Re: [PATCH 2/3] check unevictable flag in lumy reclaim v2

[Minchan Kim]

On Thu, Jun 11, 2009 at 6:37 PM, Minchan Kim<minchan.kim@xxxxxxxxx> wrote:
> On Thu, Jun 11, 2009 at 5:38 PM, KAMEZAWA
> Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
>> How about this ?
>>
>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>>
>> Lumpy reclaim check pages from their pfn. Then, it can find unevictable pages
>> in its loop.
>> Abort lumpy reclaim when we find Unevictable page, we never get a lump
>> of pages for requested order.
>>
>> Changelog: v1->v2
>> Â- rewrote commet.
>>
>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>> ---
>> Âmm/vmscan.c | Â Â9 +++++++++
>> Â1 file changed, 9 insertions(+)
>>
>> Index: lumpy-reclaim-trial/mm/vmscan.c
>> ===================================================================
>> --- lumpy-reclaim-trial.orig/mm/vmscan.c
>> +++ lumpy-reclaim-trial/mm/vmscan.c
>> @@ -936,6 +936,15 @@ static unsigned long isolate_lru_pages(u
>> Â Â Â Â Â Â Â Â Â Â Â Â/* Check that we have not crossed a zone boundary. */
>> Â Â Â Â Â Â Â Â Â Â Â Âif (unlikely(page_zone_id(cursor_page) != zone_id))
>> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Âcontinue;
>> + Â Â Â Â Â Â Â Â Â Â Â /*
>> + Â Â Â Â Â Â Â Â Â Â Â Â* We tries to free all pages in this range to create
>> + Â Â Â Â Â Â Â Â Â Â Â Â* a free large page. Then, if the range includes a page
>> + Â Â Â Â Â Â Â Â Â Â Â Â* never be reclaimed, we have no reason to do more.
>> + Â Â Â Â Â Â Â Â Â Â Â Â* PageUnevictable page is not a page which can be
>> + Â Â Â Â Â Â Â Â Â Â Â Â* easily freed. Abort this scan now.
>> + Â Â Â Â Â Â Â Â Â Â Â Â*/
>> + Â Â Â Â Â Â Â Â Â Â Â if (unlikely(PageUnevictable(cursor_page)))
>> + Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â break;
>
> __isolate_lru_pages already checked PageUnevictable to return error.
> I want to remove repeated check although it is trivial.
>
> By your patch, It seems to remove PageUnevictable check in __isolate_lru_pages.

typo.

It seems we can remove PageUnevictable check in __isolate_lru_pages.
Sorry for noise.

> But I know that. If we remove PageUnevictable check in
> __isolate_lru_pages, it can't go into BUG in non-lumpy case. ( I
> mentioned following as code)
>
> Â Â Â Â Â Â Â Âcase -EBUSY:
> Â Â Â Â Â Â Â Â Â Â Â Â/* else it is being freed elsewhere */
> Â Â Â Â Â Â Â Â Â Â Â Âlist_move(&page->lru, src);
> Â Â Â Â Â Â Â Â Â Â Â Âcontinue;
>
> Â Â Â Â Â Â Â Âdefault:
> Â Â Â Â Â Â Â Â Â Â Â ÂBUG();
> Â Â Â Â Â Â Â Â}
>
>
> It means we can remove BUG in non-lumpy case and then add BUG into
> __isolate_lru_pages directly.
>
> If we can do it, we can remove unnecessary PageUnevictable check in
> __isolate_lru_page.
>
> I am not sure this is right in case of memcg.
>
> --
> Kinds regards,
> Minchan Kim
>



-- 
Kinds regards,
Minchan Kim
--
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