linux-kernel - Re: [PATCH] Improvev netconsole support for RTL8139 NIC driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20080325.203043.196469543.davem@davemloft.net>
Date:	Tue, 25 Mar 2008 20:30:43 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jgarzik@...ox.com
Cc:	yang.shi@...driver.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Improvev netconsole support for RTL8139 NIC driver

From: Jeff Garzik <jgarzik@...ox.com>
Date: Tue, 25 Mar 2008 23:14:03 -0400

> David Miller wrote:
> > From: Jeff Garzik <jgarzik@...ox.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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/