![]() | |||||||||||||
Messages in this thread |
Fabio Brugnara <brugnara@itc.it> wrote: > > The problem is related to the use of memory mapped files over a nfs > mounted filesystem. In a rather complex system (speech recognition) that we > developed and use, we need to share large read-only data structures between > different processes, also on several machines. Until a few months ago, we > observed that it was perfectly adequate to just mmap() a file residing on a > particular disk, that machines other as the owner mounted via nfs. This was > very convenient, as we had only a single physical copy of the data > structure, and it did not introduce any significant performance penalty. We > have used this method for years. > Now, after the machines have been upgraded to kernel 2.6.10 from > kernel 2.4.20, something disappointing happens. Everything still works > correctly, but somehow it introduces a massive slowdown of the machines. > While the processes are running, the machines that map the shared file via > nfs (not the one that owns it) report (with "top") a very high usage of > system time (e.g. 50% or more), and also become very unresponsive at the > shell prompt. Could you please generate a kernel profile? - Compile with CONFIG_PROFILING - Start the workload, wait for steady state. - As root, run: #!/bin/sh SM=/boot/System.map TIMEFILE=/tmp/prof.time readprofile -r sleep 10 readprofile -n -v -m $SM | sort -n +2 | tail -40 | tee $TIMEFILE >&2 (make sure that /boot/System.map is from the currently-running kernel) More in Documentation/basic_profiling.txt Even better, learn to drive oprofile. Once it's running properly I usually use this silly script: #!/bin/sh opcontrol --stop opcontrol --shutdown rm -rf /var/lib/oprofile opcontrol --vmlinux=/boot/vmlinux-$(uname -r) opcontrol --start-daemon opcontrol --start sleep 10 opcontrol --stop opcontrol --shutdown opreport -l /boot/vmlinux-$(uname -r) | head -50 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
| Last update: 2005-05-06 13:59 [from the cache] ©2003-2008 | |||||||||||||