Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751796AbaKUFWX (ORCPT ); Fri, 21 Nov 2014 00:22:23 -0500 Received: from mail-ob0-f177.google.com ([209.85.214.177]:41645 "EHLO mail-ob0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750715AbaKUFWW (ORCPT ); Fri, 21 Nov 2014 00:22:22 -0500 MIME-Version: 1.0 In-Reply-To: References: <1416488913-9691-1-git-send-email-opensource.ganesh@gmail.com> Date: Fri, 21 Nov 2014 13:22:21 +0800 Message-ID: Subject: Re: [PATCH] mm/zsmalloc: avoid duplicate assignment of prev_class From: Ganesh Mahendran To: Dan Streetman Cc: Minchan Kim , Nitin Gupta , Joonsoo Kim , Linux-MM , linux-kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello 2014-11-21 11:22 GMT+08:00 Dan Streetman : > On Thu, Nov 20, 2014 at 8:08 AM, Mahendran Ganesh > wrote: >> In zs_create_pool(), prev_class is assigned (ZS_SIZE_CLASSES - 1) >> times. And the prev_class only references to the previous alloc >> size_class. So we do not need unnecessary assignement. >> >> This patch modifies *prev_class* to *prev_alloc_class*. And the >> *prev_alloc_class* will only be assigned when a new size_class >> structure is allocated. >> >> Signed-off-by: Mahendran Ganesh >> --- >> mm/zsmalloc.c | 9 +++++---- >> 1 file changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c >> index b3b57ef..ac2b396 100644 >> --- a/mm/zsmalloc.c >> +++ b/mm/zsmalloc.c >> @@ -970,7 +970,7 @@ struct zs_pool *zs_create_pool(gfp_t flags) >> int size; >> int pages_per_zspage; >> struct size_class *class; >> - struct size_class *prev_class; >> + struct size_class *uninitialized_var(prev_alloc_class); > > + struct size_class *prev_class = NULL; > > Use the fact it's unset below, so set it to NULL here Yes, You are right. I will change it in next resend. Thanks for your review. > >> >> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA; >> if (size > ZS_MAX_ALLOC_SIZE) >> @@ -987,9 +987,8 @@ struct zs_pool *zs_create_pool(gfp_t flags) >> * previous size_class if possible. >> */ >> if (i < ZS_SIZE_CLASSES - 1) { >> - prev_class = pool->size_class[i + 1]; >> - if (can_merge(prev_class, size, pages_per_zspage)) { >> - pool->size_class[i] = prev_class; >> + if (can_merge(prev_alloc_class, size, pages_per_zspage)) { >> + pool->size_class[i] = prev_alloc_class; > > simplify more, we can check if this is the first iteration by looking > at prev_class, e.g.: > > if (prev_class) { > if (can_merge(prev_class, size, pages_per_zspage)) { > pool->size_class[i] = prev_class; > > >> continue; >> } >> } >> @@ -1003,6 +1002,8 @@ struct zs_pool *zs_create_pool(gfp_t flags) >> class->pages_per_zspage = pages_per_zspage; >> spin_lock_init(&class->lock); >> pool->size_class[i] = class; >> + >> + prev_alloc_class = class; >> } >> >> pool->flags = flags; >> -- >> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/