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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3D4B5F3C24C for ; Mon, 9 Mar 2026 13:11:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A73416B0089; Mon, 9 Mar 2026 09:11:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A4B2E6B008A; Mon, 9 Mar 2026 09:11:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 977F76B008C; Mon, 9 Mar 2026 09:11:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 88C646B0089 for ; Mon, 9 Mar 2026 09:11:05 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 17C72B639D for ; Mon, 9 Mar 2026 13:11:05 +0000 (UTC) X-FDA: 84526560090.23.1041262 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf26.hostedemail.com (Postfix) with ESMTP id E34AB140016 for ; Mon, 9 Mar 2026 13:11:02 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=QXH3c3N2; spf=none (imf26.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1773061863; 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=MP91r6c+y7giftvLR1OcIBEAD8RMncykz3hjSEiLD3U=; b=35/AqWoWSYoEFXlUat1l3T1GQvOGzHoiQgUKVrBIHIBVaCqBXszKpd9blYX7oDWv/hHg41 w2Fb1RcnOrB9ktjAkhJAwu46ojKHGwMhOHFLRbKNC9NzXQN4OOLeNxlHis84S2g7DZJ3ls fvTg4lvjwt1vFL6ovyvNtWKN3YdSsDg= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=QXH3c3N2; spf=none (imf26.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773061863; a=rsa-sha256; cv=none; b=agGY49+IDozKaD1LIflBa5+c/ITNU/TF3KcAoM0ecpTL+uY0FHt+SGkXFGoILeOrI0P4mN Tbv82WZr3Ci3Pb5io/06mRxHrnY7sB1Ckirh88RPOJzyIUuOSuBT1zp/RNlfkfAhqHXg1i OLkSQViXUIu5xriaW14pgEPOir5Omq8= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=MP91r6c+y7giftvLR1OcIBEAD8RMncykz3hjSEiLD3U=; b=QXH3c3N2WvdAVaSk98rBw2QTWS hU5Khg29+699uZHVtoU0uZoe1D1JffMnyRcTC8uQ7cbi7MTdGwkhkTrFM4BxLE7mmonVLmntz5SAP IictCbrRUlk+lXjcQDDSzGiCOkzLnQqIORtItpqOvW7X3s3kgk/cOE2ElyskYVfLRf6B9ynL23R4e rK4ES1g8jxDUN5iuuqwgC19keOsLHKfFRHgg/jnWLnecoWDm4mQwnmV+S3bnIwP5npEOOGBJmsDeb bKuls447s9ARbiGV44qcLe2izeke7FZkNGhnaK8b9FBRLdXrdUrvZp0LPwM3NlLPxUgj1t/dIwV/G lBt5MxcA==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vzaNj-00000005ZGM-0n5j; Mon, 09 Mar 2026 13:10:47 +0000 Date: Mon, 9 Mar 2026 13:10:46 +0000 From: Matthew Wilcox To: Dmitry Ilvokhin Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Axel Rasmussen , Yuanchu Xie , Wei Xu , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , "Rafael J. Wysocki" , Pavel Machek , Len Brown , Brendan Jackman , Johannes Weiner , Zi Yan , Oscar Salvador , Qi Zheng , Shakeel Butt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH v4 0/5] mm: zone lock tracepoint instrumentation Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: zukj8gyrhs9fhfgsbeddr1zjanpp795n X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: E34AB140016 X-HE-Tag: 1773061862-616729 X-HE-Meta: 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 AZj6RVyF iJlYLJ+53kpP7kMQDT9TXt9hybS3N+3exB9AmRbJ29x/W5FDWkBsK996CdmcNWZf9EokTL/KaArx79Rvk5koHwWXU4ZZxpNxqKmH8nzeLuDDSZ8cWnH6597WxVyDxciKj8R74OWQvkyJ8ggmTpuYGqz7VwAXOLiklyiVQafCqe7Ca+kyfu2ByW6p+Fj5tpUpT0fYpIDLqA1+BDddb7YwVAUq9K9nWUZ4gk2NJkKnKvzLl6jfqkJVyWD2h8YY05H/6zdda Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 27, 2026 at 04:00:22PM +0000, Dmitry Ilvokhin wrote: > Zone lock contention can significantly impact allocation and > reclaim latency, as it is a central synchronization point in > the page allocator and reclaim paths. Improved visibility into > its behavior is therefore important for diagnosing performance > issues in memory-intensive workloads. > > On some production workloads at Meta, we have observed noticeable > zone lock contention. Deeper analysis of lock holders and waiters > is currently difficult with existing instrumentation. > > While generic lock contention_begin/contention_end tracepoints > cover the slow path, they do not provide sufficient visibility > into lock hold times. In particular, the lack of a release-side > event makes it difficult to identify long lock holders and > correlate them with waiters. As a result, distinguishing between > short bursts of contention and pathological long hold times > requires additional instrumentation. > > This patch series adds dedicated tracepoint instrumentation to > zone lock, following the existing mmap_lock tracing model. I don't like this at all. We have CONFIG_LOCK_STAT. That should be improved insted of coming up with one-offs for every single lock that someone deems "special".