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Message-ID: <20111108085952.GA15142@barrios-laptop.redhat.com>
Date: Tue, 8 Nov 2011 17:59:52 +0900
From: Minchan Kim <minchan.kim@...il.com>
To: Shaohua Li <shaohua.li@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"aarcange@...hat.com" <aarcange@...hat.com>,
Hugh Dickins <hughd@...gle.com>,
Rik van Riel <riel@...hat.com>, mel <mel@....ul.ie>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
linux-mm <linux-mm@...ck.org>,
lkml <linux-kernel@...r.kernel.org>
Subject: Re: [patch 5/5]thp: split huge page if head page is isolated
On Wed, Nov 02, 2011 at 11:17:55AM +0800, Shaohua Li wrote:
> On Mon, 2011-10-31 at 17:03 +0800, Shaohua Li wrote:
> > On Mon, 2011-10-31 at 16:23 +0800, Minchan Kim wrote:
> > > On Mon, Oct 31, 2011 at 09:21:28AM +0800, Shaohua Li wrote:
> > > > On Sat, 2011-10-29 at 08:06 +0800, Minchan Kim wrote:
> > > > > On Tue, Oct 25, 2011 at 10:59:40AM +0800, Shaohua Li wrote:
> > > > > > With current logic, if page reclaim finds a huge page, it will just reclaim
> > > > > > the head page and leave tail pages reclaimed later. Let's take an example,
> > > > > > lru list has page A and B, page A is huge page:
> > > > > > 1. page A is isolated
> > > > > > 2. page B is isolated
> > > > > > 3. shrink_page_list() adds page A to swap page cache. so page A is split.
> > > > > > page A+1, page A+2, ... are added to lru list.
> > > > > > 4. shrink_page_list() adds page B to swap page cache.
> > > > > > 5. page A and B is written out and reclaimed.
> > > > > > 6. page A+1, A+2 ... is isolated and reclaimed later.
> > > > > > So the reclaim order is A, B, ...(maybe other pages), A+1, A+2 ...
> > > > > >
> > > > > > We expected the whole huge page A is reclaimed in the meantime, so
> > > > > > the order is A, A+1, ... A+HPAGE_PMD_NR-1, B, ....
> > > > > >
> > > > > > With this patch, we do huge page split just after the head page is isolated
> > > > > > for inactive lru list, so the tail pages will be reclaimed immediately.
> > > > > >
> > > > > > In a test, a range of anonymous memory is written and will trigger swap.
> > > > > > Without the patch:
> > > > > > #cat /proc/vmstat|grep thp
> > > > > > thp_fault_alloc 451
> > > > > > thp_fault_fallback 0
> > > > > > thp_collapse_alloc 0
> > > > > > thp_collapse_alloc_failed 0
> > > > > > thp_split 238
> > > > > >
> > > > > > With the patch:
> > > > > > #cat /proc/vmstat|grep thp
> > > > > > thp_fault_alloc 450
> > > > > > thp_fault_fallback 1
> > > > > > thp_collapse_alloc 0
> > > > > > thp_collapse_alloc_failed 0
> > > > > > thp_split 103
> > > > > >
> > > > > > So the thp_split number is reduced a lot, though there is one extra
> > > > > > thp_fault_fallback.
