Date: Mon, 16 Sep 2002 12:29:51 +0200 (CEST) From: Harti Brandt <brandt@fokus.gmd.de> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Bruce Evans <bde@zeta.org.au>, Josef Karthauser <joe@FreeBSD.ORG>, "David O'Brien" <obrien@FreeBSD.ORG>, <cvs-committers@FreeBSD.ORG>, <cvs-all@FreeBSD.ORG> Subject: Re: cvs commit: src/sys/kern kern_timeout.c Message-ID: <20020916122355.N92332-100000@beagle.fokus.gmd.de> In-Reply-To: <13645.1032171121@critter.freebsd.dk>
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On Mon, 16 Sep 2002, Poul-Henning Kamp wrote:
PK>In message <20020916195344.S6593-100000@gamplex.bde.org>, Bruce Evans writes:
PK>
PK>>> > Sep 15 19:40:26 kernel: Expensive timeout(9) function: 0xc65dfc80(0xc659f000) 0.008711721
PK>>> > Sep 15 19:40:26 kernel: Expensive timeout(9) function: 0xc65dfc80(0xc659f000) 0.001068850
PK>>
PK>
PK>I have seen other ${netcard}_tick() do the same. I wonder if the
PK>1 second timers in network drivers should be moved from timeout(9)
PK>to a kernel thread doing just that: polling net drivers 1/sec.
I just working on xl_stats_update which takes between 7.5 and 20 msecs.
This is far to long for my HZ=10000 setup.
PK>>8 msec
PK>>is a huge bite out of the 10 msec between softclock for the default
PK>>HZ, and huger for larger HZ. softclock() expects to run multiple
PK>>timeout routines and shouldn't take more than 1% of the CPU(s) altogether,
PK>>but 8 msec per second is already 0.8% of 1 CPU for just 1 device.
PK>
PK>But couldn't some of this be due to evil DELAY() or locking in the
PK>in the timeout routine ? In that case it's only the duration, not
PK>the CPU usage which is .8% ?
In case of the xl driver it is a problem with DELAY(). One xl_mii_readreg
needs 184 DELAY(1) calls, each of which takes around 9usecs. The mii_tick
needs several readregs. Just for testing I have converted all these DELAYs
to use busy wait on the TSC. This cuts down the readreg() time to
350usecs!
IMHO all those status update stuff should rather run from a kernel thread.
harti
--
harti brandt, http://www.fokus.gmd.de/research/cc/cats/employees/hartmut.brandt/private
brandt@fokus.gmd.de, brandt@fokus.fhg.de
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