Date: Fri, 09 Feb 2001 08:15:47 -0800 From: Julian Elischer <julian@elischer.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: freebsd-current@FreeBSD.ORG, Dag-Erling Smorgrav <des@ofug.org>, Josef Karthauser <joe@tao.org.uk>, Robert Watson <rwatson@FreeBSD.ORG>, Brian Somers <brian@Awfulhak.org>, Bruce Evans <bde@zeta.org.au>, freebsd-hackers@FreeBSD.ORG Subject: Re: What's changed recently with vmware/linuxemu/file I/O Message-ID: <3A8417B3.126F47AB@elischer.org> References: <xzpsnlqmh0o.fsf@flood.ping.uio.no> <Pine.NEB.3.96L.1010207220443.19807J-100000@fledge.watson.org> <20010208113519.A789@tao.org.uk> <3A828C2C.F7CDA809@elischer.org> <xzp4ry5gve0.fsf@flood.ping.uio.no> <14979.29437.518299.842853@grasshopper.cs.duke.edu> <14980.2381.849005.313177@grasshopper.cs.duke.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
Andrew Gallatin wrote: > > Andrew Gallatin writes: > > > > Dag-Erling Smorgrav writes: > > > Julian Elischer <julian@elischer.org> 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: gallatin@cs.duke.edu > Department of Computer Science Phone: (919) 660-6590 -- __--_|\ Julian Elischer / \ julian@elischer.org ( OZ ) World tour 2000-2001 ---> X_.---._/ v To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3A8417B3.126F47AB>