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Szmigiero" Subject: Re: [RFC PATCH v2 8/9] migration/multifd: Don't send ram data during SYNC In-Reply-To: References: <20240722175914.24022-1-farosas@suse.de> <20240722175914.24022-9-farosas@suse.de> Date: Mon, 22 Jul 2024 18:24:16 -0300 Message-ID: <877cddyvb3.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-1.10 / 50.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; MISSING_XM_UA(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_THREE(0.00)[3]; RCVD_TLS_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email] Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:1; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: > On Mon, Jul 22, 2024 at 02:59:13PM -0300, Fabiano Rosas wrote: >> Skip saving and loading any ram data in the packet in the case of a >> SYNC. This fixes a shortcoming of the current code which requires a >> reset of the MultiFDPages_t fields right after the previous >> pending_job finishes, otherwise the very next job might be a SYNC and >> multifd_send_fill_packet() will put the stale values in the packet. >> >> By not calling multifd_ram_fill_packet(), we can stop resetting >> MultiFDPages_t in the multifd core and leave that to the client code. >> >> Actually moving the reset function is not yet done because >> pages->num==0 is used by the client code to determine whether the >> MultiFDPages_t needs to be flushed. The subsequent patches will >> replace that with a generic flag that is not dependent on >> MultiFDPages_t. >> >> Signed-off-by: Fabiano Rosas >> --- >> migration/multifd.c | 12 ++++++++++-- >> 1 file changed, 10 insertions(+), 2 deletions(-) >> >> diff --git a/migration/multifd.c b/migration/multifd.c >> index d25b8658b2..4394ca6ade 100644 >> --- a/migration/multifd.c >> +++ b/migration/multifd.c >> @@ -438,6 +438,7 @@ void multifd_send_fill_packet(MultiFDSendParams *p) >> { >> MultiFDPacket_t *packet = p->packet; >> uint64_t packet_num; >> + bool sync_packet = p->flags & MULTIFD_FLAG_SYNC; >> >> memset(packet, 0, p->packet_len); >> >> @@ -452,7 +453,9 @@ void multifd_send_fill_packet(MultiFDSendParams *p) >> >> p->packets_sent++; >> >> - multifd_ram_fill_packet(p); >> + if (!sync_packet) { >> + multifd_ram_fill_packet(p); >> + } >> >> trace_multifd_send(p->id, packet_num, >> be32_to_cpu(packet->normal_pages), >> @@ -563,7 +566,12 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp) >> p->packet_num = be64_to_cpu(packet->packet_num); >> p->packets_recved++; >> >> - ret = multifd_ram_unfill_packet(p, errp); >> + if (p->flags & MULTIFD_FLAG_SYNC) { >> + p->normal_num = 0; >> + p->zero_num = 0; > > Instead of this, I wonder whether we shouldn't touch those fields at all, > but: > > diff --git a/migration/multifd.c b/migration/multifd.c > index 0a85951d58..55abd9a1ef 100644 > --- a/migration/multifd.c > +++ b/migration/multifd.c > @@ -1547,7 +1547,9 @@ static void *multifd_recv_thread(void *opaque) > flags = p->flags; > /* recv methods don't know how to handle the SYNC flag */ > p->flags &= ~MULTIFD_FLAG_SYNC; > - has_data = p->normal_num || p->zero_num; > + > + if (!(flags & MULTIFD_FLAG_SYNC)) > + has_data = p->normal_num || p->zero_num; > qemu_mutex_unlock(&p->mutex); > } else { > /* Good idea. > >> + } else { >> + ret = multifd_ram_unfill_packet(p, errp); >> + } >> >> trace_multifd_recv(p->id, p->packet_num, p->normal_num, p->zero_num, >> p->flags, p->next_packet_size); >> -- >> 2.35.3 >>