From: David Miller <davem@davemloft.net>
To: jgarzik@pobox.com
Cc: yang.shi@windriver.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Improvev netconsole support for RTL8139 NIC driver
Date: Tue, 25 Mar 2008 20:30:43 -0700 (PDT) [thread overview]
Message-ID: <20080325.203043.196469543.davem@davemloft.net> (raw)
In-Reply-To: <47E9BF7B.3030003@pobox.com>
From: Jeff Garzik <jgarzik@pobox.com>
Date: Tue, 25 Mar 2008 23:14:03 -0400
> David Miller wrote:
> > From: Jeff Garzik <jgarzik@pobox.com>
> > Date: Tue, 25 Mar 2008 22:23:24 -0400
> >
> >> This is bogus -- you should never need to slow down the hot path in such
> >> a way.
> >
> > Slow down in what way? Even on x86 saving the flags is just
> > about as expensive as a plain sti/cli.
>
> Replacing spin_lock() [current 8139too.c] with spin_lock_irqsave()
> results in a larger interrupt handler... more CPU instructions for the
> same result.
Jeff, please be realistic.
These interrupt handlers about to do a PIO on a status register, which
will consume on the order of a few hundred cpu cycles.
Counting an I-cache line or two, or 18 cycles here or there,
is immaterial by comparison.
next prev parent reply other threads:[~2008-03-26 3:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-26 2:12 [PATCH] Improvev netconsole support for RTL8139 NIC driver yshi
2008-03-26 2:23 ` Jeff Garzik
2008-03-26 2:38 ` yshi
2008-03-26 2:42 ` David Miller
2008-03-26 2:52 ` yshi
2008-03-26 3:14 ` Jeff Garzik
2008-03-26 3:14 ` Jeff Garzik
2008-03-26 3:30 ` David Miller [this message]
2008-03-26 3:39 ` Jeff Garzik
2008-03-26 3:48 ` Jeff Garzik
2008-03-26 3:53 ` David Miller
2008-03-26 4:32 ` Jeff Garzik
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