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migration/multifd: Report to user when zerocopy not working

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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 <leobras@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220711211112.18951-4-leobras@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Leonardo Bras 2022-07-11 18:11:13 -03:00 committed by Dr. David Alan Gilbert
parent cf20c89733
commit d59c40cc48
3 changed files with 9 additions and 0 deletions
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2
migration/multifd.c
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@ -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();
}
}
}

5
migration/ram.c
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@ -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 */

2
migration/ram.h
View File

@ -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