[dpdk-dev] [dpdk-stable] [PATCH 1/2] net/virtio: fix performance regression due to TSO enabling
Thomas Monjalon
thomas.monjalon at 6wind.com
Wed Jan 11 15:51:22 CET 2017
2017-01-11 12:27, Yuanhan Liu:
> The fact that virtio net header is initiated to zero in PMD driver
> init stage means that these costly writes are unnecessary and could
> be avoided:
>
> if (hdr->csum_start != 0)
> hdr->csum_start = 0;
>
> And that's what the macro ASSIGN_UNLESS_EQUAL does. With this, the
> performance drop introduced by TSO enabling is recovered: it could
> be up to 20% in micro benchmarking.
This patch is adding a condition to assignments.
We need a benchmark on other architectures like ARM. Please anyone?
[...]
> +/* avoid write operation when necessary, to lessen cache issues */
> +#define ASSIGN_UNLESS_EQUAL(var, val) do { \
> + if ((var) != (val)) \
> + (var) = (val); \
> +} while (0)
More information about the dev
mailing list