Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757226Ab1FUWlT (ORCPT ); Tue, 21 Jun 2011 18:41:19 -0400 Received: from sous-sol.org ([216.99.217.87]:51651 "EHLO sequoia.sous-sol.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754991Ab1FUWlS (ORCPT ); Tue, 21 Jun 2011 18:41:18 -0400 Date: Tue, 21 Jun 2011 15:38:00 -0700 From: Chris Wright To: Nai Xia Cc: Andrew Morton , Izik Eidus , Andrea Arcangeli , Hugh Dickins , Chris Wright , Rik van Riel , linux-mm , Johannes Weiner , linux-kernel Subject: Re: [PATCH 2/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Message-ID: <20110621223800.GO25383@sequoia.sous-sol.org> References: <201106212055.25400.nai.xia@gmail.com> <201106212136.17445.nai.xia@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201106212136.17445.nai.xia@gmail.com> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2403 Lines: 63 * 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. > 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. > @@ -454,7 +468,7 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node) > else > ksm_pages_shared--; > put_anon_vma(rmap_item->anon_vma); > - rmap_item->address &= PAGE_MASK; > + rmap_item->address &= ~STABLE_FLAG; > cond_resched(); > } > > @@ -542,7 +556,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) > ksm_pages_shared--; > > put_anon_vma(rmap_item->anon_vma); > - rmap_item->address &= PAGE_MASK; > + rmap_item->address &= ~STABLE_FLAG; > > } else if (rmap_item->address & UNSTABLE_FLAG) { > unsigned char age; > @@ -554,12 +568,14 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) > * than left over from before. > */ > age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); > - BUG_ON(age > 1); > + BUG_ON (age > 1); No need to add space after BUG_ON() there > + > if (!age) > rb_erase(&rmap_item->node, &root_unstable_tree); > > ksm_pages_unshared--; > - rmap_item->address &= PAGE_MASK; > + rmap_item->address &= ~UNSTABLE_FLAG; > + rmap_item->address &= ~SEQNR_MASK; None of these changes are needed AFAICT. &= PAGE_MASK clears all relevant bits. How could it be in a tree, have NEW_FLAG set, and while removing from tree want to preserve NEW_FLAG? 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/