linux-kernel - Re: [PATCH] net-sysfs: Slightly optimize 'xps_queue

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Message-ID: <27107a39-3073-4995-194d-5caa330d1313@wanadoo.fr>
Date:   Mon, 22 Nov 2021 20:10:51 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Xin Long <lucien.xin@...il.com>
Cc:     davem <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
        atenart@...nel.org, Alexander Duyck <alexanderduyck@...com>,
        Paolo Abeni <pabeni@...hat.com>, Wei Wang <weiwan@...gle.com>,
        network dev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] net-sysfs: Slightly optimize 'xps_queue_show()'

Le 22/11/2021 à 16:23, Xin Long a écrit :
> On Sun, Nov 21, 2021 at 2:38 PM Christophe JAILLET
> <christophe.jaillet@...adoo.fr> wrote:
>>
>> The 'mask' bitmap is local to this function. So the non-atomic
>> '__set_bit()' can be used to save a few cycles.
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> ---
>>   net/core/net-sysfs.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>> index 9c01c642cf9e..3be3f4a6add3 100644
>> --- a/net/core/net-sysfs.c
>> +++ b/net/core/net-sysfs.c
>> @@ -1452,7 +1452,7 @@ static ssize_t xps_queue_show(struct net_device *dev, unsigned int index,
>>
>>                  for (i = map->len; i--;) {
>>                          if (map->queues[i] == index) {
>> -                               set_bit(j, mask);
>> +                               __set_bit(j, mask);
>>                                  break;
>>                          }
>>                  }
>> --
>> 2.30.2
>>
> The similar optimization can seem to be done in br_vlan.c and br_if.c as well.
> 

Hi,

br_if.c should be fixed in cc0be1ad686f.

br_vlan.c was not spotted by my heuristic (a set of grep, while looking 
at something else). So, thanks for your feedback.

Feel free to propose a patch for it, it was not part of my todo list :)

If you prefer, I can also send a patch. Let me know.

CJ