From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05A0EC43331 for ; Mon, 30 Mar 2020 12:09:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D758720716 for ; Mon, 30 Mar 2020 12:09:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730119AbgC3MJn (ORCPT ); Mon, 30 Mar 2020 08:09:43 -0400 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:51715 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729627AbgC3MJm (ORCPT ); Mon, 30 Mar 2020 08:09:42 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04397;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0Tu2RGTX_1585570174; Received: from JosephdeMacBook-Pro.local(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0Tu2RGTX_1585570174) by smtp.aliyun-inc.com(127.0.0.1); Mon, 30 Mar 2020 20:09:34 +0800 Subject: Re: [RFC PATCH v1 29/50] fs/ocfs2/journal: Use prandom_u32() and not /dev/random for timeout To: George Spelvin , linux-kernel@vger.kernel.org Cc: Mark Fasheh , Joel Becker , ocfs2-devel@oss.oracle.com References: <202003281643.02SGhIOY022599@sdf.org> From: Joseph Qi Message-ID: <016c2bdc-68eb-245f-2292-d00d0d8e45a5@linux.alibaba.com> Date: Mon, 30 Mar 2020 20:09:33 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <202003281643.02SGhIOY022599@sdf.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sorry for the late reply since I might miss this mail. On 2019/3/21 11:07, George Spelvin wrote: > get_random_bytes() is expensive crypto-quality random numbers. > If we're just doing random backoff, prandom_u32() is plenty. > > (Not to mention fetching 8 bytes of seed material only to > reduce it modulo 5000 is a huge waste.) > > Also, convert timeouts to jiffies at compile time; convert > milliseconds to jiffies before picking a random number in the > range to take advantage of compile-time constant folding. > > Signed-off-by: George Spelvin > Cc: Mark Fasheh > Cc: Joel Becker > Cc: Joseph Qi > Cc: ocfs2-devel@oss.oracle.com > --- > fs/ocfs2/journal.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c > index 68ba354cf3610..939a12e57fa8b 100644 > --- a/fs/ocfs2/journal.c > +++ b/fs/ocfs2/journal.c > @@ -1884,11 +1884,8 @@ int ocfs2_mark_dead_nodes(struct ocfs2_super *osb) > */ > static inline unsigned long ocfs2_orphan_scan_timeout(void) > { > - unsigned long time; > - > - get_random_bytes(&time, sizeof(time)); > - time = ORPHAN_SCAN_SCHEDULE_TIMEOUT + (time % 5000); > - return msecs_to_jiffies(time); > + return msecs_to_jiffies(ORPHAN_SCAN_SCHEDULE_TIMEOUT) + > + prandom_u32_max(5 * HZ); Seems better include the prandom_u32_max() into msecs_to_jiffies()? Thanks, Joseph > } > > /* >