> > > > > >
> > > > > > Signed-off-by: Shaohua Li <shaohua.li@...el.com>
> > > > > > ---
> > > > > > include/linux/memcontrol.h | 3 +-
> > > > > > mm/memcontrol.c | 12 +++++++++--
> > > > > > mm/vmscan.c | 49 ++++++++++++++++++++++++++++++++++-----------
> > > > > > 3 files changed, 50 insertions(+), 14 deletions(-)
> > > > > >
> > > > > > Index: linux/mm/vmscan.c
> > > > > > ===================================================================
> > > > > > --- linux.orig/mm/vmscan.c 2011-10-25 08:36:08.000000000 +0800
> > > > > > +++ linux/mm/vmscan.c 2011-10-25 09:51:44.000000000 +0800
> > > > > > @@ -1076,7 +1076,8 @@ int __isolate_lru_page(struct page *page
> > > > > > */
> > > > > > static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> > > > > > struct list_head *src, struct list_head *dst,
> > > > > > - unsigned long *scanned, int order, int mode, int file)
> > > > > > + unsigned long *scanned, int order, int mode, int file,
> > > > > > + struct page **split_page)
> > > > > > {
> > > > > > unsigned long nr_taken = 0;
> > > > > > unsigned long nr_lumpy_taken = 0;
> > > > > > @@ -1100,7 +1101,12 @@ static unsigned long isolate_lru_pages(u
> > > > > > case 0:
> > > > > > list_move(&page->lru, dst);
> > > > > > mem_cgroup_del_lru(page);
> > > > > > - nr_taken += hpage_nr_pages(page);
> > > > > > + if (PageTransHuge(page) && split_page) {
> > > > > > + nr_taken++;
> > > > > > + *split_page = page;
> > > > > > + goto out;
> > > > > > + } else
> > > > > > + nr_taken += hpage_nr_pages(page);
> > > > > > break;
> > > > > >
> > > > > > case -EBUSY:
> > > > > > @@ -1158,11 +1164,16 @@ static unsigned long isolate_lru_pages(u
> > > > > > if (__isolate_lru_page(cursor_page, mode, file) == 0) {
> > > > > > list_move(&cursor_page->lru, dst);
> > > > > > mem_cgroup_del_lru(cursor_page);
> > > > > > - nr_taken += hpage_nr_pages(page);
> > > > > > nr_lumpy_taken++;
> > > > > > if (PageDirty(cursor_page))
> > > > > > nr_lumpy_dirty++;
> > > > > > scan++;
> > > > > > + if (PageTransHuge(page) && split_page) {
> > > > > > + nr_taken++;
> > > > > > + *split_page = page;
> > > > > > + goto out;
> > > > > > + } else
> > > > > > + nr_taken += hpage_nr_pages(page);
> > > > > > } else {
> > > > > > /*
> > > > > > * Check if the page is freed already.
> > > > > > @@ -1188,6 +1199,7 @@ static unsigned long isolate_lru_pages(u
> > > > > > nr_lumpy_failed++;
> > > > > > }
> > > > > >
> > > > > > +out:
> > > > > > *scanned = scan;
> > > > > >
> > > > > > trace_mm_vmscan_lru_isolate(order,
> > > > > > @@ -1202,7 +1214,8 @@ static unsigned long isolate_pages_globa
> > > > > > struct list_head *dst,
> > > > > > unsigned long *scanned, int order,
> > > > > > int mode, struct zone *z,
> > > > > > - int active, int file)
> > > > > > + int active, int file,
> > > > > > + struct page **split_page)
> > > > > > {
> > > > > > int lru = LRU_BASE;
> > > > > > if (active)
> > > > > > @@ -1210,7 +1223,7 @@ static unsigned long isolate_pages_globa
> > > > > > if (file)
> > > > > > lru += LRU_FILE;
> > > > > > return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
> > > > > > - mode, file);
> > > > > > + mode, file, split_page);
> > > > > > }
> > > > > >
> > > > > > /*
> > > > > > @@ -1444,10 +1457,12 @@ shrink_inactive_list(unsigned long nr_to
> > > > > > {
> > > > > > LIST_HEAD(page_list);
> > > > > > unsigned long nr_scanned;
> > > > > > + unsigned long total_scanned = 0;
