From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753932AbdCBEPL (ORCPT ); Wed, 1 Mar 2017 23:15:11 -0500 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:48983 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753576AbdCBEPJ (ORCPT ); Wed, 1 Mar 2017 23:15:09 -0500 X-Original-SENDERIP: 156.147.1.127 X-Original-MAILFROM: sangwoo2.park@lge.com X-Original-SENDERIP: 165.244.249.26 X-Original-MAILFROM: sangwoo2.park@lge.com X-Original-SENDERIP: 10.168.178.132 X-Original-MAILFROM: sangwoo2.park@lge.com From: Sangwoo To: , CC: , , Sangwoo Subject: [PATCH] zram: reduce load operation in page_same_filled Date: Thu, 2 Mar 2017 13:15:04 +0900 Message-ID: <1488428104-7257-1-git-send-email-sangwoo2.park@lge.com> X-Mailer: git-send-email 2.6.2 X-MIMETrack: Itemize by SMTP Server on LGEKRMHUB03/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2017/03/02 13:15:05, Serialize by Router on LGEKRMHUB03/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2017/03/02 13:15:05, Serialize complete at 2017/03/02 13:15:05 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In page_same_filled function, all elements in the page is compared with next index value. The current comparison routine compares the (i)th and (i+1)th values of the page. In this case, two load operaions occur for each comparison. But if we store first value of the page stores at 'val' variable and using it to compare with others, the load opearation is reduced. It reduce load operation per page by up to 64times. Signed-off-by: Sangwoo --- drivers/block/zram/zram_drv.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index e27d89a..87581d1 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -177,15 +177,17 @@ static bool page_same_filled(void *ptr, unsigned long *element) { unsigned int pos; unsigned long *page; + unsigned long val; page = (unsigned long *)ptr; + val = page[0]; - for (pos = 0; pos < PAGE_SIZE / sizeof(*page) - 1; pos++) { - if (page[pos] != page[pos + 1]) + for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) { + if (val != page[pos]) return false; } - *element = page[pos]; + *element = val; return true; } -- 2.6.2