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[174.95.215.133]) by smtp.gmail.com with ESMTPSA id z89sm6017ilk.4.2020.10.19.15.57.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Oct 2020 15:57:28 -0700 (PDT) From: Peter Xu To: qemu-devel@nongnu.org Subject: [PATCH v5 4/6] migration: Sync requested pages after postcopy recovery Date: Mon, 19 Oct 2020 18:57:18 -0400 Message-Id: <20201019225720.172743-5-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201019225720.172743-1-peterx@redhat.com> References: <20201019225720.172743-1-peterx@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/19 15:28:27 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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_H4=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Thomas Huth , Juan Quintela , Xiaohui Li , "Dr . David Alan Gilbert" , peterx@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" We synchronize the requested pages right after a postcopy recovery happens. This helps to synchronize the prioritized pages on source so that the faulted threads can be served faster. Reported-by: Xiaohui Li Signed-off-by: Peter Xu Reviewed-by: Dr. David Alan Gilbert --- migration/savevm.c | 57 ++++++++++++++++++++++++++++++++++++++++++ migration/trace-events | 1 + 2 files changed, 58 insertions(+) diff --git a/migration/savevm.c b/migration/savevm.c index d2e141f7b1..33acbba1a4 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -2011,6 +2011,49 @@ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis) return LOADVM_QUIT; } +/* We must be with page_request_mutex held */ +static gboolean postcopy_sync_page_req(gpointer key, gpointer value, + gpointer data) +{ + MigrationIncomingState *mis = data; + void *host_addr = (void *) key; + ram_addr_t rb_offset; + RAMBlock *rb; + int ret; + + rb = qemu_ram_block_from_host(host_addr, true, &rb_offset); + if (!rb) { + /* + * This should _never_ happen. However be nice for a migrating VM to + * not crash/assert. Post an error (note: intended to not use *_once + * because we do want to see all the illegal addresses; and this can + * never be triggered by the guest so we're safe) and move on next. + */ + error_report("%s: illegal host addr %p", __func__, host_addr); + /* Try the next entry */ + return FALSE; + } + + ret = migrate_send_rp_message_req_pages(mis, rb, rb_offset); + if (ret) { + /* Please refer to above comment. */ + error_report("%s: send rp message failed for addr %p", + __func__, host_addr); + return FALSE; + } + + trace_postcopy_page_req_sync(host_addr); + + return FALSE; +} + +static void migrate_send_rp_req_pages_pending(MigrationIncomingState *mis) +{ + WITH_QEMU_LOCK_GUARD(&mis->page_request_mutex) { + g_tree_foreach(mis->page_requested, postcopy_sync_page_req, mis); + } +} + static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis) { if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) { @@ -2033,6 +2076,20 @@ static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis) /* Tell source that "we are ready" */ migrate_send_rp_resume_ack(mis, MIGRATION_RESUME_ACK_VALUE); + /* + * After a postcopy recovery, the source should have lost the postcopy + * queue, or potentially the requested pages could have been lost during + * the network down phase. Let's re-sync with the source VM by re-sending + * all the pending pages that we eagerly need, so these threads won't get + * blocked too long due to the recovery. + * + * Without this procedure, the faulted destination VM threads (waiting for + * page requests right before the postcopy is interrupted) can keep hanging + * until the pages are sent by the source during the background copying of + * pages, or another thread faulted on the same address accidentally. + */ + migrate_send_rp_req_pages_pending(mis); + return 0; } diff --git a/migration/trace-events b/migration/trace-events index e4d5eb94ca..0fbfd2da60 100644 --- a/migration/trace-events +++ b/migration/trace-events @@ -49,6 +49,7 @@ vmstate_save(const char *idstr, const char *vmsd_name) "%s, %s" vmstate_load(const char *idstr, const char *vmsd_name) "%s, %s" postcopy_pause_incoming(void) "" postcopy_pause_incoming_continued(void) "" +postcopy_page_req_sync(void *host_addr) "sync page req %p" # vmstate.c vmstate_load_field_error(const char *field, int ret) "field \"%s\" load failed, ret = %d"