> > > > > > unsigned long nr_reclaimed = 0;
> > > > > > unsigned long nr_taken;
> > > > > > unsigned long nr_anon;
> > > > > > unsigned long nr_file;
> > > > > > + struct page *split_page;
> > > > > >
> > > > > > while (unlikely(too_many_isolated(zone, file, sc))) {
> > > > > > congestion_wait(BLK_RW_ASYNC, HZ/10);
> > > > > > @@ -1458,16 +1473,19 @@ shrink_inactive_list(unsigned long nr_to
> > > > > > }
> > > > > >
> > > > > > set_reclaim_mode(priority, sc, false);
> > > > > > +again:
> > > > > > lru_add_drain();
> > > > > > + split_page = NULL;
> > > > > > spin_lock_irq(&zone->lru_lock);
> > > > > >
> > > > > > if (scanning_global_lru(sc)) {
> > > > > > - nr_taken = isolate_pages_global(nr_to_scan,
> > > > > > + nr_taken = isolate_pages_global(nr_to_scan - total_scanned,
> > > > > > &page_list, &nr_scanned, sc->order,
> > > > > > sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
> > > > > > ISOLATE_BOTH : ISOLATE_INACTIVE,
> > > > > > - zone, 0, file);
> > > > > > + zone, 0, file, &split_page);
> > > > > > zone->pages_scanned += nr_scanned;
> > > > > > + total_scanned += nr_scanned;
> > > > > > if (current_is_kswapd())
> > > > > > __count_zone_vm_events(PGSCAN_KSWAPD, zone,
> > > > > > nr_scanned);
> > > > > > @@ -1475,12 +1493,13 @@ shrink_inactive_list(unsigned long nr_to
> > > > > > __count_zone_vm_events(PGSCAN_DIRECT, zone,
> > > > > > nr_scanned);
> > > > > > } else {
> > > > > > - nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
> > > > > > + nr_taken = mem_cgroup_isolate_pages(nr_to_scan - total_scanned,
> > > > > > &page_list, &nr_scanned, sc->order,
> > > > > > sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
> > > > > > ISOLATE_BOTH : ISOLATE_INACTIVE,
> > > > > > zone, sc->mem_cgroup,
> > > > > > - 0, file);
> > > > > > + 0, file, &split_page);
> > > > > > + total_scanned += nr_scanned;
> > > > > > /*
> > > > > > * mem_cgroup_isolate_pages() keeps track of
> > > > > > * scanned pages on its own.
> > > > > > @@ -1491,11 +1510,19 @@ shrink_inactive_list(unsigned long nr_to
> > > > > > spin_unlock_irq(&zone->lru_lock);
> > > > > > return 0;
> > > > > > }
> > > > > > + if (split_page && total_scanned < nr_to_scan) {
> > > > > > + spin_unlock_irq(&zone->lru_lock);
> > > > > > + split_huge_page(split_page);
> > > > > > + goto again;
> > > > > > + }
> > > > > >
> > > > > > update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
> > > > > >
> > > > > > spin_unlock_irq(&zone->lru_lock);
> > > > > >
> > > > > > + if (split_page)
> > > > > > + split_huge_page(split_page);
> > > > > > +
> > > > > > nr_reclaimed = shrink_page_list(&page_list, zone, sc);
> > > > > >
> > > > > > /* Check if we should syncronously wait for writeback */
> > > > > > @@ -1589,13 +1616,13 @@ static void shrink_active_list(unsigned
> > > > > > nr_taken = isolate_pages_global(nr_pages, &l_hold,
> > > > > > &pgscanned, sc->order,
> > > > > > ISOLATE_ACTIVE, zone,
> > > > > > - 1, file);
> > > > > > + 1, file, NULL);
> > > > > > zone->pages_scanned += pgscanned;
> > > > > > } else {
> > > > > > nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
> > > > > > &pgscanned, sc->order,
> > > > > > ISOLATE_ACTIVE, zone,
> > > > > > - sc->mem_cgroup, 1, file);
> > > > > > + sc->mem_cgroup, 1, file, NULL);
> > > > > > /*
> > > > > > * mem_cgroup_isolate_pages() keeps track of
> > > > > > * scanned pages on its own.
