to turn on/off this scan policy explicitly > > according to their working sets? > > Can you split it out, and show the benefit of it directly? I think it > only benefits: > > p = mmap() > memset(p, $value, entire buffer); > ... > very slowly (w.r.t scan times) touch bits of buffer and trigger cow to > break sharing. > > Would you agree? > > thanks, > -chris > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/