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 6C657C76196 for ; Thu, 6 Apr 2023 15:07:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 07E386B007B; Thu, 6 Apr 2023 11:07:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 054B36B007D; Thu, 6 Apr 2023 11:07:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E88066B007E; Thu, 6 Apr 2023 11:07:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id D9CF96B007B for ; Thu, 6 Apr 2023 11:07:03 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id A36EB41353 for ; Thu, 6 Apr 2023 15:07:03 +0000 (UTC) X-FDA: 80651293926.04.7E0F181 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf22.hostedemail.com (Postfix) with ESMTP id 20667C0038 for ; Thu, 6 Apr 2023 15:07:00 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=j7Fc4zxU; spf=none (imf22.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1680793621; a=rsa-sha256; cv=none; b=3MLIn1+3nKI9X3PhTI8jF9WFuCy3JRh5KvWpJeDULhNc8x7a6QpxXhiiLKbteUzWl3ixyJ PFWyT3hEEnMd1ba2X6IU74MZfOUo85271LhBwF5HQMiRNc/2XNfBPjGWXZT1VGaDh1iRXk 4gB5EUM5sejbBzodKvG4uEPrIKw1dJM= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=j7Fc4zxU; spf=none (imf22.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1680793621; 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=w0SObkY+pHUk30QF/T/49A8Ec+D+ZKrAW6VBtZQhwf4=; b=Fsz5I8aYDW68Ju7/QwO0twXw7ywYzXky+4EYqSjZs/64mGsKQBVyGPK0kYr+/NNZtbpR6B 5Kb7rOrkSdcRKaYOF/EbvvAXcGmj4O5PUAqvnpCKpFImU+FzoSvm+36kHKc6n4uyHBCk5X hsdADS//w88CP8mPnCsqPQx6RLGy5mI= 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=w0SObkY+pHUk30QF/T/49A8Ec+D+ZKrAW6VBtZQhwf4=; b=j7Fc4zxUxTtlcw5lRvD3o/FO95 vd+g08D1sixa2R2KaSiy1LVmxgPohYklc4gHHSm1Taw7s0FRExXtIAJcK83szPro54l4LbaLUVEI0 DuYemUHB6v+udPGcT3CyayjiJP6rcBcfxYdSnyZl3r4HZeRhKOYjCPH03Nr4Zh/3MKjTT4PLydE08 gNp/OmtpGKGtGtscTMcA5G2I+asU9E2lhirwZkJNyrP8+22twBUl6F6yeFeznVIX6v57KKJdlNf91 3m9t5jwv6kmKwFYiwD1TYX4EXCIIw0+dwy9Z6NHfS9Su7GySsref4CZXHV3d3rT1j5ccaqf/WLFTF YxR1HpFA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pkRC4-00HWBW-No; Thu, 06 Apr 2023 15:06:32 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 805333000DC; Thu, 6 Apr 2023 17:06:31 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 661CC212E36AE; Thu, 6 Apr 2023 17:06:31 +0200 (CEST) Date: Thu, 6 Apr 2023 17:06:31 +0200 From: Peter Zijlstra To: David Hildenbrand Cc: Marcelo Tosatti , Frederic Weisbecker , Yair Podemsky , linux@armlinux.org.uk, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, will@kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, arnd@arndb.de, keescook@chromium.org, paulmck@kernel.org, jpoimboe@kernel.org, samitolvanen@google.com, ardb@kernel.org, juerg.haefliger@canonical.com, rmk+kernel@armlinux.org.uk, geert+renesas@glider.be, tony@atomide.com, linus.walleij@linaro.org, sebastian.reichel@collabora.com, nick.hawkins@hpe.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, vschneid@redhat.com, dhildenb@redhat.com, alougovs@redhat.com, jannh@google.com Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode Message-ID: <20230406150631.GR386572@hirez.programming.kicks-ass.net> References: <20230404134224.137038-1-ypodemsk@redhat.com> <20230404134224.137038-4-ypodemsk@redhat.com> <20230405195226.GB365912@hirez.programming.kicks-ass.net> <20230406132928.GM386572@hirez.programming.kicks-ass.net> <20230406140423.GA386634@hirez.programming.kicks-ass.net> <1654e2d5-5a32-a253-e335-0ee42f69f5ef@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1654e2d5-5a32-a253-e335-0ee42f69f5ef@redhat.com> X-Rspam-User: X-Rspamd-Queue-Id: 20667C0038 X-Rspamd-Server: rspam01 X-Stat-Signature: iqodb11jjq7369unz5h3c7ydq14hpcoo X-HE-Tag: 1680793620-127844 X-HE-Meta: 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 oXiZSoUS H4xsr0zuEuGi3SatpumHPO/c9aK+h60blKVCbl+/EAJ7pTHYP4jK33VQlMCRcufxcfrIpXgSIcbWlgNEQudeN88uGkXR2ab41Vwu36pNIi8l8hHe1oX2m8LFH7OZvegYbPpMIzDPXnf6YmHELvgl2jGP9+Y2nGfvDtdfKzZRXPtrUnTWUfWZgVSXl30Ps5lgRuoErFOhQEBxEeiSYPb7kofSlD5CS9bd5HyhX8D5OxegGOPGLTbOecCr/XjoYCwTj4ZssfNLE36vi7D19HPtD+3hFZRfMohaXkNK0 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 Thu, Apr 06, 2023 at 04:42:02PM +0200, David Hildenbrand wrote: > On 06.04.23 16:04, Peter Zijlstra wrote: > > On Thu, Apr 06, 2023 at 03:29:28PM +0200, Peter Zijlstra wrote: > > > On Thu, Apr 06, 2023 at 09:38:50AM -0300, Marcelo Tosatti wrote: > > > > > > > > To actually hit this path you're doing something really dodgy. > > > > > > > > Apparently khugepaged is using the same infrastructure: > > > > > > > > $ grep tlb_remove_table khugepaged.c > > > > tlb_remove_table_sync_one(); > > > > tlb_remove_table_sync_one(); > > > > > > > > So just enabling khugepaged will hit that path. > > > > > > Urgh, WTF.. > > > > > > Let me go read that stuff :/ > > > > At the very least the one on collapse_and_free_pmd() could easily become > > a call_rcu() based free. > > > > I'm not sure I'm following what collapse_huge_page() does just yet. > > It wants to replace a leaf page table by a THP (Transparent Huge Page mapped > by a PMD). So we want to rip out a leaf page table while other code > (GUP-fast) might still be walking it. Right, I got that far. > In contrast to freeing the page table, > we put it into a list where it can be reuse when having to PTE-map a THP > again. Yeah, this is the bit I couldn't find, that code is a bit of a maze. > Now, similar to after freeing the page table, someone else could reuse that > page table and modify it. So ideally we'll RCU free the page instead of sticking it on that list.