On Tuesday 08 September 2009, Noam Rathaus wrote: > So I am stuck > > Grrr > > Anyone with ideas on how I can understand why "my packages" are causing > issues, while apparently, "perl-provided" packages such as LWP::UserAgent > dont? http://www.gksoft.com/a/fun/catch-lion.html
> > On Tue, Sep 8, 2009 at 5:58 PM, Shachar Shemesh <shac...@shemesh.biz> wrote: > > Noam Rathaus wrote: > > > > The only obvious one is that read() shown under strace, takes a > > significant more time on the new machine than the old one > > > > You can split the difference between the platforms into three groups: > > Time spent in the kernel (0.032 seconds) > > Time spent in userspace (7.761 seconds) > > Time spent sleeping or otherwise scheduled out (7.287 seconds) > > > > strace -c goes a long way, and works very hard, to show us information > > that is not useful to us. It counts CPU time spent in system calls, not > > actual wall time. What may provide a more useful output in this case is > > -T, which will also count time in which the process was sleeping inside a > > system call (which accounts for about half the slowdown). > > > > The second half of the slowdown, the one done in user space, is more > > difficult to trace without the sources (i.e. - the perl sources). > > valgrind has a module for detecting what causes a slowdown, but I doubt > > Noam wants to start analyzing perl to figure out what the different areas > > actually mean. > > > > > > Shachar > > > > On Tue, Sep 8, 2009 at 5:43 PM, Shachar Shemesh <shac...@shemesh.biz>wrote: > >> Noam Meltzer wrote: > >> > >> the time output does looks like you have higher cpu usage for some > >> reason, so i agree with Shachar on this. > >> > >> you can also try to pinpoint the place the cpu is spent. > >> strace and/or ltrace with the '-f -c' flags can help. > >> > >> I'm not sure about ltrace, but strace will not help. Most of the time > >> is spent in user space, not in the kernel. > >> > >> Strace may help if the problem is time spent in another process (i.e. - > >> while the main process is sleeping), but it seems Noam has already tried > >> that one and failed to spot any obvious candidates. > >> > >> Shachar > >> > >> On Tue, Sep 8, 2009 at 5:24 PM, Shachar Shemesh <shac...@shemesh.biz>wrote: > >>> Noam Rathaus wrote: > >>> > >>> I know the time difference doesn't look too bad, but take a bigger code > >>> set: > >>> > >>> Fast: > >>> real 0m1.682s > >>> user 0m1.584s > >>> sys 0m0.064s > >>> > >>> Slow: > >>> real 0m16.730s > >>> user 0m9.345s > >>> sys 0m0.096s > >>> > >>> These times spell "CPU intensive". Does your library do anything > >>> special? If you try to import a dummy library, does this still happen? > >>> > >>> Shachar > >>> > >>> -- > >>> Shachar Shemesh > >>> Lingnu Open Source Consulting Ltd.http://www.lingnu.com > >> > >> -- > >> Shachar Shemesh > >> Lingnu Open Source Consulting Ltd.http://www.lingnu.com > > > > -- > > Shachar Shemesh > > Lingnu Open Source Consulting Ltd.http://www.lingnu.com _______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
