From 78bbe28d5f5691330239041448cccfb339eed779 Mon Sep 17 00:00:00 2001 From: Leonardo Bras Date: Mon, 11 Jul 2022 18:11:13 -0300 Subject: [PATCH 03/11] migration/multifd: Report to user when zerocopy not working MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Leonardo Brás RH-MergeRequest: 111: zero-copy-send fixes & improvements RH-Commit: [3/6] 4f9165325b3cb8ff16d8b3b7649ff780fae0e2ad (LeoBras/centos-qemu-kvm) RH-Bugzilla: 2107466 RH-Acked-by: Miroslav Rezanina RH-Acked-by: Thomas Huth RH-Acked-by: Dr. David Alan Gilbert Some errors, like the lack of Scatter-Gather support by the network interface(NETIF_F_SG) may cause sendmsg(...,MSG_ZEROCOPY) to fail on using zero-copy, which causes it to fall back to the default copying mechanism. After each full dirty-bitmap scan there should be a zero-copy flush happening, which checks for errors each of the previous calls to sendmsg(...,MSG_ZEROCOPY). If all of them failed to use zero-copy, then increment dirty_sync_missed_zero_copy migration stat to let the user know about it. Signed-off-by: Leonardo Bras Reviewed-by: Daniel P. Berrangé Acked-by: Peter Xu Message-Id: <20220711211112.18951-4-leobras@redhat.com> Signed-off-by: Dr. David Alan Gilbert (cherry picked from commit d59c40cc483729f2e67c80e58df769ad19976fe9) Signed-off-by: Leonardo Bras --- migration/multifd.c | 2 ++ migration/ram.c | 5 +++++ migration/ram.h | 2 ++ 3 files changed, 9 insertions(+) diff --git a/migration/multifd.c b/migration/multifd.c index 0b5b41c53f..96e5f0a058 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -626,6 +626,8 @@ int multifd_send_sync_main(QEMUFile *f) if (ret < 0) { error_report_err(err); return -1; + } else if (ret == 1) { + dirty_sync_missed_zero_copy(); } } } diff --git a/migration/ram.c b/migration/ram.c index ee40e4a718..c437ff1b1f 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -406,6 +406,11 @@ static void ram_transferred_add(uint64_t bytes) ram_counters.transferred += bytes; } +void dirty_sync_missed_zero_copy(void) +{ + ram_counters.dirty_sync_missed_zero_copy++; +} + /* used by the search for pages to send */ struct PageSearchStatus { /* Current block being searched */ diff --git a/migration/ram.h b/migration/ram.h index 2c6dc3675d..34adf5cb92 100644 --- a/migration/ram.h +++ b/migration/ram.h @@ -86,4 +86,6 @@ void ram_write_tracking_prepare(void); int ram_write_tracking_start(void); void ram_write_tracking_stop(void); +void dirty_sync_missed_zero_copy(void); + #endif -- 2.31.1