Andrew Gallatin writes:
 > Dag-Erling Smorgrav writes:
 >  > Julian Elischer <[EMAIL PROTECTED]> writes:
 >  > > I believe that vmware mmaps a region of memory and then somehow syncs 
 >  > > it to disk. (It is certainly doing something like it here).
 >  > 
 >  > Theory: VMWare mmaps a region of memory corresponding to the virtual
 >  > machine's "physical" RAM, then touches every page during startup.
 >  > Unless some form of clustering is done, this causes 16384 write
 >  > operations for a 64 MB virtual machine...
 >  > 
 > Pretty much.  But the issue is that this should never hit the disk
 > unless we're under memory pressure because it is mapped MAP_NOSYNC
 > (actually the file is unlinked prior to the mmap() and a heuristic in
 > vm_mmap() detects this and sets MAP_NOSYNC).

I take it back.  At least with the latest version of vmware, it is
apparently not mapped MAP_NOSYNC.  I think they've moved from
mmap'ing a file in $TMPDIR to just using the CONFIG.std save/resume
file.  Perhaps this is only if you have resumed from a suspended
state... I haven't checked that out yet.

At any rate, hacking linux_mmap to ad MAP_NOSYNC to mmaped files, in
combination with yesterdays patch, appears to improve
perf. considerably. 


Andrew Gallatin, Sr Systems Programmer
Duke University                         Email: [EMAIL PROTECTED]
Department of Computer Science          Phone: (919) 660-6590

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