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Date: Wed, 15 Apr 2009 21:18:00 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Andi Kleen <andi@...stfloor.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [RFC][PATCH] proc: export more page flags in /proc/kpageflags
On Tue, Apr 14, 2009 at 03:11:59PM +0800, Andi Kleen wrote:
> On Tue, Apr 14, 2009 at 03:54:40PM +0900, KOSAKI Motohiro wrote:
> > Hi
>
> There are two use cases here:
>
> First what is useful for the administrator as a general abstraction.
> And what is useful for the kernel hacker for debugging.
>
> The kernel hacker wants everything even if it's subject to change,
> the administrator wants a higher level abstraction they can make
> sense of and that doesn't change too often.
>
> I think there's a case for both usages, but perhaps they
> should be separated (in a public and a internal interface perhaps?)
That's pretty good separations. I guess it would be convenient to make the
extra kernel flags available under CONFIG_DEBUG_KERNEL?
> My comments below are about abstractions for the first case.
>
>
> >
> > > On Tue, Apr 14, 2009 at 12:37:10PM +0800, KOSAKI Motohiro wrote:
> > > > > Export the following page flags in /proc/kpageflags,
> > > > > just in case they will be useful to someone:
> > > > >
> > > > > - PG_swapcache
> > > > > - PG_swapbacked
> > > > > - PG_mappedtodisk
> > > > > - PG_reserved
>
> PG_reserved should be exported as PG_KERNEL or somesuch.
PG_KERNEL could be misleading. PG_reserved obviously do not cover all
(or most) kernel pages. So I'd prefer to export PG_reserved as it is.
It seems that the vast amount of free pages are marked PG_reserved:
# uname -a
Linux hp 2.6.30-rc2 #157 SMP Wed Apr 15 19:37:49 CST 2009 x86_64 GNU/Linux
# echo 1 > /proc/sys/vm/drop_caches
# ./page-types
flags page-count MB symbolic-flags long-symbolic-flags
0x004000 497474 1943 ______________r_____ reserved
0x008000 4454 17 _______________o____ compound
0x008014 5 0 __R_D__________o____ referenced,dirty,compound
0x000020 1 0 _____l______________ lru
0x000028 310 1 ___U_l______________ uptodate,lru
0x00002c 18 0 __RU_l______________ referenced,uptodate,lru
0x000068 80 0 ___U_lA_____________ uptodate,lru,active
0x00006c 157 0 __RU_lA_____________ referenced,uptodate,lru,active
0x002078 1 0 ___UDlA______b______ uptodate,dirty,lru,active,swapbacked
0x00207c 17 0 __RUDlA______b______ referenced,uptodate,dirty,lru,active,swapbacked
0x000228 13 0 ___U_l___x__________ uptodate,lru,reclaim
0x000400 2085 8 __________B_________ buddy
0x000804 1 0 __R________m________ referenced,mmap
0x002808 10 0 ___U_______m_b______ uptodate,mmap,swapbacked
0x000828 1060 4 ___U_l_____m________ uptodate,lru,mmap
0x00082c 215 0 __RU_l_____m________ referenced,uptodate,lru,mmap
0x000868 189 0 ___U_lA____m________ uptodate,lru,active,mmap
0x002868 4187 16 ___U_lA____m_b______ uptodate,lru,active,mmap,swapbacked
0x00286c 30 0 __RU_lA____m_b______ referenced,uptodate,lru,active,mmap,swapbacked
0x00086c 1012 3 __RU_lA____m________ referenced,uptodate,lru,active,mmap
0x002878 3 0 ___UDlA____m_b______ uptodate,dirty,lru,active,mmap,swapbacked
0x008880 936 3 _______S___m___o____ slab,mmap,compound
0x000880 1602 6 _______S___m________ slab,mmap
0x0088c0 59 0 ______AS___m___o____ active,slab,mmap,compound
0x0008c0 49 0 ______AS___m________ active,slab,mmap
total 513968 2007
# ./page-areas 0x004000
offset len KB
0 15 60KB
31 4 16KB
159 97 388KB
4096 2213 8852KB
6899 2385 9540KB
9497 3 12KB
9728 14528 58112KB
> > > > > - PG_private
> > > > > - PG_private_2
> > > > > - PG_owner_priv_1
> > > > >
> > > > > - PG_head
> > > > > - PG_tail
> > > > > - PG_compound
>
> I would combine these three into a pseudo "large page" flag.
