linux-kernel - Re: [PATCH -mm 13/25] Noreclaim LRU Infrastructure

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Message-ID: <2f11576a0806081407l5d26d229ye252ff378434e787@mail.gmail.com>
Date:	Mon, 9 Jun 2008 06:07:09 +0900
From:	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
To:	"Rik van Riel" <riel@...hat.com>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, lee.schermerhorn@...com,
	linux-mm@...ck.org, eric.whitney@...com
Subject: Re: [PATCH -mm 13/25] Noreclaim LRU Infrastructure

>> > +#ifdef CONFIG_NORECLAIM_LRU
>> > +   PG_noreclaim,           /* Page is "non-reclaimable"  */
>> > +#endif
>>
>> I fear that we're messing up the terminology here.
>>
>> Go into your 2.6.25 tree and do `grep -i reclaimable */*.c'.  The term
>> already means a few different things, but in the vmscan context,
>> "reclaimable" means that the page is unreferenced, clean and can be
>> stolen.  "reclaimable" also means a lot of other things, and we just
>> made that worse.
>>
>> Can we think of a new term which uniquely describes this new concept
>> and use that, rather than flogging the old horse?
>
> Want to reuse the BSD term "pinned" instead?

I like this term :)
but I afraid to somebody confuse Xen/KVM term's pinned page.
IOW, I guess somebody imazine from "pinned page" to below flag.

#define PG_pinned               PG_owner_priv_1 /* Xen pinned pagetable */

I have no idea....


>> > +/**
>> > + * add_page_to_noreclaim_list
>> > + * @page:  the page to be added to the noreclaim list
>> > + *
>> > + * Add page directly to its zone's noreclaim list.  To avoid races with
>> > + * tasks that might be making the page reclaimble while it's not on the
>> > + * lru, we want to add the page while it's locked or otherwise "invisible"
>> > + * to other tasks.  This is difficult to do when using the pagevec cache,
>> > + * so bypass that.
>> > + */
>>
>> How does a task "make a page reclaimable"?  munlock()?  fsync()?
>> exit()?
>>
>> Choice of terminology matters...
>
> Lee?  Kosaki-san?

IFAIK, moving noreclaim list to reclaim list happend at below situation.

mlock'ed page
  - all mlocked process exit.
  - all mlocked process call munlock().
  - page related vma vanished
    (e.g. mumap, mmap, remap_file_page)

SHM_LOCKed page
  -  sysctl(SHM_UNLOCK) called.
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