netdev - Re: stmmac ethernet in kernel 4.4: coalescing related pauses?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1480347103.18162.58.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 28 Nov 2016 07:31:43 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     lsanfil@...vell.com, pavel@....cz, peppe.cavallaro@...com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: stmmac ethernet in kernel 4.4: coalescing related pauses?

On Mon, 2016-11-28 at 09:54 -0500, David Miller wrote:
> From: Lino Sanfilippo <lsanfil@...vell.com>
> Date: Mon, 28 Nov 2016 14:07:51 +0100
> 
> > Calling skb_orphan() in the xmit handler made this issue disappear.
> 
> This is not the way to handle this problem.
> 
> The solution is to free the SKBs in a timely manner after the
> chip has transmitted the frame.

Note that the 'pauses' described by Pavel are also caused by a too small
SO_SNDBUF value on the UDP socket.

An immediate fix, with no kernel change is to increase it.

echo 1000000 >/proc/sys/net/core/wmem_default

or

val = 1000000;
setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &val, sizeof(val));