From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx108.postini.com [74.125.245.108]) by kanga.kvack.org (Postfix) with SMTP id 31D556B0083 for ; Thu, 3 May 2012 09:58:22 -0400 (EDT) Received: by qafl39 with SMTP id l39so305217qaf.9 for ; Thu, 03 May 2012 06:58:21 -0700 (PDT) Message-ID: <4FA28EFD.5070002@vflare.org> Date: Thu, 03 May 2012 09:58:21 -0400 From: Nitin Gupta MIME-Version: 1.0 Subject: Re: [PATCH 4/4] zsmalloc: zsmalloc: align cache line size References: <1336027242-372-1-git-send-email-minchan@kernel.org> <1336027242-372-4-git-send-email-minchan@kernel.org> In-Reply-To: <1336027242-372-4-git-send-email-minchan@kernel.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Greg Kroah-Hartman , Seth Jennings , Dan Magenheimer , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 5/3/12 2:40 AM, Minchan Kim wrote: > It's a overkill to align pool size with PAGE_SIZE to avoid > false-sharing. This patch aligns it with just cache line size. > > Signed-off-by: Minchan Kim > --- > drivers/staging/zsmalloc/zsmalloc-main.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c > index 51074fa..3991b03 100644 > --- a/drivers/staging/zsmalloc/zsmalloc-main.c > +++ b/drivers/staging/zsmalloc/zsmalloc-main.c > @@ -489,14 +489,14 @@ fail: > > struct zs_pool *zs_create_pool(const char *name, gfp_t flags) > { > - int i, error, ovhd_size; > + int i, error; > struct zs_pool *pool; > > if (!name) > return NULL; > > - ovhd_size = roundup(sizeof(*pool), PAGE_SIZE); > - pool = kzalloc(ovhd_size, GFP_KERNEL); > + pool = kzalloc(ALIGN(sizeof(*pool), cache_line_size()), > + GFP_KERNEL); a basic question: Is rounding off allocation size to cache_line_size enough to ensure that the object is cache-line-aligned? Isn't it possible that even though the object size is multiple of cache-line, it may still not be properly aligned and end up sharing cache line with some other read-mostly object? Thanks, Nitin > if (!pool) > return NULL; > -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org