> > > > > > Index: linux/mm/memcontrol.c
> > > > > > ===================================================================
> > > > > > --- linux.orig/mm/memcontrol.c 2011-10-25 08:36:08.000000000 +0800
> > > > > > +++ linux/mm/memcontrol.c 2011-10-25 09:33:51.000000000 +0800
> > > > > > @@ -1187,7 +1187,8 @@ unsigned long mem_cgroup_isolate_pages(u
> > > > > > unsigned long *scanned, int order,
> > > > > > int mode, struct zone *z,
> > > > > > struct mem_cgroup *mem_cont,
> > > > > > - int active, int file)
> > > > > > + int active, int file,
> > > > > > + struct page **split_page)
> > > > > > {
> > > > > > unsigned long nr_taken = 0;
> > > > > > struct page *page;
> > > > > > @@ -1224,7 +1225,13 @@ unsigned long mem_cgroup_isolate_pages(u
> > > > > > case 0:
> > > > > > list_move(&page->lru, dst);
> > > > > > mem_cgroup_del_lru(page);
> > > > > > - nr_taken += hpage_nr_pages(page);
> > > > > > + if (PageTransHuge(page) && split_page) {
> > > > > > + nr_taken++;
> > > > > > + *split_page = page;
> > > > > > + goto out;
> > > > > > + } else
> > > > > > + nr_taken += hpage_nr_pages(page);
> > > > > > +
> > > > > > break;
> > > > > > case -EBUSY:
> > > > > > /* we don't affect global LRU but rotate in our LRU */
> > > > > > @@ -1235,6 +1242,7 @@ unsigned long mem_cgroup_isolate_pages(u
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > +out:
> > > > > > *scanned = scan;
> > > > > >
> > > > > > trace_mm_vmscan_memcg_isolate(0, nr_to_scan, scan, nr_taken,
> > > > > > Index: linux/include/linux/memcontrol.h
> > > > > > ===================================================================
> > > > > > --- linux.orig/include/linux/memcontrol.h 2011-10-25 08:36:08.000000000 +0800
> > > > > > +++ linux/include/linux/memcontrol.h 2011-10-25 09:33:51.000000000 +0800
> > > > > > @@ -37,7 +37,8 @@ extern unsigned long mem_cgroup_isolate_
> > > > > > unsigned long *scanned, int order,
> > > > > > int mode, struct zone *z,
> > > > > > struct mem_cgroup *mem_cont,
> > > > > > - int active, int file);
> > > > > > + int active, int file,
> > > > > > + struct page **split_page);
> > > > > >
> > > > > > #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > > > > > /*
> > > > > >
> > > > > >
> > > > >
> > > > > I saw the code. my concern is your patch could make unnecessary split of THP.
> > > > >
> > > > > When we isolates page, we can't know whether it's working set or not.
> > > > > So split should happen after we judge it's working set page.
> > > > yes, but since memory is big currently, it's unlikely the isolated page
> > > > get accessed in the window. And I only did the split in
> > >
> > > We don't check page_reference when isolate happens.
> > > Window which between isolation time and reclaim?
> > > No. Window is from inactive's head to tail and it's the basic concept of
> > > our LRU.
> > >
> > > > shrink_inactive_list, not in active list.
> > >
> > > But inactive list's size could be still big and
> > > page reference heuristic is very important for reclaim algorithm.
> > I mean pages aren't referenced. but ok, I can't take such assumption.
> >
> > > > And THP has mechanism to collapse small pages to huge page later.
> > >
> > > You mean "merge" instead of "collapse"?
> > >
> > > >
> > > > > If you really want to merge this patch, I suggest that
> > > > > we can handle it in shrink_page_list step, not isolation step.
> > > > >
> > > > > My totally untested code which is just to show the concept is as follows,
> > > > I did consider this option before. It has its problem too. The isolation
> > > > can isolate several huge page one time. And then later shrink_page_list
> > > > can swap several huge page one time, which is unfortunate. I'm pretty
> > > > sure this method can't reduce the thp_split count in my test. It could
> > >
> > > I understand your point but approach isn't good to me.
> > > Maybe we can check whether we are going on or not before other THP page split happens
> > > in shrink_page_list. If we split THP page successfully, maybe we can skip another THP split.
