if the processes were working on different files it is likely because
the resulting i/o pattern is more sequential.
Murali Vilayannur wrote:
Hi Phil,
I did find one odd result, although it is somewhat unrelated. In an
earlier email on this topic I mentioned that I was able to find a
temporary workaround for the bug by setting PVFS2_BUFMAP_DESC_COUNT to
1, which limits pvfs2-client-core to only performing one I/O operation
at a time. A surprising side effect of this was that (regardless of the
flow post order) this configuration substantially increased performance
for a 5 process I/O benchmark.
In this particular test there are 5 processes, each both reading and
writing large files on the same PVFS2 file system. The results are
counter-intuitive, because the whole point of having multiple buffers
was to allow more concurrent activity when multiple processes perform
I/O. However, the test went faster when only one I/O operation was
allowed to proceed at a time.
Wow.. That is interesting indeed. I will see if I can trigger this
behavior as well..Thanks for the info!
Murali
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