This is the mail archive of the
systemtap@sourceware.org
mailing list for the systemtap project.
Re: Why systemtap loses events and what can be done about it?
- From: "Frank Ch. Eigler" <fche at redhat dot com>
- To: ååå <zzh at ncic dot ac dot cn>
- Cc: systemtap at sources dot redhat dot com
- Date: Thu, 30 Aug 2007 23:58:40 -0400
- Subject: Re: Why systemtap loses events and what can be done about it?
- References: <20070830132846.GA20477@redhat.com> <CC992CB620BE49C98F14E8285A4E2D98@ncicdcos>
Hi -
> <zzh@ncic.ac.cn> wrote:
> [...] To make my question clear, I have to introduce my work in
> more detail. I am trying to use systemtap to analyze the
> communication pattern of internet service. One basic issue is to
> correlate every pair of tcp_sendmsg and tcp_recvmsg.
(For what it's worth, there may not be a one-to-one correlation,
considering signals, packet loss, buffered delivery, ...)
> Usually I will run a workload to emulate 100-200 clients explore the
> web site simultaneously. In the workload of 200 clients, staprun
> often displays the warning messages about skipped probes(Why?).
I'd have to see your script to give a better guess. return probes
have some dynamic resource constraints that can cause a skip; normal
probes skip in only a few cases (e.g., reentrancy, but that's unlikely
here).
> And in the workload of 100 clients, no warning occurred, but
> sometimes I find some events failed to be recorded. [...]
It is possible that there are some bugs in the system someplace. It
is possible that the skipped probes account for the missing events.
- FChE