From: Chris Wright <chrisw@sous-sol.org> To: Nai Xia <nai.xia@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org>, Izik Eidus <izik.eidus@ravellosystems.com>, Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Chris Wright <chrisw@sous-sol.org>, Rik van Riel <riel@redhat.com>, linux-mm <linux-mm@kvack.org>, Johannes Weiner <hannes@cmpxchg.org>, linux-kernel <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 2/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Date: Tue, 21 Jun 2011 15:38:00 -0700 [thread overview] Message-ID: <20110621223800.GO25383@sequoia.sous-sol.org> (raw) In-Reply-To: <201106212136.17445.nai.xia@gmail.com> * 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
WARNING: multiple messages have this Message-ID (diff)
From: Chris Wright <chrisw@sous-sol.org> To: Nai Xia <nai.xia@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org>, Izik Eidus <izik.eidus@ravellosystems.com>, Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Chris Wright <chrisw@sous-sol.org>, Rik van Riel <riel@redhat.com>, linux-mm <linux-mm@kvack.org>, Johannes Weiner <hannes@cmpxchg.org>, linux-kernel <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 2/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Date: Tue, 21 Jun 2011 15:38:00 -0700 [thread overview] Message-ID: <20110621223800.GO25383@sequoia.sous-sol.org> (raw) In-Reply-To: <201106212136.17445.nai.xia@gmail.com> * 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, 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-06-21 22:41 UTC|newest] Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-06-21 12:55 [PATCH 0/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Nai Xia 2011-06-21 12:55 ` Nai Xia 2011-06-21 13:26 ` [PATCH 1/2 " Nai Xia 2011-06-21 13:26 ` Nai Xia 2011-06-21 21:42 ` Chris Wright 2011-06-21 21:42 ` Chris Wright 2011-06-22 0:02 ` Nai Xia 2011-06-22 0:02 ` Nai Xia 2011-06-22 0:42 ` Chris Wright 2011-06-22 0:42 ` Chris Wright 2011-06-21 13:32 ` [PATCH] mmu_notifier, kvm: Introduce dirty bit tracking in spte and mmu notifier to help KSM dirty bit tracking Nai Xia 2011-06-21 13:32 ` Nai Xia 2011-06-22 0:21 ` Chris Wright 2011-06-22 0:21 ` Chris Wright 2011-06-22 4:43 ` Nai Xia 2011-06-22 4:43 ` Nai Xia 2011-06-22 6:15 ` Izik Eidus 2011-06-22 6:15 ` Izik Eidus 2011-06-22 6:38 ` Nai Xia 2011-06-22 6:38 ` Nai Xia 2011-06-22 15:46 ` Chris Wright 2011-06-22 15:46 ` Chris Wright 2011-06-22 10:43 ` Avi Kivity 2011-06-22 10:43 ` Avi Kivity 2011-06-22 11:05 ` Izik Eidus 2011-06-22 11:05 ` Izik Eidus 2011-06-22 11:10 ` Avi Kivity 2011-06-22 11:10 ` Avi Kivity 2011-06-22 11:19 ` Izik Eidus 2011-06-22 11:19 ` Izik Eidus 2011-06-22 11:24 ` Avi Kivity 2011-06-22 11:24 ` Avi Kivity 2011-06-22 11:28 ` Avi Kivity 2011-06-22 11:28 ` Avi Kivity 2011-06-22 11:31 ` Avi Kivity 2011-06-22 11:31 ` Avi Kivity 2011-06-22 11:33 ` Nai Xia 2011-06-22 11:33 ` Nai Xia 2011-06-22 11:39 ` Izik Eidus 2011-06-22 11:39 ` Izik Eidus 2011-06-22 15:39 ` Rik van Riel 2011-06-22 15:39 ` Rik van Riel 2011-06-22 16:55 ` Andrea Arcangeli 2011-06-22 16:55 ` Andrea Arcangeli 2011-06-22 23:37 ` Nai Xia 2011-06-22 23:37 ` Nai Xia 2011-06-22 23:59 ` Andrea Arcangeli 2011-06-22 23:59 ` Andrea Arcangeli 2011-06-23 0:31 ` Nai Xia 2011-06-23 0:31 ` Nai Xia 2011-06-23 0:44 ` Andrea Arcangeli 2011-06-23 0:44 ` Andrea Arcangeli 2011-06-23 1:36 ` Nai Xia 2011-06-23 1:36 ` Nai Xia 2011-06-23 0:00 ` Rik van Riel 2011-06-23 0:00 ` Rik van Riel 2011-06-23 0:42 ` Nai Xia 2011-06-23 0:42 ` Nai Xia 2011-06-22 23:13 ` Nai Xia 2011-06-22 23:13 ` Nai Xia 2011-06-22 23:25 ` Andrea Arcangeli 2011-06-22 23:25 ` Andrea Arcangeli 2011-06-23 1:30 ` Nai Xia 2011-06-23 1:30 ` Nai Xia 2011-06-22 23:28 ` Rik van Riel 2011-06-22 23:28 ` Rik van Riel 2011-06-23 0:52 ` Nai Xia 2011-06-23 0:52 ` Nai Xia 2011-06-22 11:24 ` Nai Xia 2011-06-22 15:03 ` Andrea Arcangeli 2011-06-22 15:03 ` Andrea Arcangeli 2011-06-22 15:19 ` Izik Eidus 2011-06-22 15:19 ` Izik Eidus 2011-06-22 23:19 ` Nai Xia 2011-06-22 23:19 ` Nai Xia 2011-06-22 23:44 ` Andrea Arcangeli 2011-06-22 23:44 ` Andrea Arcangeli 2011-06-23 0:14 ` Nai Xia 2011-06-23 0:14 ` Nai Xia 2011-06-22 23:42 ` Nai Xia 2011-06-22 23:42 ` Nai Xia 2011-06-21 13:36 ` [PATCH 2/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Nai Xia 2011-06-21 13:36 ` Nai Xia 2011-06-21 22:38 ` Chris Wright [this message] 2011-06-21 22:38 ` Chris Wright 2011-06-22 0:04 ` Nai Xia 2011-06-22 0:04 ` Nai Xia 2011-06-22 0:35 ` Chris Wright 2011-06-22 0:35 ` Chris Wright 2011-06-22 4:47 ` Nai Xia 2011-06-22 4:47 ` Nai Xia 2011-06-22 10:55 ` Nai Xia 2011-06-22 10:55 ` Nai Xia 2011-06-22 0:46 ` [PATCH 0/2 " Chris Wright 2011-06-22 0:46 ` Chris Wright 2011-06-22 4:15 ` Nai Xia
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