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Date: Fri, 21 Nov 2014 13:33:26 +0800 From: Ganesh Mahendran <opensource.ganesh@...il.com> To: Minchan Kim <minchan@...nel.org> Cc: Nitin Gupta <ngupta@...are.org>, Joonsoo Kim <iamjoonsoo.kim@....com>, Linux-MM <linux-mm@...ck.org>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check Hello 2014-11-21 11:54 GMT+08:00 Minchan Kim <minchan@...nel.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@...il.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@...ck.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a> > > -- > Kind regards, > Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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