Very neat idea! Patch updated accordingly.
However - one pity I observed:
# ./page-areas 0x008000
offset len KB
3088 4 16KB
We can no longer tell if the above line means one 4-page hugepage, or two
2-page hugepages... Adding PG_COMPOUND_TAIL into the CONFIG_DEBUG_KERNEL block
can help kernel developers. Or will it be ever cared by administrators?
341196 2 8KB
341202 2 8KB
341262 2 8KB
341272 8 32KB
341296 8 32KB
488448 24 96KB
488490 2 8KB
488496 320 1280KB
488842 2 8KB
488848 40 160KB
> > > > >
> > > > > - PG_unevictable
> > > > > - PG_mlocked
> > > > >
> > > > > - PG_poison
>
> PG_poison is also useful to export. But since it depends on my
> patchkit I will pull a patch for that into the HWPOISON series.
That's not a problem - since the PG_poison line is be protected by
#ifdef CONFIG_MEMORY_FAILURE :-)
> > > > > - PG_unevictable
> > > > > - PG_mlocked
> >
> > this 9 flags shouldn't exported.
> > I can't imazine administrator use what purpose those flags.
>
> I think an abstraced "PG_pinned" or somesuch flag that combines
> page lock, unevictable, mlocked would be useful for the administrator.
The PG_PINNED abstraction risks hiding useful information.
The administrator may not only care about the pinned pages,
but also care _why_ they are pinned, i.e. ramfs.. or mlock?
So it might be good to export them as is, with proper document.
Here is the v2 patch, with flags for kernel hackers numbered from 32.
Comments are welcome!
Thanks,
Fengguang
---
Export all available page flags in /proc/kpageflags, plus two pseudo ones.
This increases the total number of exported page flags to 26.
TODO: more document
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Matt Mackall <mpm@...enic.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>
Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
---
fs/proc/page.c | 122 +++++++++++++++++++++++++++++++++++------------
1 file changed, 91 insertions(+), 31 deletions(-)
--- mm.orig/fs/proc/page.c
+++ mm/fs/proc/page.c
@@ -68,20 +68,96 @@ static const struct file_operations proc
/* These macros are used to decouple internal flags from exported ones */
-#define KPF_LOCKED 0
-#define KPF_ERROR 1
-#define KPF_REFERENCED 2
-#define KPF_UPTODATE 3
-#define KPF_DIRTY 4
-#define KPF_LRU 5
-#define KPF_ACTIVE 6
-#define KPF_SLAB 7
-#define KPF_WRITEBACK 8
-#define KPF_RECLAIM 9
-#define KPF_BUDDY 10
+#define KPF_LOCKED 0
+#define KPF_ERROR 1
+#define KPF_REFERENCED 2
+#define KPF_UPTODATE 3
+#define KPF_DIRTY 4
+#define KPF_LRU 5
+#define KPF_ACTIVE 6
+#define KPF_SLAB 7
+#define KPF_WRITEBACK 8
+#define KPF_RECLAIM 9
+#define KPF_BUDDY 10
+
+/* new additions in 2.6.31 */
+#define KPF_MMAP 11
+#define KPF_SWAPCACHE 12
+#define KPF_SWAPBACKED 13
+#define KPF_RESERVED 14
+#define KPF_COMPOUND 15
+#define KPF_UNEVICTABLE 16
+#define KPF_MLOCKED 17
+#define KPF_POISON 18
+#define KPF_NOPAGE 19
+
+/* kernel hacking assistances */
+#define KPF_MAPPEDTODISK 32
+#define KPF_PRIVATE 33
+#define KPF_PRIVATE2 34
+#define KPF_OWNER_PRIVATE 35
+#define KPF_ARCH 36
+#define KPF_UNCACHED 37
#define kpf_copy_bit(flags, dstpos, srcpos) (((flags >> srcpos) & 1) << dstpos)
+u64 get_uflags(struct page *page)
+{
+ u64 kflags;
+ u64 uflags;
+
+ if (!page)
+ return 1 << KPF_NOPAGE;