> > > Another idea is we can avoid split of THP unless high order reclaim happens or low order
> > > high priority pressure happens.
> > I agreed the split better be done at shrink_page_list, but we must avoid
> > isolate too many pages. I'll check if I can have a better solution for
> > next post.
> Let me try again.
>
> Subject: thp: improve huge page reclaim -v2
>
> With transparent huge page enabled, huge page will be split if it will
> be reclaimed. With current logic, if page reclaim finds a huge page,
> it will just reclaim the head page and leave tail pages reclaimed later.
> Let's take an example, lru list has page A and B, page A is huge page:
> 1. page A is isolated
> 2. page B is isolated
> 3. shrink_page_list() adds page A to swap page cache. so page A is split.
> page A+1, page A+2, ... are added to lru list.
> 4. shrink_page_list() adds page B to swap page cache.
> 5. page A and B is written out and reclaimed.
> 6. page A+1, A+2 ... is isolated and reclaimed later.
> So the reclaim order is A, B, ...(maybe other pages), A+1, A+2 ...
> The worst case could be we isolate/split 32 huge pages to try to reclaim
> a huge page, but we only the 32 head pages are reclaimed.
>
> We expected the whole huge page A is reclaimed in the meantime, so
> the order is A, A+1, ... A+HPAGE_PMD_NR-1, B, .... This could reduce a lot
> of unnecessary huge page split and improve the reclaim.
>
> With this patch, if a huge page is found in isolation, don't continue
> isolation. Since if the huge page is reclaimed, we can reclaim more pages
> than SWAP_CLUSTER_MAX. In shrink_page_list(), the huge page is split and
> all tail pages will be added to the isolation list, so the tail pages can
> be reclaimed immediately.
>
> The drawback is we might isolate less pages if a huge page is found. But
> I thought the benefit is far more than the drawback.
>
> All code path are with PageTransHuge(), so should have no impact to normal
> cases.
>
> In a test, a range of anonymous memory is written and will trigger swap.
> Without the patch:
> #cat /proc/vmstat|grep thp
> thp_fault_alloc 451
> thp_fault_fallback 0
> thp_collapse_alloc 0
> thp_collapse_alloc_failed 0
> thp_split 238
>
> With the patch:
> #cat /proc/vmstat|grep thp
> thp_fault_alloc 451
> thp_fault_fallback 0
> thp_collapse_alloc 0
> thp_collapse_alloc_failed 0
> thp_split 76
>
> So the thp_split number is reduced a lot.
>
> v1->v2: Do the huge page split in shrink_page_list(). Some code are adopted from
> Minchan's.
>
> Signed-off-by: Shaohua Li <shaohua.li@...el.com>
>
> ---
> include/linux/huge_mm.h | 7 ++++++-
> include/linux/memcontrol.h | 3 ++-
> include/linux/swap.h | 3 ++-
> mm/huge_memory.c | 14 ++++++++------
> mm/memcontrol.c | 6 +++++-
> mm/swap.c | 10 +++++++++-
> mm/swap_state.c | 6 ------
> mm/vmscan.c | 27 ++++++++++++++++++++-------
> 8 files changed, 52 insertions(+), 24 deletions(-)
>
> Index: linux/include/linux/huge_mm.h
> ===================================================================
> --- linux.orig/include/linux/huge_mm.h 2011-11-02 09:48:16.000000000 +0800
> +++ linux/include/linux/huge_mm.h 2011-11-02 10:06:33.000000000 +0800
> @@ -81,7 +81,12 @@ extern int copy_pte_range(struct mm_stru
> extern int handle_pte_fault(struct mm_struct *mm,
> struct vm_area_struct *vma, unsigned long address,
> pte_t *pte, pmd_t *pmd, unsigned int flags);
> -extern int split_huge_page(struct page *page);
