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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CBE8EC433EF for ; Thu, 13 Jan 2022 16:42:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236829AbiAMQmI (ORCPT ); Thu, 13 Jan 2022 11:42:08 -0500 Received: from foss.arm.com ([217.140.110.172]:48516 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231919AbiAMQmE (ORCPT ); Thu, 13 Jan 2022 11:42:04 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3223E106F; Thu, 13 Jan 2022 08:42:04 -0800 (PST) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.196.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ED6483F774; Thu, 13 Jan 2022 08:42:02 -0800 (PST) From: Valentin Schneider To: Josef Bacik Cc: Thorsten Leemhuis , peterz@infradead.org, vincent.guittot@linaro.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, guro@fb.com, clm@fb.com Subject: Re: [REGRESSION] 5-10% increase in IO latencies with nohz balance patch In-Reply-To: References: <87bl22byq2.mognet@arm.com> <878rx6bia5.mognet@arm.com> <87wnklaoa8.mognet@arm.com> <87lf0y9i8x.mognet@arm.com> <87v8zx8zia.mognet@arm.com> <99452126-661e-9a0c-6b51-d345ed0f76ee@leemhuis.info> <87tuf07hdk.mognet@arm.com> Date: Thu, 13 Jan 2022 16:41:57 +0000 Message-ID: <87k0f37fl6.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/01/22 11:16, Josef Bacik wrote: > On Wed, Dec 22, 2021 at 04:07:35PM +0000, Valentin Schneider wrote: >> >> Hi, >> >> On 22/12/21 13:42, Thorsten Leemhuis wrote: >> > What's the status here? Just wondering, because there hasn't been any >> > activity in this thread since 11 days and the festive season is upon us. >> > >> > Was the discussion moved elsewhere? Or is this still a mystery? And if >> > it is: how bad is it, does it need to be fixed before Linus releases 5.16? >> > >> >> I got to the end of bisect #3 yesterday, the incriminated commit doesn't >> seem to make much sense but I've just re-tested it and there is a clear >> regression between that commit and its parent (unlike bisect #1 and #2): >> >> 2127d22509aec3a83dffb2a3c736df7ba747a7ce mm, slub: fix two bugs in slab_debug_trace_open() >> write_clat_ns_p99 195395.92 199638.20 4797.01 2.17% >> write_iops 17305.79 17188.24 250.66 -0.68% >> >> write_clat_ns_p99 195543.84 199996.70 5122.88 2.28% >> write_iops 17300.61 17241.86 251.56 -0.34% >> >> write_clat_ns_p99 195543.84 200724.48 5122.88 2.65% >> write_iops 17300.61 17246.63 251.56 -0.31% >> >> write_clat_ns_p99 195543.84 200445.41 5122.88 2.51% >> write_iops 17300.61 17215.47 251.56 -0.49% >> >> 6d2aec9e123bb9c49cb5c7fc654f25f81e688e8c mm/mempolicy: do not allow illegal MPOL_F_NUMA_BALANCING | MPOL_LOCAL in mbind() >> write_clat_ns_p99 195395.92 197942.30 4797.01 1.30% >> write_iops 17305.79 17246.56 250.66 -0.34% >> >> write_clat_ns_p99 195543.84 196183.92 5122.88 0.33% >> write_iops 17300.61 17310.33 251.56 0.06% >> >> write_clat_ns_p99 195543.84 196990.71 5122.88 0.74% >> write_iops 17300.61 17346.32 251.56 0.26% >> >> write_clat_ns_p99 195543.84 196362.24 5122.88 0.42% >> write_iops 17300.61 17315.71 251.56 0.09% >> >> It's pure debug stuff and AFAICT is a correct fix... >> @Josef, could you test that on your side? > > Sorry, holidays and all that. I see 0 difference between the two commits, and > no regression from baseline. It'll take me a few days to recover from the > holidays, but I'll put some more effort into actively debugging wtf is going on > here on my side since we're all having trouble pinning down what's going > on. Humph, that's unfortunate... I just came back from my holidays, so I'll be untangling my inbox for the next few days. Do keep us posted! > Thanks, > > Josef