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Message-Id: <20140912165143.86d5f83dcde4a9fd78069f79@linux-foundation.org>
Date: Fri, 12 Sep 2014 16:51:43 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Konstantin Khlebnikov <koct9i@...il.com>
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, 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, 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?
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?
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.
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
_
--
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