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David Alan Gilbert" , peterx@redhat.com, Alexey Perevalov , Juraj Marcin , Markus Armbruster Subject: Re: [PATCH 08/13] migration/postcopy: Report fault latencies in blocktime In-Reply-To: <20250527231248.1279174-9-peterx@redhat.com> References: <20250527231248.1279174-1-peterx@redhat.com> <20250527231248.1279174-9-peterx@redhat.com> Date: Tue, 03 Jun 2025 13:07:07 -0300 Message-ID: <875xhc4xn8.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[7]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email, suse.de:mid, imap1.dmz-prg2.suse.org:helo] Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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 Peter Xu writes: > Blocktime so far only cares about the time one vcpu (or the whole system) > got blocked. It would be also be helpful if it can also report the latency > of page requests, which could be very sensitive during postcopy. > > Blocktime itself is sometimes not very important, especially when one > thinks about KVM async PF support, which means vCPUs are literally almost > not blocked at all because the guest OS is smart enough to switch to > another task when a remote fault is needed. > > However, latency is still sensitive and important because even if the guest > vCPU is running on threads that do not need a remote fault, the workload > that accesses some missing page is still affected. > > Add two entries to the report, showing how long it takes to resolve a > remote fault. Mention in the QAPI doc that this is not the real average > fault latency, but only the ones that was requested for a remote fault. > > Unwrap get_vcpu_blocktime_list() so we don't need to walk the list twice, > meanwhile add the entry checks in qtests for all postcopy tests. > > Cc: Markus Armbruster > Cc: Dr. David Alan Gilbert > Signed-off-by: Peter Xu Reviewed-by: Fabiano Rosas