From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lino Sanfilippo Subject: Re: stmmac ethernet in kernel 4.4: coalescing related pauses? Date: Mon, 28 Nov 2016 16:57:35 +0100 Message-ID: <920b1148-a77d-0b69-01b0-b14bcbdf8648@marvell.com> References: <20161123105125.GA26394@amd> <20161128.095431.856183735501262965.davem@davemloft.net> <1480347103.18162.58.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: , , , To: Eric Dumazet , David Miller Return-path: In-Reply-To: <1480347103.18162.58.camel@edumazet-glaptop3.roam.corp.google.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 28.11.2016 16:31, Eric Dumazet wrote: > On Mon, 2016-11-28 at 09:54 -0500, David Miller wrote: >> From: Lino Sanfilippo >> 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)); > I wonder if the best fix would be indeed to deactivate irq coalescing completely. Does it make any sense at all to use it if a driver uses NAPI already? Regards, Lino