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[209.85.219.169]) by smtp.gmail.com with ESMTPSA id f17-20020ac84651000000b0034305a91aaesm450009qto.83.2022.10.24.13.28.48 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Oct 2022 13:28:48 -0700 (PDT) Received: by mail-yb1-f169.google.com with SMTP id f205so12339071yba.2 for ; Mon, 24 Oct 2022 13:28:48 -0700 (PDT) X-Received: by 2002:a25:5389:0:b0:6bc:f12c:5d36 with SMTP id h131-20020a255389000000b006bcf12c5d36mr29953243ybb.184.1666643327656; Mon, 24 Oct 2022 13:28:47 -0700 (PDT) MIME-Version: 1.0 References: <6350a5f07bae2_6be12944c@dwillia2-xfh.jf.intel.com.notmuch> <6356f1f74678c_141929415@dwillia2-mobl3.amr.corp.intel.com.notmuch> In-Reply-To: <6356f1f74678c_141929415@dwillia2-mobl3.amr.corp.intel.com.notmuch> From: Linus Torvalds Date: Mon, 24 Oct 2022 13:28:31 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: writeback completion soft lockup BUG in folio_wake_bit() To: Dan Williams Cc: Matthew Wilcox , Brian Foster , Linux-MM , linux-fsdevel , linux-xfs , Hugh Dickins , jesus.a.arechiga.lopez@intel.com, tim.c.chen@linux.intel.com Content-Type: text/plain; charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666643331; a=rsa-sha256; cv=none; b=muGkTu0a+Rq81gPS3Rq27ASoY91dK4rn1+7z1CbPqaYd/HLH+BHbyFlJVkTL2GyLfIIkb0 fOmh4eCO2+w7/p9iaK3UaXRvFwRX7rOr01KAP167mhF665jh6BOLMAC0gdfhCfQ9XNfsDG syWvfpwmjicnjoZtXhNw1dkPPkoJbpM= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=NdKygZeW; spf=pass (imf23.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.160.174 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666643331; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=iSOcydxSXUj96NbU/Er00mnbcEfNU+h40IX+5ItHvVI=; b=tldLRPLkrsY3lF6c8lgUL0/O4JsUcu8Ceu+DpcTh5nVNxQ1hehYxNSbZ6DjxLvKTf6ZeKZ 9P9RNAo6Vs+fV5i5u3tME6PZDl/gRL2NbtFt+WhPjCoMjc/JDpUTob3Uw7IfEKHj9C6A9k xvixwVu97u6/lcY3b9i/NhsiidUOlJM= X-Rspam-User: X-Rspamd-Queue-Id: 10A50140020 Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=NdKygZeW; spf=pass (imf23.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.160.174 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-Stat-Signature: x51fhre77x5we3tujtiaqrypckk5gh3y X-Rspamd-Server: rspam03 X-HE-Tag: 1666643330-919550 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 Mon, Oct 24, 2022 at 1:13 PM Dan Williams wrote: > > Arechiga reports that his test case that failed "fast" before now ran > for 28 hours without a soft lockup report with the proposed patches > applied. So, I would consider those: > > Tested-by: Jesus Arechiga Lopez Ok, great. I really like that patch myself (and obviously liked it back when it was originally proposed), but I think it was always held back by the fact that we didn't really have any hard data for it. It does sound like we now very much have hard data for "the page waitlist complexity is now a bigger problem than the historical problem it tried to solve". So I'll happily apply it. The only question is whether it's a "let's do this for 6.2", or if it's something that we'd want to back-port anyway, and might as well apply sooner rather than later as a fix. I think that in turn then depends on just how artificial the test case was. If the test case was triggered by somebody seeing problems in real life loads, that would make the urgency a lot higher. But if it was purely a synthetic test case with no accompanying "this is what made us look at this" problem, it might be a 6.2 thing. Arechiga? Also, considering that Willy authored the patch (even if it's really just a "remove this whole code logic"), maybe he has opinions? Willy? Linus