[ovs-dev] [PATCH V3 08/24] datapath: optimize flow-mask looking up

[Yi-Hung Wei]

On Wed, Sep 16, 2020 at 10:34 AM Greg Rose <gvrose8192 at gmail.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue at gmail.com>
>
> Upstream commit:
>     commit 57f7d7b9164426c496300d254fd5167fbbf205ea
>     Author: Tonghao Zhang <xiangxia.m.yue at gmail.com>
>     Date:   Fri Nov 1 22:23:49 2019 +0800
>
>     net: openvswitch: optimize flow-mask looking up
>
>     The full looking up on flow table traverses all mask array.
>     If mask-array is too large, the number of invalid flow-mask
>     increase, performance will be drop.
>
>     One bad case, for example: M means flow-mask is valid and NULL
>     of flow-mask means deleted.
>
>     +-------------------------------------------+
>     | M | NULL | ...                  | NULL | M|
>     +-------------------------------------------+
>
>     In that case, without this patch, openvswitch will traverses all
>     mask array, because there will be one flow-mask in the tail. This
>     patch changes the way of flow-mask inserting and deleting, and the
>     mask array will be keep as below: there is not a NULL hole. In the
>     fast path, we can "break" "for" (not "continue") in flow_lookup
>     when we get a NULL flow-mask.
>
>              "break"
>                 v
>     +-------------------------------------------+
>     | M | M |  NULL |...           | NULL | NULL|
>     +-------------------------------------------+
>
>     This patch don't optimize slow or control path, still using ma->max
>     to traverse. Slow path:
>     * tbl_mask_array_realloc
>     * ovs_flow_tbl_lookup_exact
>     * flow_mask_find
>
>     Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com>
>     Tested-by: Greg Rose <gvrose8192 at gmail.com>
>     Acked-by: Pravin B Shelar <pshelar at ovn.org>
>     Signed-off-by: David S. Miller <davem at davemloft.net>
>
> Cc: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> Reviewed-by: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> Signed-off-by: Greg Rose <gvrose8192 at gmail.com>
> ---

LGTM.
Acked-by: Yi-Hung Wei <yihung.wei at gmail.com>