netdev - Re: [PATCH net-next v6 05/10] net: openvswitch: optimize flow-mask looking up

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Message-ID: <CAOrHB_CkZJ+w3LvUyzUZRgnFa1JnkkKY85XsjEMvXD4geAzW4g@mail.gmail.com>
Date:   Sat, 2 Nov 2019 23:47:32 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Tonghao Zhang <xiangxia.m.yue@...il.com>
Cc:     Greg Rose <gvrose8192@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        ovs dev <dev@...nvswitch.org>
Subject: Re: [PATCH net-next v6 05/10] net: openvswitch: optimize flow-mask
 looking up

On Fri, Nov 1, 2019 at 7:24 AM <xiangxia.m.yue@...il.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@...il.com>
>
> 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@...il.com>
> Tested-by: Greg Rose <gvrose8192@...il.com>
> ---
Acked-by: Pravin B Shelar <pshelar@....org>