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027b17603b
Under heavy load vhost busypoll may run without suppressing notification. For example tx zerocopy callback can push tx work while handle_tx() is running, then busyloop exits due to vhost_has_work() condition and enables notification but immediately reenters handle_tx() because the pushed work was tx. In this case handle_tx() tries to disable notification again, but when using event_idx it by design cannot. Then busyloop will run without suppressing notification. Another example is the case where handle_tx() tries to enable notification but avail idx is advanced so disables it again. This case also leads to the same situation with event_idx. The problem is that once we enter this situation busyloop does not work under heavy load for considerable amount of time, because notification is likely to happen during busyloop and handle_tx() immediately enables notification after notification happens. Specifically busyloop detects notification by vhost_has_work() and then handle_tx() calls vhost_enable_notify(). Because the detected work was the tx work, it enters handle_tx(), and enters busyloop without suppression again. This is likely to be repeated, so with event_idx we are almost not able to suppress notification in this case. To fix this, poll the work instead of enabling notification when busypoll is interrupted by something. IMHO vhost_has_work() is kind of interruption rather than a signal to completely cancel the busypoll, so let's run busypoll after the necessary work is done. Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp> Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| .. | ||
| Kconfig | ||
| Kconfig.vringh | ||
| Makefile | ||
| net.c | ||
| scsi.c | ||
| test.c | ||
| test.h | ||
| vhost.c | ||
| vhost.h | ||
| vringh.c | ||
| vsock.c | ||