Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [RFC][PATCH] proc: export more page flags in /proc/kpageflags | Date | Tue, 14 Apr 2009 16:17:09 +0900 (JST) |
| |
> 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.
| |