From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: netif_rx packet dumping Date: Thu, 3 Mar 2005 13:54:16 -0800 Message-ID: <20050303135416.0d6e7708@dxpl.pdx.osdl.net> References: <20050303123811.4d934249@dxpl.pdx.osdl.net> <20050303125556.6850cfe5.davem@davemloft.net> <1109884688.1090.282.camel@jzny.localdomain> <20050303132143.7eef517c@dxpl.pdx.osdl.net> <1109885065.1098.285.camel@jzny.localdomain> <20050303133237.5d64578f.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: hadi@cyberus.ca, rhee@eos.ncsu.edu, jheffner@psc.edu, Yee-Ting.Li@nuim.ie, baruch@ev-en.org, netdev@oss.sgi.com To: "David S. Miller" In-Reply-To: <20050303133237.5d64578f.davem@davemloft.net> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Thu, 3 Mar 2005 13:32:37 -0800 "David S. Miller" wrote: > On 03 Mar 2005 16:24:25 -0500 > jamal wrote: > > > Ok, this does sound more reasonable. Out of curiosity, are packets being > > dropped at the socket queue? Why is "dump till empty" behaviour screwing > > over TCP. > > Because it does the same thing tail-drop in routers do. > It makes everything back off a lot and go into slow start. > If we'd just drop 1 packet per flow or something like that > (so it could be fixed with a quick fast retransmit), TCP > would avoid regressing into slow start. Maybe a simple Random Exponential Drop (RED) would be more friendly. > You say "use a NAPI driver", but netif_rx() _IS_ a NAPI driver. > process_backlog() adheres to quotas and every other stabilizing > effect NAPI drivers use, the only missing part is the RX interrupt > disabling. > > We should eliminate the max backlog thing completely. There is > no need for it. Still need some bound, because if process_backlog is running slower than the net; then the queue could grow till memory exhausted from skbuff's.