From: Paolo Abeni <pabeni@xxxxxxxxxx>
Date: Tue, 24 Apr 2018 10:34:36 +0200
> Similar to commit a2ac99905f1e ("vhost-net: set packet weight of
> tx polling to 2 * vq size"), we need a packet-based limit for
> handler_rx, too - elsewhere, under rx flood with small packets,
> tx can be delayed for a very long time, even without busypolling.
>
> The pkt limit applied to handle_rx must be the same applied by
> handle_tx, or we will get unfair scheduling between rx and tx.
> Tying such limit to the queue length makes it less effective for
> large queue length values and can introduce large process
> scheduler latencies, so a constant valued is used - likewise
> the existing bytes limit.
>
> The selected limit has been validated with PVP[1] performance
> test with different queue sizes:
>
> queue size 256 512 1024
>
> baseline 366 354 362
> weight 128 715 723 670
> weight 256 740 745 733
> weight 512 600 460 583
> weight 1024 423 427 418
>
> A packet weight of 256 gives peek performances in under all the
> tested scenarios.
>
> No measurable regression in unidirectional performance tests has
> been detected.
>
> [1] https://developers.redhat.com/blog/2017/06/05/measuring-and-comparing-open-vswitch-performance/
>
> Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Applied to net-next, thanks.
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