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SubjectRe: [PATCH 3/7] mm: rework __isolate_lru_page() file/anon filter
Glauber Costa wrote:
> On 03/02/2012 12:17 PM, KAMEZAWA Hiroyuki wrote:
>> On Fri, 02 Mar 2012 09:51:27 +0400
>> Konstantin Khlebnikov<khlebnikov@openvz.org> wrote:
>>
>>> KAMEZAWA Hiroyuki wrote:
>>>> On Wed, 29 Feb 2012 13:15:47 +0400
>>>> Konstantin Khlebnikov<khlebnikov@openvz.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@openvz.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;

Code lines are cheap, if code is clear.
I already sent [PATCH 3/7 v2] in reply to this patch.

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