* [RFC PATCH] mm/zsmalloc: remove unnecessary check @ 2014-11-20 13:21 Mahendran Ganesh 2014-11-21 3:54 ` Minchan Kim 0 siblings, 1 reply; 7+ messages in thread From: Mahendran Ganesh @ 2014-11-20 13:21 UTC (permalink / raw) To: minchan, ngupta, iamjoonsoo.kim; +Cc: linux-mm, linux-kernel, Mahendran Ganesh ZS_SIZE_CLASSES is calc by: ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1) So when i is in [0, ZS_SIZE_CLASSES - 1), the size: size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA will not be greater than ZS_MAX_ALLOC_SIZE This patch removes the unnecessary check. Signed-off-by: Mahendran Ganesh <opensource.ganesh@gmail.com> --- mm/zsmalloc.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index b3b57ef..f2279e2 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -973,8 +973,6 @@ struct zs_pool *zs_create_pool(gfp_t flags) struct size_class *prev_class; size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA; - if (size > ZS_MAX_ALLOC_SIZE) - size = ZS_MAX_ALLOC_SIZE; pages_per_zspage = get_pages_per_zspage(size); /* -- 1.7.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check 2014-11-20 13:21 [RFC PATCH] mm/zsmalloc: remove unnecessary check Mahendran Ganesh @ 2014-11-21 3:54 ` Minchan Kim 2014-11-21 5:33 ` Ganesh Mahendran 0 siblings, 1 reply; 7+ messages in thread From: Minchan Kim @ 2014-11-21 3:54 UTC (permalink / raw) To: Mahendran Ganesh; +Cc: ngupta, iamjoonsoo.kim, linux-mm, linux-kernel On Thu, Nov 20, 2014 at 09:21:56PM +0800, Mahendran Ganesh wrote: > ZS_SIZE_CLASSES is calc by: > ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1) > > So when i is in [0, ZS_SIZE_CLASSES - 1), the size: > size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA > will not be greater than ZS_MAX_ALLOC_SIZE > > This patch removes the unnecessary check. It depends on ZS_MIN_ALLOC_SIZE. For example, we would change min to 8 but MAX is still 4096. ZS_SIZE_CLASSES is (4096 - 8) / 16 + 1 = 256 so 8 + 255 * 16 = 4088, which exceeds the max. > > Signed-off-by: Mahendran Ganesh <opensource.ganesh@gmail.com> > --- > mm/zsmalloc.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index b3b57ef..f2279e2 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -973,8 +973,6 @@ struct zs_pool *zs_create_pool(gfp_t flags) > struct size_class *prev_class; > > size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA; > - if (size > ZS_MAX_ALLOC_SIZE) > - size = ZS_MAX_ALLOC_SIZE; > pages_per_zspage = get_pages_per_zspage(size); > > /* > -- > 1.7.9.5 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check 2014-11-21 3:54 ` Minchan Kim @ 2014-11-21 5:33 ` Ganesh Mahendran 2014-11-21 6:48 ` Minchan Kim 0 siblings, 1 reply; 7+ messages in thread From: Ganesh Mahendran @ 2014-11-21 5:33 UTC (permalink / raw) To: Minchan Kim; +Cc: Nitin Gupta, Joonsoo Kim, Linux-MM, linux-kernel Hello 2014-11-21 11:54 GMT+08:00 Minchan Kim <minchan@kernel.org>: > On Thu, Nov 20, 2014 at 09:21:56PM +0800, Mahendran Ganesh wrote: >> ZS_SIZE_CLASSES is calc by: >> ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1) >> >> So when i is in [0, ZS_SIZE_CLASSES - 1), the size: >> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA >> will not be greater than ZS_MAX_ALLOC_SIZE >> >> This patch removes the unnecessary check. > > It depends on ZS_MIN_ALLOC_SIZE. > For example, we would change min to 8 but MAX is still 4096. > ZS_SIZE_CLASSES is (4096 - 8) / 16 + 1 = 256 so 8 + 255 * 16 = 4088, > which exceeds the max. Here, 4088 is less than MAX(4096). ZS_SIZE_CLASSES = (MAX - MIN) / Delta + 1 So, I think the value of MIN + (ZS_SIZE_CLASSES - 1) * Delta = MIN + ((MAX - MIN) / Delta) * Delta = MAX will not exceed the MAX Thanks. > >> >> Signed-off-by: Mahendran Ganesh <opensource.ganesh@gmail.com> >> --- >> mm/zsmalloc.c | 2 -- >> 1 file changed, 2 deletions(-) >> >> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c >> index b3b57ef..f2279e2 100644 >> --- a/mm/zsmalloc.c >> +++ b/mm/zsmalloc.c >> @@ -973,8 +973,6 @@ struct zs_pool *zs_create_pool(gfp_t flags) >> struct size_class *prev_class; >> >> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA; >> - if (size > ZS_MAX_ALLOC_SIZE) >> - size = ZS_MAX_ALLOC_SIZE; >> pages_per_zspage = get_pages_per_zspage(size); >> >> /* >> -- >> 1.7.9.5 >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> > > -- > Kind regards, > Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check 2014-11-21 5:33 ` Ganesh Mahendran @ 2014-11-21 6:48 ` Minchan Kim 2014-11-21 10:32 ` Minchan Kim 0 siblings, 1 reply; 7+ messages in thread From: Minchan Kim @ 2014-11-21 6:48 UTC (permalink / raw) To: Ganesh Mahendran; +Cc: Nitin Gupta, Joonsoo Kim, Linux-MM, linux-kernel On Fri, Nov 21, 2014 at 01:33:26PM +0800, Ganesh Mahendran wrote: > Hello > > 2014-11-21 11:54 GMT+08:00 Minchan Kim <minchan@kernel.org>: > > On Thu, Nov 20, 2014 at 09:21:56PM +0800, Mahendran Ganesh wrote: > >> ZS_SIZE_CLASSES is calc by: > >> ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1) > >> > >> So when i is in [0, ZS_SIZE_CLASSES - 1), the size: > >> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA > >> will not be greater than ZS_MAX_ALLOC_SIZE > >> > >> This patch removes the unnecessary check. > > > > It depends on ZS_MIN_ALLOC_SIZE. > > For example, we would change min to 8 but MAX is still 4096. > > ZS_SIZE_CLASSES is (4096 - 8) / 16 + 1 = 256 so 8 + 255 * 16 = 4088, > > which exceeds the max. > Here, 4088 is less than MAX(4096). > > ZS_SIZE_CLASSES = (MAX - MIN) / Delta + 1 > So, I think the value of > MIN + (ZS_SIZE_CLASSES - 1) * Delta = > MIN + ((MAX - MIN) / Delta) * Delta = > MAX > will not exceed the MAX You're right. It was complext math for me. I should go back to elementary school. Thanks! Acked-by: Minchan Kim <minchan@kernel.org> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check 2014-11-21 6:48 ` Minchan Kim @ 2014-11-21 10:32 ` Minchan Kim 2014-11-21 14:56 ` Ganesh Mahendran 0 siblings, 1 reply; 7+ messages in thread From: Minchan Kim @ 2014-11-21 10:32 UTC (permalink / raw) To: Ganesh Mahendran; +Cc: Nitin Gupta, Joonsoo Kim, Linux-MM, linux-kernel On Fri, Nov 21, 2014 at 06:48:49AM +0000, Minchan Kim wrote: > On Fri, Nov 21, 2014 at 01:33:26PM +0800, Ganesh Mahendran wrote: > > Hello > > > > 2014-11-21 11:54 GMT+08:00 Minchan Kim <minchan@kernel.org>: > > > On Thu, Nov 20, 2014 at 09:21:56PM +0800, Mahendran Ganesh wrote: > > >> ZS_SIZE_CLASSES is calc by: > > >> ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1) > > >> > > >> So when i is in [0, ZS_SIZE_CLASSES - 1), the size: > > >> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA > > >> will not be greater than ZS_MAX_ALLOC_SIZE > > >> > > >> This patch removes the unnecessary check. > > > > > > It depends on ZS_MIN_ALLOC_SIZE. > > > For example, we would change min to 8 