netdev - Re: [ovs-dev] [PATCH net-next v8 1/1] net: openvswitch: reduce cpu_used

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Message-ID: <BB520D08-D1D3-45DB-A3AE-008E8DF48F81@redhat.com>
Date:   Mon, 06 Feb 2023 12:21:53 +0100
From:   Eelco Chaudron <echaudro@...hat.com>
To:     Eddy Tao <taoyuan_eddy@...mail.com>
Cc:     netdev@...r.kernel.org, dev@...nvswitch.org,
        linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [ovs-dev] [PATCH net-next v8 1/1] net: openvswitch: reduce
 cpu_used_mask memory



On 5 Feb 2023, at 2:35, Eddy Tao wrote:

> Use actual CPU number instead of hardcoded value to decide the size
> of 'cpu_used_mask' in 'struct sw_flow'. Below is the reason.
>
> 'struct cpumask cpu_used_mask' is embedded in struct sw_flow.
> Its size is hardcoded to CONFIG_NR_CPUS bits, which can be
> 8192 by default, it costs memory and slows down ovs_flow_alloc.
>
> To address this:
>  Redefine cpu_used_mask to pointer.
>  Append cpumask_size() bytes after 'stat' to hold cpumask.
>  Initialization cpu_used_mask right after stats_last_writer.
>
> APIs like cpumask_next and cpumask_set_cpu never access bits
> beyond cpu count, cpumask_size() bytes of memory is enough.
>
> Signed-off-by: Eddy Tao <taoyuan_eddy@...mail.com>

The changes look good to me. Hopefully this is the last revision ;)

Acked-by: Eelco Chaudron <echaudro@...hat.com>