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.
Drew
------------------------------------------------------------------------------
Andrew Gallatin, Sr Systems Programmer http://www.cs.duke.edu/~gallatin
Duke University Email: [EMAIL PROTECTED]
Department of Computer Science Phone: (919) 660-6590
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-current" in the body of the message