but MAX is still 4096. > > > ZS_SIZE_CLASSES is (4096 - 8) / 16 + 1 = 256 so 8 + 255 * 16 = 4088, > > > which exceeds the max. > > Here, 4088 is less than MAX(4096). > > > > ZS_SIZE_CLASSES = (MAX - MIN) / Delta + 1 > > So, I think the value of > > MIN + (ZS_SIZE_CLASSES - 1) * Delta = > > MIN + ((MAX - MIN) / Delta) * Delta = > > MAX > > will not exceed the MAX > > You're right. It was complext math for me. > I should go back to elementary school. > > Thanks! > > Acked-by: Minchan Kim <minchan@kernel.org> I catch a nasty cold but above my poor math makes me think more. ZS_SIZE_CLASSES is broken. In above my example, current code cannot allocate 4096 size class so we should correct ZS_SIZE_CLASSES at first. zs_size_classes = zs_max - zs_min / delta + 1; if ((zs_max - zs_min) % delta) zs_size_classes += 1; Then, we need to code piece you removed. As well, we need to fix below. - area->vm_buf = (char *)__get_free_page(GFP_KERNEL); + area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE); Hope I am sane in this time :( -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check 2014-11-21 10:32 ` Minchan Kim @ 2014-11-21 14:56 ` Ganesh Mahendran 2014-11-24 7:55 ` Minchan Kim 0 siblings, 1 reply; 7+ messages in thread From: Ganesh Mahendran @ 2014-11-21 14:56 UTC (permalink / raw) To: Minchan Kim; +Cc: Nitin Gupta, Joonsoo Kim, Linux-MM, linux-kernel Hello Minchan 2014-11-21 18:32 GMT+08:00 Minchan Kim <minchan@kernel.org>: > On Fri, Nov 21, 2014 at 06:48:49AM +0000, Minchan Kim wrote: >> On Fri, Nov 21, 2014 at 01:33:26PM +0800, Ganesh Mahendran wrote: >> > Hello >> > >> > 2014-11-21 11:54 GMT+08:00 Minchan Kim <minchan@kernel.org>: >> > > On Thu, Nov 20, 2014 at 09:21:56PM +0800, Mahendran Ganesh wrote: >> > >> ZS_SIZE_CLASSES is calc by: >> > >> ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1) >> > >> >> > >> So when i is in [0, ZS_SIZE_CLASSES - 1), the size: >> > >> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA >> > >> will not be greater than ZS_MAX_ALLOC_SIZE >> > >> >> > >> This patch removes the unnecessary check. >> > > >> > > It depends on ZS_MIN_ALLOC_SIZE. >> > > For example, we would change min to 8 but MAX is still 4096. >> > > ZS_SIZE_CLASSES is (4096 - 8) / 16 + 1 = 256 so 8 + 255 * 16 = 4088, >> > > which exceeds the max. >> > Here, 4088 is less than MAX(4096). >> > >> > ZS_SIZE_CLASSES = (MAX - MIN) / Delta + 1 >> > So, I think the value of >> > MIN + (ZS_SIZE_CLASSES - 1) * Delta = >> > MIN + ((MAX - MIN) / Delta) * Delta = >> > MAX >> > will not exceed the MAX >> >> You're right. It was complext math for me. >> I should go back to elementary school. >> >> Thanks! >> >> Acked-by: Minchan Kim <minchan@kernel.org> > > I catch a nasty cold but above my poor math makes me think more. > ZS_SIZE_CLASSES is broken. In above my example, current code cannot > allocate 4096 size class so we should correct ZS_SIZE_CLASSES > at first. > > zs_size_classes = zs_max - zs_min / delta + 1; > if ((zs_max - zs_min) % delta) > zs_size_classes += 1; Yes, you are right. When the zs_min is less than delta, we can not allocate PAGE_SIZE size class. > > Then, we need to code piece you removed. > As well, we need to fix below. > > - area->vm_buf = (char *)__get_free_page(GFP_KERNEL); > + area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE); If our purpose is to allocate the max obj size as len of PAGE_SIZE, we do not need