From: Arnd Bergmann <arnd@arndb•de>
To: Stephen Hemminger <shemminger@osdl•org>
Cc: akpm@osdl•org, netdev@vger•kernel.org,
James K Lewis <jklewis@us•ibm.com>,
linux-kernel@vger•kernel.org, linuxppc-dev@ozlabs•org,
Jens Osterkamp <Jens.Osterkamp@de•ibm.com>,
Jeff Garzik <jgarzik@pobox•com>,
David Miller <davem@davemloft•net>
Subject: Re: [RFC] HOWTO use NAPI to reduce TX interrupts
Date: Sat, 19 Aug 2006 13:25:18 +0200 [thread overview]
Message-ID: <200608191325.19557.arnd@arndb.de> (raw)
In-Reply-To: <44E7BB7F.7030204@osdl.org>
On Sunday 20 August 2006 03:31, Stephen Hemminger wrote:
>=20
> The reason reclaim via poll() is efficient is because it avoid causing a=
=20
> softirq that is
> necessary when skb_free_irq() is done. Instead it reuses the softirq=20
> from the poll() routine.=20
Ok, I completely missed this point so far, thanks for the info.
> Like all Rx NAPI, using poll() for reclaim means:=20
> =A0 =A0 + aggregating multiple frames in one irq
> =A0 =A0 - increased overhead of twiddling with the IRQ mask
> =A0 =A0 - more ways to get driver stuck
What is the best way to treat the IRQ mask for TX interrupts?
I guess it should be roughly:
=2D off when we expect ->poll() to be called, i.e. after calling
netif_rx_schedule() or returning after a partial rx from poll().
=2D off when there are no packets left in the TX queue
=2D on while RX interrupts are on and we're waiting for packets
to be transmitted.
> Some drivers do all their irq work in the poll() routine (including PHY=20
> handling).
> This is good if reading the IRQ status does an auto mask operation.
>=20
> The whole NAPI documentation area is a mess and needs a good writer
> to do some major restructuring. It should also be split into reference=20
> information,
> tutorial and guide sections.
I won't be able to do that work, I'm neither a good writer nor a networking
person.
Do you think we should still merge a section like the text I wrote up, even
if it makes the text even less well structured? Should I maybe add it
somewhere else than the appendix?
Arnd <><
next prev parent reply other threads:[~2006-08-19 11:26 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-18 22:07 [PATCH 0/6]: powerpc/cell spidernet ethernet driver update Linas Vepstas
2006-08-18 22:20 ` [PATCH 1/6]: powerpc/cell spidernet burst alignment patch Linas Vepstas
2006-08-18 22:51 ` Arnd Bergmann
2006-08-18 22:21 ` [PATCH 2/6]: powerpc/cell spidernet low watermark patch Linas Vepstas
2006-08-18 23:09 ` Arnd Bergmann
2006-08-20 6:31 ` Benjamin Herrenschmidt
2006-08-20 10:03 ` Arnd Bergmann
2006-08-23 21:36 ` Linas Vepstas
2006-08-23 22:03 ` David Miller
2006-08-18 22:23 ` [PATCH 3/6]: powerpc/cell spidernet stop error printing patch Linas Vepstas
2006-08-18 22:25 ` [PATCH 4/6]: powerpc/cell spidernet ethtool -i version number info Linas Vepstas
2006-08-18 22:56 ` Arnd Bergmann
2006-08-18 22:26 ` [PATCH 5/6]: powerpc/cell spidernet bottom half Linas Vepstas
2006-08-18 23:03 ` Arnd Bergmann
2006-08-19 0:56 ` [RFC] HOWTO use NAPI to reduce TX interrupts Arnd Bergmann
2006-08-20 1:31 ` Stephen Hemminger
2006-08-19 11:25 ` Arnd Bergmann [this message]
2006-08-20 17:48 ` [RFC v2] " Arnd Bergmann
2006-08-21 20:40 ` NAPI documentation Stephen Hemminger
2006-08-21 22:05 ` David Miller
2006-08-21 22:09 ` Stephen Hemminger
2006-08-21 22:17 ` David Miller
2006-08-21 23:52 ` [RFC] HOWTO use NAPI to reduce TX interrupts Linas Vepstas
2006-08-21 23:56 ` David Miller
2006-08-22 0:29 ` Roland Dreier
2006-08-22 0:32 ` David Miller
2006-08-23 1:29 ` Shirley Ma
2006-08-23 21:52 ` [PATCH 5/6]: powerpc/cell spidernet bottom half Linas Vepstas
2006-08-18 22:29 ` [PATCH 6/6]: powerpc/cell spidernet refine locking Linas Vepstas
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