From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> To: Andi Kleen <andi@firstfloor.org> Cc: kosaki.motohiro@jp.fujitsu.com, Wu Fengguang <fengguang.wu@intel.com>, Andrew Morton <akpm@linux-foundation.org>, LKML <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org> Subject: Re: [RFC][PATCH] proc: export more page flags in /proc/kpageflags Date: Tue, 14 Apr 2009 16:17:09 +0900 (JST) [thread overview] Message-ID: <20090414161211.C66E.A69D9226@jp.fujitsu.com> (raw) In-Reply-To: <20090414071159.GV14687@one.firstfloor.org> > 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?) > > 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. OK. rest problem is, how do we write document this. PG_reserved have multiple meanings... > > > > > - 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. Ah good idea. > > > > > > > > > > - 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. Yes, I agree. > > > > > - 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. PG_unevictable and PG_mlocked have a bit delicate meaning. it gurantee the page isn't evicted. but mlock(2) don't gurantee turn page on PG_mlocked. some race prevent it. I'm afraid administrator confuse it. but if someone can write good document, my worriness will vanished.
WARNING: multiple messages have this Message-ID (diff)
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> To: Andi Kleen <andi@firstfloor.org> Cc: kosaki.motohiro@jp.fujitsu.com, Wu Fengguang <fengguang.wu@intel.com>, Andrew Morton <akpm@linux-foundation.org>, LKML <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org> Subject: Re: [RFC][PATCH] proc: export more page flags in /proc/kpageflags Date: Tue, 14 Apr 2009 16:17:09 +0900 (JST) [thread overview] Message-ID: <20090414161211.C66E.A69D9226@jp.fujitsu.com> (raw) In-Reply-To: <20090414071159.GV14687@one.firstfloor.org> > 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?) > > 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. OK. rest problem is, how do we write document this. PG_reserved have multiple meanings... > > > > > - 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. Ah good idea. > > > > > > > > > > - 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. Yes, I agree. > > > > > - 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. PG_unevictable and PG_mlocked have a bit delicate meaning. it gurantee the page isn't evicted. but mlock(2) don't gurantee turn page on PG_mlocked. some race prevent it. I'm afraid administrator confuse it. but if someone can write good document, my worriness will vanished. -- 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/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2009-04-14 7:17 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-04-14 4:22 [RFC][PATCH] proc: export more page flags in /proc/kpageflags Wu Fengguang 2009-04-14 4:22 ` Wu Fengguang 2009-04-14 4:36 ` Wu Fengguang 2009-04-14 4:37 ` KOSAKI Motohiro 2009-04-14 4:37 ` KOSAKI Motohiro 2009-04-14 6:41 ` Wu Fengguang 2009-04-14 6:41 ` Wu Fengguang 2009-04-14 6:54 ` KOSAKI Motohiro 2009-04-14 6:54 ` KOSAKI Motohiro 2009-04-14 7:11 ` Andi Kleen 2009-04-14 7:11 ` Andi Kleen 2009-04-14 7:17 ` KOSAKI Motohiro [this message] 2009-04-14 7:17 ` KOSAKI Motohiro 2009-04-15 13:18 ` Wu Fengguang 2009-04-15 13:18 ` Wu Fengguang 2009-04-15 13:57 ` Andi Kleen 2009-04-15 13:57 ` Andi Kleen 2009-04-16 2:41 ` Wu Fengguang 2009-04-16 2:41 ` Wu Fengguang 2009-04-16 3:54 ` Andi Kleen 2009-04-16 3:54 ` Andi Kleen 2009-04-16 4:43 ` Wu Fengguang 2009-04-16 4:43 ` Wu Fengguang 2009-04-16 2:26 ` KOSAKI Motohiro 2009-04-16 2:26 ` KOSAKI Motohiro 2009-04-16 3:49 ` Wu Fengguang 2009-04-16 3:49 ` Wu Fengguang 2009-04-16 6:30 ` Wu Fengguang 2009-04-16 6:30 ` Wu Fengguang 2009-04-23 2:26 ` [RFC][PATCH] proc: export more page flags in /proc/kpageflags (take 3) Wu Fengguang 2009-04-23 2:26 ` Wu Fengguang 2009-04-23 7:48 ` Andi Kleen 2009-04-23 7:48 ` Andi Kleen 2009-04-23 8:10 ` Wu Fengguang 2009-04-23 8:10 ` Wu Fengguang 2009-04-23 8:54 ` Andi Kleen 2009-04-23 8:54 ` Andi Kleen 2009-04-23 11:21 ` Wu Fengguang 2009-04-23 11:21 ` Wu Fengguang 2009-04-25 1:59 ` Wu Fengguang 2009-04-14 7:22 ` [RFC][PATCH] proc: export more page flags in /proc/kpageflags Wu Fengguang 2009-04-14 7:22 ` Wu Fengguang 2009-04-14 7:42 ` KOSAKI Motohiro 2009-04-14 7:42 ` KOSAKI Motohiro
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