On Mon, Jun 27, 2022 at 10:09:09PM -0300, Leonardo Bras wrote: > 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.
How common is this lack of SG support ? What NICs did you have that were affected ? > 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 > warn the user about it. > > Since it happens once each full dirty-bitmap scan, even in worst case > scenario it should not print a lot of warnings, and will allow tracking > how many dirty-bitmap iterations were not able to use zero-copy send. For long running migrations which are not converging, or converging very slowly there could be 100's of passes. > Signed-off-by: Leonardo Bras <leob...@redhat.com> > --- > migration/multifd.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/migration/multifd.c b/migration/multifd.c > index 684c014c86..9c62aec84e 100644 > --- a/migration/multifd.c > +++ b/migration/multifd.c > @@ -624,6 +624,9 @@ int multifd_send_sync_main(QEMUFile *f) > if (ret < 0) { > error_report_err(err); > return -1; > + } else if (ret == 1) { > + warn_report("The network device is not able to use " > + "zero-copy-send: copying is being used"); > } > } > } > -- > 2.36.1 > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|