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Re: Measure the Accept Queueing Time
- From: Andi Kleen <ak at suse dot de>
- To: systemtap at sources dot redhat dot com
- Date: Fri, 17 Feb 2006 17:22:54 +0100
- Subject: Re: Measure the Accept Queueing Time
- References: <43E28A07.1040604@tamu.edu> <200602171601.36205.ak@suse.de> <20060217161538.GF3170@redhat.com>
On Friday 17 February 2006 17:15, Frank Ch. Eigler wrote:
> Hi -
>
> ak wrote:
> > [...]
> > > But the two probes must have some connection in order for that time
> > > difference to make sense. tid() ?
> >
> > Doesn't work for nested interrupts.
>
> Could you outline a problematic scenario more fully?
interrupt 1
calls function to be measured
startprobe
... function runs....
interrupt 2 from a different device
calls function to be measured again
startprobe nested
... function runs nested ...
endprobe nested
interrupt 2 ends
... function still runs ...
endprobe
x86-64 has a per cpu interrupt nesting count, but even with that
and using (tid, count) as index there are some problems.
I hit this when trying to measure dma_map_sg()
-Andi