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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 3A29AC10F27 for ; Mon, 9 Mar 2020 08:27:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14D842087F for ; Mon, 9 Mar 2020 08:27:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726449AbgCII1E (ORCPT ); Mon, 9 Mar 2020 04:27:04 -0400 Received: from mga17.intel.com ([192.55.52.151]:63271 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726215AbgCII1E (ORCPT ); Mon, 9 Mar 2020 04:27:04 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Mar 2020 01:27:03 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,532,1574150400"; d="scan'208";a="230851565" Received: from shao2-debian.sh.intel.com (HELO localhost) ([10.239.13.3]) by orsmga007.jf.intel.com with ESMTP; 09 Mar 2020 01:27:00 -0700 Date: Mon, 9 Mar 2020 16:26:49 +0800 From: kernel test robot To: Thomas Gleixner Cc: Linus Torvalds , Peter Zijlstra , Jann Horn , LKML , x86-ml , Ingo Molnar , Borislav Petkov , lkp@lists.01.org Subject: Re: [futex] 8019ad13ef: will-it-scale.per_process_ops -97.8% regression Message-ID: <20200309082649.GT5972@shao2-debian> References: <20200308140200.GO5972@shao2-debian> <87h7yy90ve.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87h7yy90ve.fsf@nanos.tec.linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 08, 2020 at 07:07:17PM +0100, Thomas Gleixner wrote: > Linus Torvalds writes: > > > [ Just a re-send without html crud that makes all the lists unhappy. > > I'm still on the road, the flight I was supposed to be on yesterday > > got cancelled.. ] > > > > I do note that the futex hashing seems to be broken by that commit. Or > > at least it's questionable. It keeps hashing on "both.word", and > > doesn't use the u64 field at all for hashing. > > > > Maybe I'm mis-reading it - I didn't apply the patch, I just looked at > > the patch and my source base separately. > > > > But the 98% regression sure says something went wrong ;) > > Right you are. The pointer needs to be the starting point as it moved > ahead of word, which means it starts at word and hashes word and > offset and an extra u32 beyond the end of the key. > > Thanks, > > tglx > ---- > diff --git a/kernel/futex.c b/kernel/futex.c > index e14f7cd45dbd..9f3251349f65 100644 > --- a/kernel/futex.c > +++ b/kernel/futex.c > @@ -385,8 +385,8 @@ static inline int hb_waiters_pending(struct futex_hash_bucket *hb) > */ > static struct futex_hash_bucket *hash_futex(union futex_key *key) > { > - u32 hash = jhash2((u32*)&key->both.word, > - (sizeof(key->both.word)+sizeof(key->both.ptr))/4, > + u32 hash = jhash2((u32*)&key->both.ptr, > + (sizeof(key->both.ptr) + sizeof(key->both.word)) / 4, > key->both.offset); > return &futex_queues[hash & (futex_hashsize - 1)]; > } Hi Thomas, I have tested the above patch, and the patch can fix the regression. commit: v5.6-rc4 8019ad13ef ("futex: Fix inode life-time issue") 8eb641cbc3 ("the fix patch") v5.6-rc4 8019ad13ef7f64be44d4f892af 8eb641cbc397e3bbea2a9974e0 testcase/testparams/testbox ---------------- -------------------------- -------------------------- --------------------------- %stddev change %stddev change %stddev \ | \ | \ 1083510 -98% 23904 1078868 will-it-scale/performance-process-100%-futex2-ucode=0x2000065/lkp-skl-fpga01 1083510 -98% 23904 1078868 GEO-MEAN will-it-scale.per_process_ops Best Regards, Rong Chen