linux-kernel - Re: [PATCH net] rds: Fix incorrect statistics counting

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Message-ID: <b620a15a-e60e-5c35-ffef-ee485d338774@oracle.com>
Date:   Wed, 6 Sep 2017 08:58:16 -0700
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     Håkon Bugge <Haakon.Bugge@...cle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        rds-devel@....oracle.com, linux-kernel@...r.kernel.org,
        knut.omang@...cle.com
Subject: Re: [PATCH net] rds: Fix incorrect statistics counting

On 9/6/2017 8:29 AM, Håkon Bugge wrote:
> In rds_send_xmit() there is logic to batch the sends. However, if
> another thread has acquired the lock, it is considered a race and we
> yield. The code incrementing the s_send_lock_queue_raced statistics
> counter did not count this event correctly.
> 
> This commit removes a small race in determining the race and
> increments the statistics counter correctly.
> 
> Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>
> Reviewed-by: Knut Omang <knut.omang@...cle.com>
> ---
>   net/rds/send.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
Those counters are not really to give that accurate so
am not very keen to add additional cycles in send paths
and add additional code. Have you seen any real issue
or this is just a observation. s_send_lock_queue_raced
counter is never used to check for smaller increments
and hence the question.

Regards,
Santosh