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Date: Sat, 30 Aug 2014 12:23:52 +0200 From: Jesper Dangaard Brouer <brouer@...hat.com> To: David Miller <davem@...emloft.net> Cc: hannes@...essinduktion.org, netdev@...r.kernel.org, therbert@...gle.com, jhs@...atatu.com, edumazet@...gle.com, jeffrey.t.kirsher@...el.com, rusty@...tcorp.com.au, dborkman@...hat.com, john.r.fastabend@...el.com, brouer@...hat.com Subject: Re: [PATCH 0/2] Get rid of ndo_xmit_flush On Fri, 29 Aug 2014 20:22:10 -0700 (PDT) David Miller <davem@...emloft.net> wrote: > From: Hannes Frederic Sowa <hannes@...essinduktion.org> > Date: Thu, 28 Aug 2014 03:42:54 +0200 > > > I wonder if we still might need a separate call for tx_flush, e.g. for > > af_packet if one wants to allow user space control of batching, MSG_MORE > > with tx hangcheck (also in case user space has control over it) or > > implement TCP_CORK alike option in af_packet. > > I disagree with allowing the user to hold a device TX queue hostage > across system calls, therefore the user should provide the entire > batch in such a case. I believe we should only do tailptr batching/delaying, when a batch of packets is readily available. I don't like the concept of speculative delaying the tailptr update, in hope a new packet will arrive shortly. We still might need a call for tx_flush, if some error case occurs while we are looping over our batch of packets. Most of these TX error situation should be hopefully be detected in the driver, and cause the driver to write the tailptr before returning. Like in commit 2367a17390 ("ixgbe: flush when in xmit_more mode and under descriptor pressure"). -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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