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. > _______________________________________________ > Pvfs2-users mailing list > [email protected] > http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users > > _______________________________________________ Pvfs2-users mailing list [email protected] http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users
