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Message-ID: <CALYGNiM0Uh1KG8Z6pFEAn=uxZBRPfHDffXjKkKJoG-K0hCaqaA@mail.gmail.com> Date: Sat, 13 Sep 2014 09:26:49 +0400 From: Konstantin Khlebnikov <koct9i@...il.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Konstantin Khlebnikov <k.khlebnikov@...sung.com>, Rafael Aquini <aquini@...hat.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, Andrey Ryabinin <ryabinin.a.a@...il.com>, Sasha Levin <sasha.levin@...cle.com> Subject: Re: [PATCH v2 4/6] mm: introduce common page state for ballooned memory On Sat, Sep 13, 2014 at 3:51 AM, Andrew Morton <akpm@...ux-foundation.org> wrote: > On Sat, 30 Aug 2014 20:41:20 +0400 Konstantin Khlebnikov <koct9i@...il.com> wrote: > >> This patch adds page state PageBallon() and functions __Set/ClearPageBalloon. >> Like PageBuddy() PageBalloon() looks like page-flag but actually this is special >> state of page->_mapcount counter. There is no conflict because ballooned pages >> cannot be mapped and cannot be in buddy allocator. >> >> Ballooned pages are counted in vmstat counter NR_BALLOON_PAGES, it's shown them >> in /proc/meminfo and /proc/meminfo. Also this patch it exports PageBallon into >> userspace via /proc/kpageflags as KPF_BALLOON. >> >> All new code is under CONFIG_MEMORY_BALLOON, it should be selected by >> ballooning driver which wants use this feature. > > The delta from the (fixed) v1 is below. > > What's up with those Kconfig/Makefile changes? We're now including a > pile of balloon code into vmlinux when CONFIG_MEMORY_BALLOON=n? These > changes were not changelogged? It's been moved into next patch, and not mentioned in changes. Sorry. > > Did we really need to put the BalloonPages count into per-zone vmstat, > global vmstat and /proc/meminfo? Seems a bit overkillish - why so > important? Balloon grabs random pages, their distribution among numa nodes might be important. But I know nobody who uses numa-aware vm together with ballooning. Probably it's better to drop per-zone vmstat and line from meminfo, global vmstat counter should be enough. > > Consuming another page flag is a big deal. We keep on nearly running > out and one day we'll run out for real. page-flags-layout.h is > incomprehensible. How many flags do we have left (worst-case) with this > change? Is there no other way? Needs extraordinary justification, > please. PageBalloon is not a page flags, it's like PageBuddy -- special state of _mapcount (-256 in this case). The same was in v1 and is written in the comment above. > > drivers/virtio/Kconfig | 1 - > include/linux/mm.h | 14 ++++++++++++-- > mm/Makefile | 3 +-- > mm/balloon_compaction.c | 16 ---------------- > 4 files changed, 13 insertions(+), 21 deletions(-) > > diff -puN drivers/virtio/Kconfig~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 drivers/virtio/Kconfig > --- a/drivers/virtio/Kconfig~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 > +++ a/drivers/virtio/Kconfig > @@ -25,7 +25,6 @@ config VIRTIO_PCI > config VIRTIO_BALLOON > tristate "Virtio balloon driver" > depends on VIRTIO > - select MEMORY_BALLOON > ---help--- > This driver supports increasing and decreasing the amount > of memory within a KVM guest. > diff -puN include/linux/mm.h~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 include/linux/mm.h > --- a/include/linux/mm.h~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 > +++ a/include/linux/mm.h > @@ -561,8 +561,18 @@ static inline int PageBalloon(struct pag > return IS_ENABLED(CONFIG_MEMORY_BALLOON) && > atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE; > } > -void __SetPageBalloon(struct page *page); > -void __ClearPageBalloon(struct page *page); > + > +static inline void __SetPageBalloon(struct page *page) > +{ > + VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page); > + atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE); > +} > + > +static inline void __ClearPageBalloon(struct page *page) > +{ > + VM_BUG_ON_PAGE(!PageBalloon(page), page); > + atomic_set(&page->_mapcount, -1); > +} > > void put_page(struct page *page); > void put_pages_list(struct list_head *pages); > diff -puN mm/Makefile~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 mm/Makefile > --- a/mm/Makefile~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 > +++ a/mm/Makefile > @@ -16,7 +16,7 @@ obj-y := filemap.o mempool.o oom_kill. > readahead.o swap.o truncate.o vmscan.o shmem.o \ > util.o mmzone.o vmstat.o backing-dev.o \ > mm_init.o mmu_context.o percpu.o slab_common.o \ > - compaction.o vmacache.o \ > + compaction.o balloon_compaction.o vmacache.o \ > interval_tree.o list_lru.o workingset.o \ > iov_iter.o $(mmu-y) > > @@ -64,4 +64,3 @@ obj-$(CONFIG_ZBUD) += zbud.o > obj-$(CONFIG_ZSMALLOC) += zsmalloc.o > obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o > obj-$(CONFIG_CMA) += cma.o > -obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o > diff -puN mm/balloon_compaction.c~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 mm/balloon_compaction.c > --- a/mm/balloon_compaction.c~mm-introduce-common-page-state-for-ballooned-memory-fix-v2 > +++ a/mm/balloon_compaction.c > @@ -10,22 +10,6 @@ > #include <linux/export.h> > #include <linux/balloon_compaction.h> > > -void __SetPageBalloon(struct page *page) > -{ > - VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page); > - atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE); > - inc_zone_page_state(page, NR_BALLOON_PAGES); > -} > -EXPORT_SYMBOL(__SetPageBalloon); > - > -void __ClearPageBalloon(struct page *page) > -{ > - VM_BUG_ON_PAGE(!PageBalloon(page), page); > - atomic_set(&page->_mapcount, -1); > - dec_zone_page_state(page, NR_BALLOON_PAGES); > -} > -EXPORT_SYMBOL(__ClearPageBalloon); > - > /* > * balloon_devinfo_alloc - allocates a balloon device information descriptor. > * @balloon_dev_descriptor: pointer to reference the balloon device which > _ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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