Hello All,
I have a non iteractive, java application that uses 10 threads and does
some work which consists mostly of reads. I am using the 1.3.1 JVM.
I ran this test on both RHEL3.0 (AS) and RHEL4.0 (AS) with similar
machine configuration and I noticed that on RHEL4.0 it seems to be doing
a lot more context switching.
Since I wasnt sure if it was related to the JVM+kernel, I tried to
change the kernel version to the 2.4.19 by using LD_ASSUME_KERNEL env
variable, but even then on RHEL4, it didnt make any noticeable difference.
I have the following questions. (I am not familar with linux internals,
so sorry if these sound naive).
1)When checking vmstat, I also noticed the following difference in the
memory buff and memory cache counters.
vmstat mem buff mem cache
RHEL4.0 35508 155852
RHEL3.0 75032 513936
Why is it so different ?
2) why are there so many Context switching (CS) happening, is it becasue
2.6 kernel is preemptive, or does the Red hat distribution has some
other advanced scheduling algorithms that is causing it. If so, is there
someway to increase the timeslice on the fly ?
3) changing kernel to 2.4 by using LD_ASSUME_KERNEL - why does that not
help if it is case of just the 2.6 kernel behavior
Both machines have similar configurations and has hyperthreading enabled
with 4 logical CPUs.
RHEL3.0 kernel - is 2.4.21-15.ELsmp #1 SMP, threading is NPTL 0.6
RHEL4.0 kernel is 2.6.9-5.ELsmp #1 SMP, getconf
GNU_LIBPTHREAD_VERSION is NPTL 2.3.4
I searched the archives for this list but didnt find any relevant
info. I'd appreciate any suggestions/pointers/help.
Many Thanks,
Sunitha.
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