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 C39C0FCC056 for ; Fri, 6 Mar 2026 18:25:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E29D86B0096; Fri, 6 Mar 2026 13:25:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DD7726B0098; Fri, 6 Mar 2026 13:25:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CB9476B0099; Fri, 6 Mar 2026 13:25:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id BCFD56B0096 for ; Fri, 6 Mar 2026 13:25:05 -0500 (EST) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 5495E16064B for ; Fri, 6 Mar 2026 18:25:05 +0000 (UTC) X-FDA: 84516464970.18.216D517 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf07.hostedemail.com (Postfix) with ESMTP id 8CBA640006 for ; Fri, 6 Mar 2026 18:25:03 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=tfK5QBJ7; spf=pass (imf07.hostedemail.com: domain of vbabka@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1772821503; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6pV7WHaJGDa1IFAIeltnCF1PS/BAuwPgVK8PONG7Ltg=; b=Vcbq3lwtVjgZd8xXkyN65+IQ75UP8IjrlqbPvfARIg1NifQc4AQTz3j/be/Xv7YLfZ9C7U VP0KJZEoqhTw3dgBMqqWmfyh7hozc5XA7m8N3o8eYecN/jA728rtfl/rLDN1MtqRBzBBLP ytcqTcEC5XR8uAl82Agvv+PqQ33QYVc= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772821503; a=rsa-sha256; cv=none; b=pyq2wWqb+NmVU+Z2LIOIH0TymCMTKNNArB6bu8hXdPDrHQhjpRxasxzsA6ezUn0TjnWCTu VqQ/Vs1vKG/AvPTvBki1MXRE2Q/rb9+pixSTbe3GMwmtSwQrQ0t9cGaykp/03h9oui1kqn AUfZ6cWXz7yAkhX3Fc/FdvA2Q7MdR/k= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=tfK5QBJ7; spf=pass (imf07.hostedemail.com: domain of vbabka@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 5902A43AD0; Fri, 6 Mar 2026 18:25:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1F1DC4CEF7; Fri, 6 Mar 2026 18:24:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772821502; bh=1uq9z4/ibsX1WTmZECq30MMk5X7c41BLu0dsdJbzLvE=; h=Date:From:Subject:To:Cc:References:In-Reply-To:From; b=tfK5QBJ7Ly5+nGF8m5oRBcOsYY4YQPlgbMZyXPT/Sy5R9XEvdzb/Yt00+6n+K1QAj arfzxw5dLDkTzgho+/gGrOaS35/5cO7ue4p0Zyer0FIgDGBfe9NMaB7xQJGmCQjWQr DdrS12z4fGzB588aXtYgq/Re3WU1aKw+ZKwzNbHvxrPslEhKbRMNaw7/jazbhEI029 00PVOU5NUzS/ZcusgWmGELcVY3bbB0I+JazrgyqybGM5lksJAhuCac9RUGe5yBjyUV C1rF6N2m8eD4waahoa0jqEKoEjSNfMzBhZYVchJEPelKuO46cEMTPqMTG1eUeZZrSV IPgDlRrvDBYLw== Message-ID: Date: Fri, 6 Mar 2026 19:24:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Vlastimil Babka Subject: Re: [PATCH 1/8] mm: use zone lock guard in reserve_highatomic_pageblock() To: Steven Rostedt , Andrew Morton Cc: Dmitry Ilvokhin , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Peter Zijlstra References: <20260306095336.a79fcc869a7f6d2b2e97501b@linux-foundation.org> <20260306130052.7da8eab3@gandalf.local.home> Content-Language: en-US In-Reply-To: <20260306130052.7da8eab3@gandalf.local.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: smjxpbnamue7hxbgnwrkm7p8jbfbkfr6 X-Rspam-User: X-Rspamd-Queue-Id: 8CBA640006 X-Rspamd-Server: rspam12 X-HE-Tag: 1772821503-792450 X-HE-Meta: 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 5fYWiHDd Gu21VINy4aiwWbbE4/Ys2RZMO6wMj9KgfsilgY+0my+E1hS2WzqcWZYAAGjvgAL+W+lQwHYJfHREV4cp+VSpbFjbfUuUa3jRIUq8C/ODPX/fiQD8/im+RgVmc3lNLONsspgYCdTIs8Z56xR3nhUtl2y2MralBARtVRZfPyvbxHxVyYcnC0gsrWlmFdApTPmGhWNglfcpdxTVPxxmeQme4ZLw+4Y1sBcQblRmC+itoIXzc0qTqlBrMSShaeBov8Lc3tNoJiSMIS0+u3GPSwAGGNPumK4c6s2ULqd6yOHtHqWFhH3xpNo+7BISw8rQAVSq6/jSwQk8j94lNM33xSUiD7Txp/Ids1xZ22JEKK4ao7kDbokc4plaxD4eYqQM/VYqM7xICn4bj0U7vXSfonDCg56wGbrXEQVwCnRUR5LAU0PiQY/zB2bWXTbejS4g7kttLDwgR3gvjYDt/taUhxqlPxee8rw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/6/26 19:00, Steven Rostedt wrote: > > [ Adding Peter ] > > On Fri, 6 Mar 2026 09:53:36 -0800 > Andrew Morton wrote: > >> On Fri, 6 Mar 2026 16:05:35 +0000 Dmitry Ilvokhin wrote: >> >> > Use the newly introduced zone_lock_irqsave lock guard in >> > reserve_highatomic_pageblock() to replace the explicit lock/unlock and >> > goto out_unlock pattern with automatic scope-based cleanup. >> > >> > ... >> > >> > - zone_lock_irqsave(zone, flags); >> > + guard(zone_lock_irqsave)(zone); >> >> guard() is cute, but this patch adds a little overhead - defconfig >> page_alloc.o text increases by 32 bytes, presumably all in >> reserve_highatomic_pageblock(). More instructions, larger cache >> footprint. I get this: Function old new delta get_page_from_freelist 6389 6452 +63 >> So we're adding a little overhead to every user's Linux machine for all >> time. In return for which the developers get a little convenience and >> maintainability. > > I think maintainability is of importance. Is there any measurable slowdown? > Or are we only worried about the text size increase? > >> >> Is it worth it? > > This is being done all over the kernel. Perhaps we should look at ways to > make the generic infrastructure more performant? Yeah I don't think the guard construct in this case should be doing anything here that wouldn't allow the compiler to compile to the exactly same result as before? Either there's some problem with the infra, or we're just victim of compiler heuristics. In both cases imho worth looking into rather than rejecting the construct. > -- Steve