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Date: Mon, 4 Feb 2002 13:16:51 +0100 (CET)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: <mingo@elte.hu>
To: Steffen Persvold <sp@scali.com>
Cc: Jens Axboe <axboe@suse.de>, lkml <linux-kernel@vger.kernel.org>
Subject: Re: Short question regarding generic_make_request()
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On Mon, 4 Feb 2002, Steffen Persvold wrote:

> [root@damd1 root]# ping sci4
> PING sci4 (192.168.4.4) from 192.168.4.3 : 56(84) bytes of data.
> 64 bytes from sci4 (192.168.4.4): icmp_seq=0 ttl=255 time=238 usec

> For simplicity I'll say ~200usec. When I change the receive handler
> from a tasklet to a kernel thread, the numbers look like this :
>
> [root@damd1 root]# ping sci4
> PING sci4 (192.168.4.4) from 192.168.4.3 : 56(84) bytes of data.
> 64 bytes from sci4 (192.168.4.4): icmp_seq=0 ttl=255 time=4.215 msec
> 64 bytes from sci4 (192.168.4.4): icmp_seq=1 ttl=255 time=5.728 msec

this shows some sort of wakeup or softirq handling irregularity. A number
of softirq latency bugs were fixed, i'd suggest to try this with any
recent kernel (or recent errata kernel rpms).

	Ingo

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