Also, that document refers to the old PVFS, not the new code base.
Thanks,
Rob
Murali Vilayannur wrote:
Hi,
Problem with running executables off PVFS volumes is that page-ins of the
text segment will cause a flurry of I/O requests of 4KB/8KB (as the page
size may be) to the servers which is really not optimal and could hence
slow things down for a lot of people.
In PVFS2, we have a readahead mmap cache in the client core daemon which
can be enabled by configure --enable-mmap-racache which will basically
help in such situations by prefetching the entire executable and service
it from client-core cache instead of from servers.
Perhaps that can mitigate this problem a bit..
Hope this helps,
Murali
On Tue, 8 Aug 2006, Mark Bartelt wrote:
Someone forwarded me the following URL ...
http://thunderhead.gsfc.nasa.gov/Users_Guide/PVFS.shtml
... an excerpt from which is appended below. Does this
seem reasonable? I'm a bit puzzled about why running an
executable that happens to live on a PVFS filesystem is
likely to cause much grief. Is it frequent page-ins of
the a.out's text segment, or something else entirely?
(Or for that matter, is the claim below even true?)
=============================================
Can I run my executables from my user directory in
/data1 (on the PVFS server)?
NO, PLEASE DON'T DO THIS! It will cause PVFS to run
painfully slowly for all of the users and the sysadmins
will become quite manic. Be a good neighbor, and run
from home/rhome, please don't run executables from PVFS.
If you decide to run from PVFS anyway, you could correctly
visualize your office as being similar to Frankenstein's
castle being stormed by furious torch-bearing Thunderhead
users and anxious system administrators.
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