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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qBsVC-00HIVK-1L; Wed, 21 Jun 2023 07:43:43 +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 0B475300222; Wed, 21 Jun 2023 09:43:38 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E49482BD11718; Wed, 21 Jun 2023 09:43:37 +0200 (CEST) Date: Wed, 21 Jun 2023 09:43:37 +0200 From: Peter Zijlstra To: Yair Podemsky Cc: mtosatti@redhat.com, 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: <20230621074337.GF2046280@hirez.programming.kicks-ass.net> References: <20230620144618.125703-1-ypodemsk@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230620144618.125703-1-ypodemsk@redhat.com> X-Rspamd-Queue-Id: 3877B20007 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: uh39ufcjrtsbqhbpwywc64edkp3ize1j X-HE-Tag: 1687333451-227611 X-HE-Meta: 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 RBlgh42M d5Qd+OJ8C9rj7vtF2jqGWthQug9n3sPxNHtoM8DF6eApx00LYNgoK68ILoMneP1aOzGDqLxGXgH0hymbd1HvvF5MTSBFMS9tx1NjIx8MQhjbZjeP4OBhC4QZHP4fakaCwhnZiz2TZGCfmgju03kKeI8o48piveoe83tLaMha16nIRQ6JG2JdTq0D6+cXq5dF3N4S/70vWx7aXo+vEKsW8qChiX0QxVoZJ4lQ+PGaFo8njGvBbfh3/P25A9pImnlSaDFfx+H+Rjlc6lrgIaDROozzT7Q== 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 Tue, Jun 20, 2023 at 05:46:16PM +0300, Yair Podemsky wrote: > Currently the tlb_remove_table_smp_sync IPI is sent to all CPUs > indiscriminately, this causes unnecessary work and delays notable in > real-time use-cases and isolated cpus. > By limiting the IPI to only be sent to cpus referencing the effected > mm. > a config to differentiate architectures that support mm_cpumask from > those that don't will allow safe usage of this feature. > > changes from -v1: > - Previous version included a patch to only send the IPI to CPU's with > context_tracking in the kernel space, this was removed due to race > condition concerns. > - for archs that do not maintain mm_cpumask the mask used should be > cpu_online_mask (Peter Zijlstra). > Would it not be much better to fix the root cause? As per the last time, there's patches that cure the thp abuse of this.