netdev - Re: [PATCH net-next v7 1/1] net:openvswitch:reduce cpu_used

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Date:   Sat, 4 Feb 2023 14:28:21 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Eddy Tao <taoyuan_eddy@...mail.com>
Cc:     netdev@...r.kernel.org, Pravin B Shelar <pshelar@....org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, dev@...nvswitch.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v7 1/1] net:openvswitch:reduce cpu_used_mask
 memory

On Fri, Feb 03, 2023 at 11:42:45PM +0800, 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>

nit: I think the correct prefix for the patch subject is 'openvswitch:'
     And there should be a space after the prefix.

[PATCH net-next v8 1/1] openvswitch: reduce cpu_used_mask