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[70.30.145.63]) by smtp.gmail.com with ESMTPSA id r3-20020ae9d603000000b007423a4ae27esm482310qkk.12.2023.03.02.13.50.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Mar 2023 13:50:52 -0800 (PST) Date: Thu, 2 Mar 2023 16:50:51 -0500 From: Peter Xu To: David Hildenbrand Cc: qemu-devel@nongnu.org, Maxim Levitsky , Stefan Hajnoczi , Juan Quintela , Paolo Bonzini , "Dr . David Alan Gilbert" , Chuang Xu , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH RFC 0/4] memory: Fix (/ Discuss) a few rcu issues Message-ID: References: <20230225163141.1209368-1-peterx@redhat.com> <6c75e2e2-5ba9-bc52-2c6c-a0bfb5f5b56f@redhat.com> <4f130497-1200-8c42-7d48-cadf54f3f6a4@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4f130497-1200-8c42-7d48-cadf54f3f6a4@redhat.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Mar 02, 2023 at 04:11:56PM +0100, David Hildenbrand wrote: > I guess the main concern here would be overhead from gabbing/releasing the > BQL very often, and blocking the BQL while we're eventually in the kernel, > clearing bitmaps, correct? More or less yes. I think it's pretty clear we move on with RCU unless extremely necessary (which I don't think..), then it's about how to fix the bug so rcu safety guaranteed. -- Peter Xu