> +extern int split_huge_page_list(struct page *page, struct list_head *dst);
> +static inline int split_huge_page(struct page *page)
> +{
> + return split_huge_page_list(page, NULL);
> +}
> +
> extern void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd);
> #define split_huge_page_pmd(__mm, __pmd) \
> do { \
> Index: linux/include/linux/swap.h
> ===================================================================
> --- linux.orig/include/linux/swap.h 2011-11-02 09:48:16.000000000 +0800
> +++ linux/include/linux/swap.h 2011-11-02 10:06:33.000000000 +0800
> @@ -218,7 +218,8 @@ extern unsigned int nr_free_pagecache_pa
> extern void __lru_cache_add(struct page *, enum lru_list lru);
> extern void lru_cache_add_lru(struct page *, enum lru_list lru);
> extern void lru_add_page_tail(struct zone* zone,
> - struct page *page, struct page *page_tail);
> + struct page *page, struct page *page_tail,
> + struct list_head *dst);
> extern void activate_page(struct page *);
> extern void mark_page_accessed(struct page *);
> extern void lru_add_drain(void);
> Index: linux/mm/huge_memory.c
> ===================================================================
> --- linux.orig/mm/huge_memory.c 2011-11-02 09:48:16.000000000 +0800
> +++ linux/mm/huge_memory.c 2011-11-02 10:58:21.000000000 +0800
> @@ -1159,7 +1159,8 @@ static int __split_huge_page_splitting(s
> return ret;
> }
>
> -static void __split_huge_page_refcount(struct page *page)
> +static void __split_huge_page_refcount(struct page *page,
> + struct list_head *list)
> {
> int i;
> struct zone *zone = page_zone(page);
> @@ -1229,7 +1230,7 @@ static void __split_huge_page_refcount(s
>
> mem_cgroup_split_huge_fixup(page, page_tail);
>
> - lru_add_page_tail(zone, page, page_tail);
> + lru_add_page_tail(zone, page, page_tail, list);
> }
>
> __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
> @@ -1343,7 +1344,8 @@ static int __split_huge_page_map(struct
>
> /* must be called with anon_vma->root->mutex hold */
> static void __split_huge_page(struct page *page,
> - struct anon_vma *anon_vma)
> + struct anon_vma *anon_vma,
> + struct list_head *list)
> {
> int mapcount, mapcount2;
> struct anon_vma_chain *avc;
> @@ -1375,7 +1377,7 @@ static void __split_huge_page(struct pag
> mapcount, page_mapcount(page));
> BUG_ON(mapcount != page_mapcount(page));
>
> - __split_huge_page_refcount(page);
> + __split_huge_page_refcount(page, list);
>
> mapcount2 = 0;
> list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
> @@ -1392,7 +1394,7 @@ static void __split_huge_page(struct pag
> BUG_ON(mapcount != mapcount2);
> }
>
> -int split_huge_page(struct page *page)
> +int split_huge_page_list(struct page *page, struct list_head *list)
> {
> struct anon_vma *anon_vma;
> int ret = 1;
> @@ -1406,7 +1408,7 @@ int split_huge_page(struct page *page)
> goto out_unlock;
>
> BUG_ON(!PageSwapBacked(page));
> - __split_huge_page(page, anon_vma);
> + __split_huge_page(page, anon_vma, list);
> count_vm_event(THP_SPLIT);
>
> BUG_ON(PageCompound(page));
> Index: linux/mm/swap.c
> ===================================================================
> --- linux.orig/mm/swap.c 2011-11-02 09:48:16.000000000 +0800
> +++ linux/mm/swap.c 2011-11-02 10:06:33.000000000 +0800
> @@ -634,7 +634,8 @@ EXPORT_SYMBOL(__pagevec_release);
>
> /* used by __split_huge_page_refcount() */
> void lru_add_page_tail(struct zone* zone,
> - struct page *page, struct page *page_tail)
> + struct page *page, struct page *page_tail,
