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Date: Tue, 3 Jul 2007 15:31:31 -0500 From: olof@...om.net (Olof Johansson) To: Jeff Garzik <jgarzik@...ox.com> Cc: netdev@...r.kernel.org Subject: Re: [PATCH 2/9] pasemi_mac: Clean TX ring in poll On Mon, Jul 02, 2007 at 08:34:22AM -0400, Jeff Garzik wrote: > >Index: netdev-2.6/drivers/net/pasemi_mac.c > >=================================================================== > >--- netdev-2.6.orig/drivers/net/pasemi_mac.c > >+++ netdev-2.6/drivers/net/pasemi_mac.c > >@@ -1052,6 +1052,7 @@ static int pasemi_mac_poll(struct net_de > > int pkts, limit = min(*budget, dev->quota); > > struct pasemi_mac *mac = netdev_priv(dev); > > > >+ pasemi_mac_clean_tx(mac); > > pkts = pasemi_mac_clean_rx(mac, limit); > > Why is this needed? Is your TX interrupt mitigated or delayed somehow? On some level hardware, we only have the possibility of taking the TX interrupt after a certain number of packets, and no way of doing a (hw) timer-based one (i.e. after no packets have been sent for x ms, interrupt). Taking an interrupt for every TX packet isn't an interesting proposal, and doing it solely based on count > 1 can leave stale packets there for a long time when the network is otherwise idle. So, I would need to do a software based timer. The poll function seemed like a good enough solution for now though, since it's called periodically even when the NAPI mode is such that interrupts are enabled. > In general, drivers should only clean TX in one place. Doing so in > multiple places tends to indicate a bug somewhere. Yes, I wish I could just do it in the interrupt handler. I could do it with a dedicated timer if you prefer, but I'd still need to have two ways of entering the tx clean function. -Olof - 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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