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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 86DC3C64E7D for ; Sun, 29 Nov 2020 11:29:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A87212076A for ; Sun, 29 Nov 2020 11:29:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=natalenko.name header.i=@natalenko.name header.b="pWeETqbI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A87212076A Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=natalenko.name Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CA8606B005C; Sun, 29 Nov 2020 06:29:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C59046B005D; Sun, 29 Nov 2020 06:29:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B6EB26B0068; Sun, 29 Nov 2020 06:29:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0043.hostedemail.com [216.40.44.43]) by kanga.kvack.org (Postfix) with ESMTP id 9E0126B005C for ; Sun, 29 Nov 2020 06:29:26 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 5C499363E for ; Sun, 29 Nov 2020 11:29:26 +0000 (UTC) X-FDA: 77537235132.14.quill75_440e7b027398 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id 3DD7118229837 for ; Sun, 29 Nov 2020 11:29:26 +0000 (UTC) X-HE-Tag: quill75_440e7b027398 X-Filterd-Recvd-Size: 3778 Received: from vulcan.natalenko.name (vulcan.natalenko.name [104.207.131.136]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Sun, 29 Nov 2020 11:29:24 +0000 (UTC) Received: from localhost (home.natalenko.name [151.237.229.131]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by vulcan.natalenko.name (Postfix) with ESMTPSA id 197798B3B96; Sun, 29 Nov 2020 12:29:23 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=natalenko.name; s=dkim-20170712; t=1606649363; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=sF8XCvJqTkyy+3B7MTwnlGdMjCa6TL1aBnFxb7P7jys=; b=pWeETqbI5g8QRDYwiq37mZkwL4JUnHA2rLrJ52YB8p5uBwt/wVaHqFaLTIC0MoO0cUWZvZ v7QjUoHaVuQXkzomeVl87agmzkzVM2xJNm2BJXMDJ+Z9MFQYxSNBRLnQACvFgUbBwqEqct h/E/TQpofgl189N0U6cY3X59Umx4l58= Date: Sun, 29 Nov 2020 12:29:22 +0100 From: Oleksandr Natalenko To: Mike Galbraith Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Sebastian Andrzej Siewior , Steven Rostedt , Thomas Gleixner , linux-rt-users@vger.kernel.org Subject: Re: scheduling while atomic in z3fold Message-ID: <20201129112922.db53kmtpu76xxukj@spock.localdomain> References: <20201128140523.ovmqon5fjetvpby4@spock.localdomain> <20201128140924.iyqr2h52z2olt6zb@spock.localdomain> <20201128142723.zik6d5skvt3uwu5f@spock.localdomain> <15171df044b167351e7f6a688aabd71bade9ae2a.camel@gmx.de> <79ee43026efe5aaa560953ea8fe29a826ac4e855.camel@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Nov 29, 2020 at 11:56:55AM +0100, Mike Galbraith wrote: > On Sun, 2020-11-29 at 10:21 +0100, Mike Galbraith wrote: > > On Sun, 2020-11-29 at 08:48 +0100, Mike Galbraith wrote: > > > On Sun, 2020-11-29 at 07:41 +0100, Mike Galbraith wrote: > > > > On Sat, 2020-11-28 at 15:27 +0100, Oleksandr Natalenko wrote: > > > > > > > > > > > > Shouldn't the list manipulation be protected with > > > > > > > local_lock+this_cpu_ptr instead of get_cpu_ptr+spin_lock? > > > > > > > > > > Totally untested: > > > > > > > > Hrm, the thing doesn't seem to care deeply about preemption being > > > > disabled, so adding another lock may be overkill. It looks like you > > > > could get the job done via migrate_disable()+this_cpu_ptr(). > > > > > > There is however an ever so tiny chance that I'm wrong about that :) > > > > Or not, your local_lock+this_cpu_ptr version exploded too. > > > > Perhaps there's a bit of non-rt related racy racy going on in zswap > > thingy that makes swap an even less wonderful idea for RT than usual. > > Raciness seems to be restricted to pool compressor. "zbud" seems to be > solid, virgin "zsmalloc" explodes, as does "z3fold" regardless which of > us puts his grubby fingerprints on it. > > Exploding compressors survived zero runs of runltp -f mm, I declared > zbud to be at least kinda sorta stable after box survived five runs. Ummm so do compressors explode under non-rt kernel in your tests as well, or it is just -rt that triggers this? I've never seen that on both -rt and non-rt, thus asking. -- Oleksandr Natalenko (post-factum)