> + struct list_head *dst)
> {
> int active;
> enum lru_list lru;
> @@ -646,6 +647,13 @@ void lru_add_page_tail(struct zone* zone
> VM_BUG_ON(PageLRU(page_tail));
> VM_BUG_ON(!spin_is_locked(&zone->lru_lock));
>
> + /* The huge page is isolated */
> + if (dst) {
> + get_page(page_tail);
> + list_add_tail(&page_tail->lru, dst);
> + return;
> + }
> +
> SetPageLRU(page_tail);
>
> if (page_evictable(page_tail, NULL)) {
> Index: linux/mm/swap_state.c
> ===================================================================
> --- linux.orig/mm/swap_state.c 2011-11-02 09:48:16.000000000 +0800
> +++ linux/mm/swap_state.c 2011-11-02 10:06:33.000000000 +0800
> @@ -154,12 +154,6 @@ int add_to_swap(struct page *page)
> if (!entry.val)
> return 0;
>
> - if (unlikely(PageTransHuge(page)))
> - if (unlikely(split_huge_page(page))) {
> - swapcache_free(entry, NULL);
> - return 0;
> - }
> -
> /*
> * Radix-tree node allocations from PF_MEMALLOC contexts could
> * completely exhaust the page allocator. __GFP_NOMEMALLOC
> Index: linux/mm/vmscan.c
> ===================================================================
> --- linux.orig/mm/vmscan.c 2011-11-02 09:48:16.000000000 +0800
> +++ linux/mm/vmscan.c 2011-11-02 10:58:21.000000000 +0800
> @@ -838,6 +838,10 @@ static unsigned long shrink_page_list(st
> if (PageAnon(page) && !PageSwapCache(page)) {
> if (!(sc->gfp_mask & __GFP_IO))
> goto keep_locked;
> + if (unlikely(PageTransHuge(page)))
> + if (unlikely(split_huge_page_list(page,
> + page_list)))
> + goto activate_locked;
> if (!add_to_swap(page))
> goto activate_locked;
> may_enter_fs = 1;
> @@ -1076,7 +1080,8 @@ int __isolate_lru_page(struct page *page
> */
> static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> struct list_head *src, struct list_head *dst,
> - unsigned long *scanned, int order, int mode, int file)
> + unsigned long *scanned, int order, int mode, int file,
> + bool break_on_thp)
> {
Sorry for late response.
These day, I am very busy for new job.
Still, I don't like surgery of isolation part.
What if we isolate a THP page but it is working set page?
Let's assume as follows
1. Ioslate 32 page
2. Unfortunately, 1st page is THP so isolate_lru_page isolates just a
page(of course, it's 512 pages)
3. shrink_page_list see that it's working set page but page_list
have just a page so it have to isolate pages once more with higher priority.
How about this?
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9fdfce7..8121415 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -960,7 +960,15 @@ free_it:
* appear not as the counts should be low
*/
list_add(&page->lru, &free_pages);
- continue;
+
+ /*
+ * If we have reclaimed enough pages, let's cut it off.
+ * It could prevent unnecessary THP split.
+ */
+ if (nr_reclaimed >= sc->nr_to_reclaim)
+ break;
+ else
+ continue;
cull_mlocked:
if (PageSwapCache(page))
> unsigned long nr_taken = 0;
> unsigned long nr_lumpy_taken = 0;
> @@ -1101,6 +1106,10 @@ static unsigned long isolate_lru_pages(u
> list_move(&page->lru, dst);
> mem_cgroup_del_lru(page);
> nr_taken += hpage_nr_pages(page);
> + if (unlikely(PageTransHuge(page)) && break_on_thp) {
> + scan++;
> + goto out;
> + }
> break;
>
> case -EBUSY:
> @@ -1163,6 +1172,8 @@ static unsigned long isolate_lru_pages(u
> if (PageDirty(cursor_page))
> nr_lumpy_dirty++;
> scan++;
> + if (unlikely(PageTransHuge(page)) && break_on_thp)
> + goto out;
> } else {
> /*
> * Check if the page is freed already.