to change this line. Since the ZS_MAX_ALLOC_SIZE will always be PAGE_SIZE Thanks. > > Hope I am sane in this time :( -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check 2014-11-21 14:56 ` Ganesh Mahendran @ 2014-11-24 7:55 ` Minchan Kim 0 siblings, 0 replies; 7+ messages in thread From: Minchan Kim @ 2014-11-24 7:55 UTC (permalink / raw) To: Ganesh Mahendran; +Cc: Nitin Gupta, Joonsoo Kim, Linux-MM, linux-kernel Hello Ganesh, On Fri, Nov 21, 2014 at 10:56:10PM +0800, Ganesh Mahendran wrote: > Hello Minchan > > 2014-11-21 18:32 GMT+08:00 Minchan Kim <minchan@kernel.org>: > > On Fri, Nov 21, 2014 at 06:48:49AM +0000, Minchan Kim wrote: > >> On Fri, Nov 21, 2014 at 01:33:26PM +0800, Ganesh Mahendran wrote: > >> > Hello > >> > > >> > 2014-11-21 11:54 GMT+08:00 Minchan Kim <minchan@kernel.org>: > >> > > On Thu, Nov 20, 2014 at 09:21:56PM +0800, Mahendran Ganesh wrote: > >> > >> ZS_SIZE_CLASSES is calc by: > >> > >> ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1) > >> > >> > >> > >> So when i is in [0, ZS_SIZE_CLASSES - 1), the size: > >> > >> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA > >> > >> will not be greater than ZS_MAX_ALLOC_SIZE > >> > >> > >> > >> This patch removes the unnecessary check. > >> > > > >> > > It depends on ZS_MIN_ALLOC_SIZE. > >> > > For example, we would change min to 8 but MAX is still 4096. > >> > > ZS_SIZE_CLASSES is (4096 - 8) / 16 + 1 = 256 so 8 + 255 * 16 = 4088, > >> > > which exceeds the max. > >> > Here, 4088 is less than MAX(4096). > >> > > >> > ZS_SIZE_CLASSES = (MAX - MIN) / Delta + 1 > >> > So, I think the value of > >> > MIN + (ZS_SIZE_CLASSES - 1) * Delta = > >> > MIN + ((MAX - MIN) / Delta) * Delta = > >> > MAX > >> > will not exceed the MAX > >> > >> You're right. It was complext math for me. > >> I should go back to elementary school. > >> > >> Thanks! > >> > >> Acked-by: Minchan Kim <minchan@kernel.org> > > > > I catch a nasty cold but above my poor math makes me think more. > > ZS_SIZE_CLASSES is broken. In above my example, current code cannot > > allocate 4096 size class so we should correct ZS_SIZE_CLASSES > > at first. > > > > zs_size_classes = zs_max - zs_min / delta + 1; > > if ((zs_max - zs_min) % delta) > > zs_size_classes += 1; > Yes, you are right. > When the zs_min is less than delta, we can not allocate PAGE_SIZE size class. > > > > > Then, we need to code piece you removed. > > As well, we need to fix below. > > > > - area->vm_buf = (char *)__get_free_page(GFP_KERNEL); > > + area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE); > If our purpose is to allocate the max obj size as len of PAGE_SIZE, we > do not need to > change this line. Since the ZS_MAX_ALLOC_SIZE will always be PAGE_SIZE No, please don't assume ZS_MAX_ALLOC_SIZE is PAGE_SIZE forever. Some reason could make buffer larger than PAGE_SIZE. For example, we might put allocator's metadata into each object's head/tail. -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-11-24 7:55 UTC | newest] Thread overview: 7+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2014-11-20 13:21 [RFC PATCH] mm/zsmalloc: remove unnecessary check Mahendran Ganesh 2014-11-21 3:54 ` Minchan Kim 2014-11-21 5:33 ` Ganesh Mahendran 2014-11-21 6:48 ` Minchan Kim 2014-11-21 10:32 ` Minchan Kim 2014-11-21 14:56 ` Ganesh Mahendran 2014-11-24 7:55 ` Minchan Kim
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