+
+ kflags = page->flags;
+ uflags = 0;
+
+ if (page_mapped(page))
+ uflags |= 1 << KPF_MMAP;
+
+ uflags |= kpf_copy_bit(kflags, KPF_LOCKED, PG_locked);
+ uflags |= kpf_copy_bit(kflags, KPF_ERROR, PG_error);
+ uflags |= kpf_copy_bit(kflags, KPF_REFERENCED, PG_referenced);
+ uflags |= kpf_copy_bit(kflags, KPF_UPTODATE, PG_uptodate);
+ uflags |= kpf_copy_bit(kflags, KPF_DIRTY, PG_dirty);
+ uflags |= kpf_copy_bit(kflags, KPF_LRU, PG_lru) ;
+ uflags |= kpf_copy_bit(kflags, KPF_ACTIVE, PG_active);
+ uflags |= kpf_copy_bit(kflags, KPF_SLAB, PG_slab);
+ uflags |= kpf_copy_bit(kflags, KPF_WRITEBACK, PG_writeback);
+ uflags |= kpf_copy_bit(kflags, KPF_RECLAIM, PG_reclaim);
+ uflags |= kpf_copy_bit(kflags, KPF_BUDDY, PG_buddy);
+
+ uflags |= kpf_copy_bit(kflags, KPF_SWAPCACHE, PG_swapcache);
+ uflags |= kpf_copy_bit(kflags, KPF_SWAPBACKED, PG_swapbacked);
+ uflags |= kpf_copy_bit(kflags, KPF_RESERVED, PG_reserved);
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+ uflags |= kpf_copy_bit(kflags, KPF_COMPOUND, PG_head);
+ uflags |= kpf_copy_bit(kflags, KPF_COMPOUND, PG_tail);
+#else
+ uflags |= kpf_copy_bit(kflags, KPF_COMPOUND, PG_compound);
+#endif
+#ifdef CONFIG_UNEVICTABLE_LRU
+ uflags |= kpf_copy_bit(kflags, KPF_UNEVICTABLE, PG_unevictable);
+ uflags |= kpf_copy_bit(kflags, KPF_MLOCKED, PG_mlocked);
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+ uflags |= kpf_copy_bit(kflags, KPF_POISON, PG_poison);
+#endif
+
+#ifdef CONFIG_DEBUG_KERNEL
+ uflags |= kpf_copy_bit(kflags, KPF_MAPPEDTODISK, PG_mappedtodisk);
+ uflags |= kpf_copy_bit(kflags, KPF_PRIVATE, PG_private);
+ uflags |= kpf_copy_bit(kflags, KPF_PRIVATE2, PG_private_2);
+ uflags |= kpf_copy_bit(kflags, KPF_OWNER_PRIVATE, PG_owner_priv_1);
+ uflags |= kpf_copy_bit(kflags, KPF_ARCH, PG_arch_1);
+#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
+ uflags |= kpf_copy_bit(kflags, KPF_UNCACHED, PG_uncached);
+#endif
+#endif
+
+ return uflags;
+};
+
static ssize_t kpageflags_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
@@ -90,7 +166,6 @@ static ssize_t kpageflags_read(struct fi
unsigned long src = *ppos;
unsigned long pfn;
ssize_t ret = 0;
- u64 kflags, uflags;
pfn = src / KPMSIZE;
count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
@@ -98,32 +173,17 @@ static ssize_t kpageflags_read(struct fi
return -EINVAL;
while (count > 0) {
- ppage = NULL;
if (pfn_valid(pfn))
ppage = pfn_to_page(pfn);
- pfn++;
- if (!ppage)
- kflags = 0;
else
- kflags = ppage->flags;
-
- uflags = kpf_copy_bit(kflags, KPF_LOCKED, PG_locked) |
- kpf_copy_bit(kflags, KPF_ERROR, PG_error) |
- kpf_copy_bit(kflags, KPF_REFERENCED, PG_referenced) |
- kpf_copy_bit(kflags, KPF_UPTODATE, PG_uptodate) |
- kpf_copy_bit(kflags, KPF_DIRTY, PG_dirty) |
- kpf_copy_bit(kflags, KPF_LRU, PG_lru) |
- kpf_copy_bit(kflags, KPF_ACTIVE, PG_active) |
- kpf_copy_bit(kflags, KPF_SLAB, PG_slab) |
- kpf_copy_bit(kflags, KPF_WRITEBACK, PG_writeback) |
- kpf_copy_bit(kflags, KPF_RECLAIM, PG_reclaim) |
- kpf_copy_bit(kflags, KPF_BUDDY, PG_buddy);
+ ppage = NULL;
- if (put_user(uflags, out++)) {
+ if (put_user(get_uflags(ppage), out)) {
ret = -EFAULT;
break;
}
-
+ out++;
+ pfn++;
count -= KPMSIZE;
}
--
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