> @@ -1188,6 +1199,7 @@ static unsigned long isolate_lru_pages(u
> nr_lumpy_failed++;
> }
>
> +out:
> *scanned = scan;
>
> trace_mm_vmscan_lru_isolate(order,
> @@ -1202,7 +1214,8 @@ static unsigned long isolate_pages_globa
> struct list_head *dst,
> unsigned long *scanned, int order,
> int mode, struct zone *z,
> - int active, int file)
> + int active, int file,
> + bool break_on_thp)
> {
> int lru = LRU_BASE;
> if (active)
> @@ -1210,7 +1223,7 @@ static unsigned long isolate_pages_globa
> if (file)
> lru += LRU_FILE;
> return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
> - mode, file);
> + mode, file, break_on_thp);
> }
>
> /*
> @@ -1466,7 +1479,7 @@ shrink_inactive_list(unsigned long nr_to
> &page_list, &nr_scanned, sc->order,
> sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
> ISOLATE_BOTH : ISOLATE_INACTIVE,
> - zone, 0, file);
> + zone, 0, file, true);
> zone->pages_scanned += nr_scanned;
> if (current_is_kswapd())
> __count_zone_vm_events(PGSCAN_KSWAPD, zone,
> @@ -1480,7 +1493,7 @@ shrink_inactive_list(unsigned long nr_to
> sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
> ISOLATE_BOTH : ISOLATE_INACTIVE,
> zone, sc->mem_cgroup,
> - 0, file);
> + 0, file, true);
> /*
> * mem_cgroup_isolate_pages() keeps track of
> * scanned pages on its own.
> @@ -1589,13 +1602,13 @@ static void shrink_active_list(unsigned
> nr_taken = isolate_pages_global(nr_pages, &l_hold,
> &pgscanned, sc->order,
> ISOLATE_ACTIVE, zone,
> - 1, file);
> + 1, file, false);
> zone->pages_scanned += pgscanned;
> } else {
> nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
> &pgscanned, sc->order,
> ISOLATE_ACTIVE, zone,
> - sc->mem_cgroup, 1, file);
> + sc->mem_cgroup, 1, file, false);
> /*
> * mem_cgroup_isolate_pages() keeps track of
> * scanned pages on its own.
> Index: linux/include/linux/memcontrol.h
> ===================================================================
> --- linux.orig/include/linux/memcontrol.h 2011-11-02 09:48:16.000000000 +0800
> +++ linux/include/linux/memcontrol.h 2011-11-02 10:06:33.000000000 +0800
> @@ -37,7 +37,8 @@ extern unsigned long mem_cgroup_isolate_
> unsigned long *scanned, int order,
> int mode, struct zone *z,
> struct mem_cgroup *mem_cont,
> - int active, int file);
> + int active, int file,
> + bool break_on_thp);
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> /*
> Index: linux/mm/memcontrol.c
> ===================================================================
> --- linux.orig/mm/memcontrol.c 2011-11-02 09:48:16.000000000 +0800
> +++ linux/mm/memcontrol.c 2011-11-02 10:06:33.000000000 +0800
> @@ -1187,7 +1187,8 @@ unsigned long mem_cgroup_isolate_pages(u
> unsigned long *scanned, int order,
> int mode, struct zone *z,
> struct mem_cgroup *mem_cont,
> - int active, int file)
> + int active, int file,
> + bool break_on_thp)
> {
> unsigned long nr_taken = 0;
> struct page *page;
> @@ -1225,6 +1226,8 @@ unsigned long mem_cgroup_isolate_pages(u
> list_move(&page->lru, dst);
> mem_cgroup_del_lru(page);
> nr_taken += hpage_nr_pages(page);
> + if (unlikely(PageTransHuge(page)) && break_on_thp)
> + goto out;
> break;
> case -EBUSY:
> /* we don't affect global LRU but rotate in our LRU */
> @@ -1235,6 +1238,7 @@ unsigned long mem_cgroup_isolate_pages(u
> }
> }
>
> +out:
> *scanned = scan;
>
> trace_mm_vmscan_memcg_isolate(0, nr_to_scan, scan, nr_taken,
>
>
--
Kind regards,
Minchan Kim
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