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[209.85.208.175]) by smtp.gmail.com with ESMTPSA id w29sm3141068lfq.65.2020.07.27.10.02.04 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jul 2020 10:02:05 -0700 (PDT) Received: by mail-lj1-f175.google.com with SMTP id q6so18042991ljp.4 for ; Mon, 27 Jul 2020 10:02:04 -0700 (PDT) X-Received: by 2002:a2e:991:: with SMTP id 139mr10110196ljj.314.1595869323443; Mon, 27 Jul 2020 10:02:03 -0700 (PDT) MIME-Version: 1.0 References: <20200723211432.b31831a0df3bc2cbdae31b40@linux-foundation.org> <20200724041508.QlTbrHnfh%akpm@linux-foundation.org> <0323de82-cfbd-8506-fa9c-a702703dd654@linux.alibaba.com> <20200727110512.GB25400@gaia> In-Reply-To: <20200727110512.GB25400@gaia> From: Linus Torvalds Date: Mon, 27 Jul 2020 10:01:47 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [patch 01/15] mm/memory.c: avoid access flag update TLB flush for retried page fault To: Catalin Marinas Cc: Yu Xu , Andrew Morton , Johannes Weiner , Hillf Danton , Hugh Dickins , Josef Bacik , "Kirill A . Shutemov" , Linux-MM , mm-commits@vger.kernel.org, Will Deacon , Matthew Wilcox , Yang Shi Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: A72736D74 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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 Mon, Jul 27, 2020 at 4:05 AM Catalin Marinas wrote: > > It leaves the spurious flush in place but only local (though note that > in a guest under KVM, all local TLBIs are upgraded to inner-shareable, > so you'd not get the performance benefit). Is there a way to mark and override that for this case? It really makes no sense to distribute the TLB invalidation. Even if some virtualization manager switches CPU's from under us at _just_ the wrong moment, it doesn't matter. It's a spurious thing, at worst we'll take one more exception on the other CPU that didn't get flushed after all. Linus