| Message ID | 20230808020555.658430-1-linmiaohe@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/page_alloc: remove unneeded current_order check | expand |
On Tue, 8 Aug 2023 10:05:55 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote: > current_order is guaranteed to '>=' min_order while min_order always '>=' > order. So current_order must be '>=' order. > > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> > --- > mm/page_alloc.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 96b7c1a7d1f2..d37ec87515d0 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2072,8 +2072,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype, > * allocation falls back into a different pageblock than this > * one, it won't cause permanent fragmentation. > */ > - if (!can_steal && start_migratetype == MIGRATE_MOVABLE > - && current_order > order) > + if (!can_steal && start_migratetype == MIGRATE_MOVABLE) > goto find_smallest; Hi, if my analysis is correct, min_order can be initialized to the value of order before the loop begins. In that case, in the last loop iteration, current_order will be equal to min_order and also to order. The condition 'current_order > order' will evaluate to false, and the 'if' block should not be executed? Hugo.
On 2023/8/8 20:16, Hugo Villeneuve wrote: > On Tue, 8 Aug 2023 10:05:55 +0800 > Miaohe Lin <linmiaohe@huawei.com> wrote: > >> current_order is guaranteed to '>=' min_order while min_order always '>=' >> order. So current_order must be '>=' order. >> >> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> >> --- >> mm/page_alloc.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 96b7c1a7d1f2..d37ec87515d0 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -2072,8 +2072,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype, >> * allocation falls back into a different pageblock than this >> * one, it won't cause permanent fragmentation. >> */ >> - if (!can_steal && start_migratetype == MIGRATE_MOVABLE >> - && current_order > order) >> + if (!can_steal && start_migratetype == MIGRATE_MOVABLE) >> goto find_smallest; > > Hi, > if my analysis is correct, min_order can be initialized to the value of > order before the loop begins. > > In that case, in the last loop iteration, current_order will be > equal to min_order and also to order. The condition 'current_order > > order' will evaluate to false, and the 'if' block should not be > executed? Oh, that's my mistake. Thanks for pointing this out. Will drop this patch. Thanks!
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 96b7c1a7d1f2..d37ec87515d0 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2072,8 +2072,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype, * allocation falls back into a different pageblock than this * one, it won't cause permanent fragmentation. */ - if (!can_steal && start_migratetype == MIGRATE_MOVABLE - && current_order > order) + if (!can_steal && start_migratetype == MIGRATE_MOVABLE) goto find_smallest; goto do_steal;
current_order is guaranteed to '>=' min_order while min_order always '>=' order. So current_order must be '>=' order. Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- mm/page_alloc.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)