From: Leonardo Bras <leob...@redhat.com> 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 <leob...@redhat.com> Reviewed-by: Daniel P. Berrangé <berra...@redhat.com> Acked-by: Peter Xu <pet...@redhat.com> Message-Id: <20220711211112.18951-4-leob...@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com> --- 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 1e49594b02..586ddc9d65 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -624,6 +624,8 @@ 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 4fbad74c6c..b94669ba5d 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -434,6 +434,11 @@ 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 5d90945a6e..c7af65ac74 100644 --- a/migration/ram.h +++ b/migration/ram.h @@ -89,4 +89,6 @@ 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 -- 2.36.1