Messages in this thread | | | Date | Tue, 25 Mar 2008 20:30:43 -0700 (PDT) | Subject | Re: [PATCH] Improvev netconsole support for RTL8139 NIC driver | From | David Miller <> |
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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.
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