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]) by smtp.lore.kernel.org (Postfix) with ESMTP id EFD51C369B2 for ; Mon, 14 Apr 2025 20:09:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AB30428008B; Mon, 14 Apr 2025 16:09:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A8899280088; Mon, 14 Apr 2025 16:09:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9784D28008B; Mon, 14 Apr 2025 16:09:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 797B1280088 for ; Mon, 14 Apr 2025 16:09:20 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id E080116068E for ; Mon, 14 Apr 2025 20:09:20 +0000 (UTC) X-FDA: 83333738880.20.F25E21C Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf14.hostedemail.com (Postfix) with ESMTP id A03AA100005 for ; Mon, 14 Apr 2025 20:09:18 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=R6wnx3m1; spf=none (imf14.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1744661359; 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=7iA3Ihr5qa4nH3OBiWe8HCN2AJNFi9fEeh9aTTqrmO0=; b=ryCntLgrE+Q3FV41RT6hPEUIEqn4Zc4ImAUaTRppCV/2UhpFlRDmHutJ70DzLRkTRNN/yY nDZYLOh6DKwkGbqsl3hIkImZ1+B3XGfqQ2Il7ZXWI9DehAQrN43G9iVBdNdqYsyDOsgQ2H kG1qA1mo+TTssVrPbmezyrVZqehG1mI= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=R6wnx3m1; spf=none (imf14.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744661359; a=rsa-sha256; cv=none; b=4HeDzCefFai1PXpnzn10S2gFg7LRyMd1d8o0+LZTXMKOgPDns8YtudaZhGi07NeX2N1hcy 69jQQMQ1kgtGjYdFIfKrkDr+qDIDWnqmqktitPHfN9LP/3Ab8T56NjjOEUh43xeuwRJQon YcMF0Mt6ph1IhVIhzGLZlohsNDNtUv0= 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=7iA3Ihr5qa4nH3OBiWe8HCN2AJNFi9fEeh9aTTqrmO0=; b=R6wnx3m1cKY1lEs7Z/up3F5cpj TkutvShKoVcQouAZhI2jGz+tBMOaTExFpG86lowTau6EqCZfu9xBSG3wJJS11yroH8o3ZxftptT/0 kWaV+4j/yDG2jX5En24/REJ0K33gWjNlXqMVS8qY7k4N/LXqDP4bo/L1gdKhag9gbDup6qkVsga0Y andu5Ee+CZtVXlQ/NUhPsRwOs8WLnrQWtycHX1wiysL0X9u70ZcudTdUwaAdDECqWaavZIYDu3M8G n2Dk1u2wcAcvTXZDOHjgqpcvE6tennuPyfdQ92pYXmNSTxkQC1JinWxnCZvrUJx92JOppjWeCoQIk 9f4OOyig==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1u4Q7E-0000000GtNJ-3KVt; Mon, 14 Apr 2025 20:09:12 +0000 Date: Mon, 14 Apr 2025 21:09:12 +0100 From: Matthew Wilcox To: Ankur Arora Cc: Ingo Molnar , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, luto@kernel.org, peterz@infradead.org, paulmck@kernel.org, rostedt@goodmis.org, tglx@linutronix.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: Re: [PATCH v3 1/4] x86/clear_page: extend clear_page*() for multi-page clearing Message-ID: References: <20250414034607.762653-1-ankur.a.arora@oracle.com> <20250414034607.762653-2-ankur.a.arora@oracle.com> <87wmbm1px6.fsf@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87wmbm1px6.fsf@oracle.com> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A03AA100005 X-Stat-Signature: wne8x7pmub78ikrk1c8cia5cnezwgk53 X-HE-Tag: 1744661358-852850 X-HE-Meta: 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 dTNH6QKc Ks0+KE47ihy9vDSoRRJ5vTye6KtssTz/lVAdZSqZR8q3Lq19kxfV/luRFQ0j+Q9ZJdqr0kykJw4+1bo25kGAw/RMZFZVi8dRsmaa/SSnnPJ0zZssM8PjYwe4te4RtfLb3VMDZ2yRpRcfvI+9w5DV8Ax4afJvKgPGxA65NxjvyH9cwhddKuH4PaYQXQbSm5Yimc4AOJ7FZSTpZllEzX7geJN+n/yX+BjUmxMjYsyu64rxEMJ9ojJRTvO57yqhokzY9cNXoLn75S1ysN6eLItI4N1i/PCRqiNQADrTYmq16Fqxx3xs= 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: List-Subscribe: List-Unsubscribe: On Mon, Apr 14, 2025 at 12:52:37PM -0700, Ankur Arora wrote: > Ingo Molnar writes: > >> +void clear_pages_orig(void *page, unsigned int length); > >> +void clear_pages_rep(void *page, unsigned int length); > >> +void clear_pages_erms(void *page, unsigned int length); > > > > What unit is 'length' in? If it's bytes, why is this interface > > artificially limiting itself to ~4GB? On x86-64 there's very little (if > > I was in two minds about the unit. Given that the largest page size is > 1GB, decided to go with 32bit. But, as you say below, there's no reason > to limit the x86-64 interface for MM reasons. Will fix. Actually, I think there is (and we went through this with SPARC, if you remember?) We _shouldn't_ be calling memset() with a large size (ie larger than 4GB). If we have that much memory to clear, we should be doing something smarter, like using padata to get lots of CPUs clearing individual portions of the page. I don't know how relevant this is now that you're going to be using ALTERNATIVES.