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Date: Tue, 6 Mar 2012 15:57:37 +0400
From: Glauber Costa <glommer@...allels.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC: Konstantin Khlebnikov <khlebnikov@...nvz.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>,
Johannes Weiner <jweiner@...hat.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7] mm: rework __isolate_lru_page() file/anon filter
On 03/02/2012 12:17 PM, KAMEZAWA Hiroyuki wrote:
> On Fri, 02 Mar 2012 09:51:27 +0400
> Konstantin Khlebnikov<khlebnikov@...nvz.org> wrote:
>
>> KAMEZAWA Hiroyuki wrote:
>>> On Wed, 29 Feb 2012 13:15:47 +0400
>>> Konstantin Khlebnikov<khlebnikov@...nvz.org> wrote:
>>>
>>>> This patch adds file/anon filter bits into isolate_mode_t,
>>>> this allows to simplify checks in __isolate_lru_page().
>>>>
>>>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>>>
>>> Hmm.. I like idea but..
>>>
>>>> ---
>>>> include/linux/mmzone.h | 4 ++++
>>>> include/linux/swap.h | 2 +-
>>>> mm/compaction.c | 5 +++--
>>>> mm/vmscan.c | 27 +++++++++++++--------------
>>>> 4 files changed, 21 insertions(+), 17 deletions(-)
>>>>
>>>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>>>> index eff4918..2fed935 100644
>>>> --- a/include/linux/mmzone.h
>>>> +++ b/include/linux/mmzone.h
>>>> @@ -193,6 +193,10 @@ struct lruvec {
>>>> #define ISOLATE_UNMAPPED ((__force isolate_mode_t)0x8)
>>>> /* Isolate for asynchronous migration */
>>>> #define ISOLATE_ASYNC_MIGRATE ((__force isolate_mode_t)0x10)
>>>> +/* Isolate swap-backed pages */
>>>> +#define ISOLATE_ANON ((__force isolate_mode_t)0x20)
>>>> +/* Isolate file-backed pages */
>>>> +#define ISOLATE_FILE ((__force isolate_mode_t)0x40)
>>>>
>>>> /* LRU Isolation modes. */
>>>> typedef unsigned __bitwise__ isolate_mode_t;
>>>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>>>> index ba2c8d7..dc6e6a3 100644
>>>> --- a/include/linux/swap.h
>>>> +++ b/include/linux/swap.h
>>>> @@ -254,7 +254,7 @@ static inline void lru_cache_add_file(struct page *page)
>>>> /* linux/mm/vmscan.c */
>>>> extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
>>>> gfp_t gfp_mask, nodemask_t *mask);
>>>> -extern int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file);
>>>> +extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
>>>> extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
>>>> gfp_t gfp_mask, bool noswap);
>>>> extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
>>>> diff --git a/mm/compaction.c b/mm/compaction.c
>>>> index 74a8c82..cc054f7 100644
>>>> --- a/mm/compaction.c
>>>> +++ b/mm/compaction.c
>>>> @@ -261,7 +261,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
>>>> unsigned long last_pageblock_nr = 0, pageblock_nr;
>>>> unsigned long nr_scanned = 0, nr_isolated = 0;
>>>> struct list_head *migratelist =&cc->migratepages;
>>>> - isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
>>>> + isolate_mode_t mode = ISOLATE_ACTIVE | ISOLATE_INACTIVE |
>>>> + ISOLATE_FILE | ISOLATE_ANON;
>>>>
>>>> /* Do not scan outside zone boundaries */
>>>> low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
>>>> @@ -375,7 +376,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
>>>> mode |= ISOLATE_ASYNC_MIGRATE;
>>>>
>>>> /* Try isolate the page */
>>>> - if (__isolate_lru_page(page, mode, 0) != 0)
>>>> + if (__isolate_lru_page(page, mode) != 0)
>>>> continue;
>>>>
>>>> VM_BUG_ON(PageTransCompound(page));
>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>> index af6cfe7..1b70338 100644
>>>> --- a/mm/vmscan.c
>>>> +++ b/mm/vmscan.c
>>>> @@ -1029,27 +1029,18 @@ keep_lumpy:
>>>> *
>>>> * returns 0 on success, -ve errno on failure.
>>>> */
>>>> -int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
>>>> +int __isolate_lru_page(struct page *page, isolate_mode_t mode)
>>>> {
>>>> - bool all_lru_mode;
>>>> int ret = -EINVAL;
>>>>
>>>> /* Only take pages on the LRU. */
>>>> if (!PageLRU(page))
>>>> return ret;
>>>>
>>>> - all_lru_mode = (mode& (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
>>>> - (ISOLATE_ACTIVE|ISOLATE_INACTIVE);
>>>> -
>>>> - /*
>>>> - * When checking the active state, we need to be sure we are
>>>> - * dealing with comparible boolean values. Take the logical not
>>>> - * of each.
>>>> - */
>>>> - if (!all_lru_mode&& !PageActive(page) != !(mode& ISOLATE_ACTIVE))
>>>> + if (!(mode& (PageActive(page) ? ISOLATE_ACTIVE : ISOLATE_INACTIVE)))
>>>> return ret;
>>>
>>> Isn't this complicated ?
>>
>> But it doesn't blows my mind as old code does =)
>>
>> Maybe someone can propose more clear variant?
>>
>
> switch (mode& (ISOLATE_ACTIVE | ISOLATE_INACTIVE)) {
> case ISOLATE_ACTIVE :
> if (!PageActive(page))
> return ret;
> case ISOLATE_INACTIVE :
> if (PageActive(page))
> return ret;
> default:
> break;
> }
> }
>
> ?
>
> Thanks,
> -Kame
>
The switch gets a little bit too big (vertical-wise). Maybe just
splitting it into two lines is enough to clarify its purpose.
How about:
int tmp_var = PageActive(page) ? ISOLATE_ACTIVE : ISOLATE_INACTIVE
if (!(mode & tmp_var))
ret;
--
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