Andrew Gallatin wrote:
>
> 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.
I don't like the sound of that hack..
are they doing something in Linux to tell Linux to not sync it?
I nkow it's gross but could we only do that hack if it'a vmware?
(probably should be on -emulation)
>
> 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
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