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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 1qGKFT-008Ifc-M6; Mon, 03 Jul 2023 14:09:51 +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 7282730005E; Mon, 3 Jul 2023 16:09:50 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 59B5E2028FBD3; Mon, 3 Jul 2023 16:09:50 +0200 (CEST) Date: Mon, 3 Jul 2023 16:09:50 +0200 From: Peter Zijlstra To: Marcelo Tosatti Cc: Yair Podemsky , ppandit@redhat.com, david@redhat.com, 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, hpa@zytor.com, keescook@chromium.org, paulmck@kernel.org, frederic@kernel.org, will@kernel.org, ardb@kernel.org, samitolvanen@google.com, juerg.haefliger@canonical.com, arnd@arndb.de, rmk+kernel@armlinux.org.uk, geert+renesas@glider.be, linus.walleij@linaro.org, akpm@linux-foundation.org, sebastian.reichel@collabora.com, rppt@kernel.org, aneesh.kumar@linux.ibm.com, x86@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, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/2] send tlb_remove_table_smp_sync IPI only to necessary CPUs Message-ID: <20230703140950.GL4253@hirez.programming.kicks-ass.net> References: <20230620144618.125703-1-ypodemsk@redhat.com> <20230621074337.GF2046280@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 711E8180011 X-Stat-Signature: wkupqitbuy7hgcke4c1ec759rb9rxwg6 X-HE-Tag: 1688393427-897833 X-HE-Meta: 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 H2Qguar7 1nnaxLIVc6vowdcPsNesMMR7T6DasMpqxykz7SRMtDNQRhndCj+XeXY4xw8xCRTE909iy9WrofDcTCz09E5hiw0McAdyHdPqjPjfJQktRAON7yqrbffzqUIfAJC/MuauAAfkODHQXBHSuDlPJpb17z1esxhfpwoovEox2LAFw39oV7rueLFeovN5nSzhVXbyOuH6p7OEkoIluf3og4tOk+CPYm/m9AP7ubmLLp8mMhh1ai+7RWMx5sOd0PTdLNWH0Oy3fmBv5HAv88lTpI1QGdgHTgg== 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, Jun 22, 2023 at 09:47:22AM -0300, Marcelo Tosatti wrote: > > there's patches that cure the thp abuse of this. > > The other case where the IPI can happen is: > > CPU-0 CPU-1 > > tlb_remove_table > tlb_remove_table_sync_one > IPI > local_irq_disable > gup_fast > local_irq_enable > > > So its not only the THP case. (your CPU-1 thing is wholly irrelevant) Well, I know, but this case *should* be exceedingly rare. Last time around I asked why you all were tripping this, you pointed at the THP case. The THP case should be fixed along the lines of Jann's original patches. If you can trip this at any significant rate, then we should probably look at a better allocation scheme. It means you're really low on memory.