[Pvfs2-users] running executables from PVFS filesystems

[Rob Ross]

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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>>
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