From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f182.google.com (mail-ob0-f182.google.com [209.85.214.182]) by kanga.kvack.org (Postfix) with ESMTP id A76536B006E for ; Fri, 21 Nov 2014 00:33:27 -0500 (EST) Received: by mail-ob0-f182.google.com with SMTP id m8so3474723obr.13 for ; Thu, 20 Nov 2014 21:33:27 -0800 (PST) Received: from mail-ob0-x22a.google.com (mail-ob0-x22a.google.com. [2607:f8b0:4003:c01::22a]) by mx.google.com with ESMTPS id j8si2892275obk.3.2014.11.20.21.33.26 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 20 Nov 2014 21:33:26 -0800 (PST) Received: by mail-ob0-f170.google.com with SMTP id wp18so3504889obc.1 for ; Thu, 20 Nov 2014 21:33:26 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20141121035442.GB10123@bbox> References: <1416489716-9967-1-git-send-email-opensource.ganesh@gmail.com> <20141121035442.GB10123@bbox> Date: Fri, 21 Nov 2014 13:33:26 +0800 Message-ID: Subject: Re: [RFC PATCH] mm/zsmalloc: remove unnecessary check From: Ganesh Mahendran Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Nitin Gupta , Joonsoo Kim , Linux-MM , linux-kernel Hello 2014-11-21 11:54 GMT+08:00 Minchan Kim : > 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 >> --- >> 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: email@kvack.org > > -- > 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: email@kvack.org