Messages in this thread | | | From | zanussi@us ... | Date | Thu, 22 Jul 2004 15:47:03 -0500 | Subject | LTT user input |
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Hi,
One of the things people mentioned wanting to see during Karim's LTT talk at the Kernel Summit was cases where LTT had been useful to real users. Here are some examples culled from the ltt/ltt-dev mailing lists:
http://www.listserv.shafik.org/pipermail/ltt/2004-July/000631.html http://www.listserv.shafik.org/pipermail/ltt/2004-July/000630.html http://www.listserv.shafik.org/pipermail/ltt/2004-July/000629.html http://www.listserv.shafik.org/pipermail/ltt/2004-March/000559.html http://www.listserv.shafik.org/pipermail/ltt/2003-April/000341.html http://www.listserv.shafik.org/pipermail/ltt/2002-April/000199.html http://www.listserv.shafik.org/pipermail/ltt/2001-December/000118.html http://www.listserv.shafik.org/pipermail/ltt/2001-July/000064.html http://www.listserv.shafik.org/pipermail/ltt/2001-April/000020.html
As with most other tools, we don't tend to hear from users unless they have problems with the tool. :-( LTT has also been picked up by Debian, SuSE, and MontaVista - maybe they have user input that we don't get to see as well...
Another thing that came up was the impression that the overhead of tracing is too high. I'm not sure where the number mentioned (5%) came from, but the peformance numbers we generated for the relayfs OLS paper last year, using LTT as a test case, were 1.40% when tracing everything but having the userspace daemon discard the transferred data and 2.01% when tracing everything and having the daemon write all data to disk.
The test system was a 4-way 700MHz Pentium III system, tracing all event types (syscall entry/exit, interrupt entry/exit, trap entry/exit, scheduling changes, kernel timer, softirq, process, filesystem, memory management, socket, ipc, network device). For each number, we ran 10 kernel compiles while tracing. Each 10-compile run generated about 200 million events comprising about 2 gigabytes.
Tom
-- Regards,
Tom Zanussi <zanussi@us.ibm.com> IBM Linux Technology Center/RAS
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