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Wed, 05 Apr 2023 05:45:09 -0700 (PDT) X-Google-Smtp-Source: AKy350YM3193lIgKl2aWj9mqpkVtYuh0l9dX5dcxwgxaNjVBgfvhxy0L8/57jtC9NbW/iCG3sMx10Q== X-Received: by 2002:a05:622a:1716:b0:3e4:eb03:687d with SMTP id h22-20020a05622a171600b003e4eb03687dmr4303502qtk.44.1680698709447; Wed, 05 Apr 2023 05:45:09 -0700 (PDT) Received: from vschneid.remote.csb ([154.57.232.159]) by smtp.gmail.com with ESMTPSA id t186-20020a37aac3000000b00746b7372d62sm4415939qke.27.2023.04.05.05.45.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Apr 2023 05:45:08 -0700 (PDT) From: Valentin Schneider To: Frederic Weisbecker , Peter Zijlstra Cc: 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, mtosatti@redhat.com, dhildenb@redhat.com, alougovs@redhat.com Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode In-Reply-To: References: <20230404134224.137038-1-ypodemsk@redhat.com> <20230404134224.137038-4-ypodemsk@redhat.com> <20230405114148.GA351571@hirez.programming.kicks-ass.net> Date: Wed, 05 Apr 2023 13:45:02 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2CEAD80019 X-Stat-Signature: f9jshe49mfuwcypsi1qxg7unr8bazy5r X-HE-Tag: 1680698711-80851 X-HE-Meta: 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 3S2fPFTk 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 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 05/04/23 14:05, Frederic Weisbecker wrote: > static void smp_call_function_many_cond(const struct cpumask *mask, > smp_call_func_t func, void *info, > @@ -946,10 +948,13 @@ static void smp_call_function_many_cond(const struct cpumask *mask, > #endif > cfd_seq_store(pcpu->seq_queue, this_cpu, cpu, CFD_SEQ_QUEUE); > if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { > - __cpumask_set_cpu(cpu, cfd->cpumask_ipi); > - nr_cpus++; > - last_cpu = cpu; > - > + if (!(scf_flags & SCF_NO_USER) || > + !IS_ENABLED(CONFIG_GENERIC_ENTRY) || > + ct_state_cpu(cpu) != CONTEXT_USER) { > + __cpumask_set_cpu(cpu, cfd->cpumask_ipi); > + nr_cpus++; > + last_cpu = cpu; > + } I've been hacking on something like this (CSD deferral for NOHZ-full), and unfortunately this uses the CPU-local cfd_data storage thing, which means any further smp_call_function() from the same CPU to the same destination will spin on csd_lock_wait(), waiting for the target CPU to come out of userspace and flush the queue - and we've just spent extra effort into *not* disturbing it, so that'll take a while :( I don't have much that is in a shareable state yet (though I'm supposed to talk some more about it at OSPM in <2 weeks, so I'll have to get there), but ATM I'm playing with o a bitmask (like in [1]) for coalescable stuff such as do_sync_core() for x86 instruction patching o a CSD-like queue for things that need to pass data around, using statically-allocated storage (so with a limit on how much it can be used) - the alternative being allocating a struct on sending, since you don't have a bound on how much crap you can queue on an undisturbed NOHZ-full CPU... [1]: https://lore.kernel.org/all/20210929152429.067060646@infradead.org/