netdev - Re: [PATCH net-next-2.6] ip: Report qdisc packet drops

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Message-ID: <4A9FCEC5.80409@gmail.com>
Date:	Thu, 03 Sep 2009 16:12:21 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	David Miller <davem@...emloft.net>, sri@...ibm.com,
	dlstevens@...ibm.com, netdev@...r.kernel.org,
	niv@...ux.vnet.ibm.com, mtk.manpages@...il.com
Subject: Re: [PATCH net-next-2.6] ip: Report qdisc packet drops

Christoph Lameter a écrit :
> On Thu, 3 Sep 2009, Eric Dumazet wrote:
>> index 29ebb0d..ebaaa7f 100644
>> --- a/net/ipv4/udp.c
>> +++ b/net/ipv4/udp.c
>> @@ -561,12 +561,18 @@ static int udp_push_pending_frames(struct sock *sk)
>>
>>  send:
>>  	err = ip_push_pending_frames(sk);
>> +	if (err) {
>> +		if (err == -ENOBUFS && !inet->recverr) {
>> +			UDP_INC_STATS_USER(sock_net(sk),
>> +					   UDP_MIB_SNDBUFERRORS, is_udplite);
> 
> This means that we now do not increment SNDBUFERRORS if IP_RECVERR is set.
> 
> I think it would be better to move UDP_INC_STATS_USER before the if
> statement. That will also simplify the code further.
> 
> 

I believe you already said this once Christoph on a previous patch, and I 
replied that in case of IP_RECVERR set, udp_push_pending_frames()
returns -ENOBUFS to its caller : udp_sendmsg()

And the caller takes care of :

out:
        ip_rt_put(rt);
        if (free)
                kfree(ipc.opt);
        if (!err)
                return len;
        /*
         * ENOBUFS = no kernel mem, SOCK_NOSPACE = no sndbuf space.  Reporting
         * ENOBUFS might not be good (it's not tunable per se), but otherwise
         * we don't have a good statistic (IpOutDiscards but it can be too many
         * things).  We could add another new stat but at least for now that
         * seems like overkill.
         */
        if (err == -ENOBUFS || test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
                UDP_INC_STATS_USER(sock_net(sk),
                                UDP_MIB_SNDBUFERRORS, is_udplite);
        }
        return err;


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