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    SubjectRe: [RFC] Unify KVM kernel-space and user-space code into a single project
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    On Wed, 2010-03-24 at 20:20 +0200, Avi Kivity wrote:
    > On 03/24/2010 07:47 PM, Arnaldo Carvalho de Melo wrote:
    > > Em Wed, Mar 24, 2010 at 06:09:30PM +0200, Avi Kivity escreveu:
    > >
    > >> Doesn't perf already has a dependency on naming conventions for finding
    > >> debug information?
    > >>
    > > It looks at several places, from most symbol rich (/usr/lib/debug/, aka
    > > -debuginfo packages, where we have full symtabs) to poorest (the
    > > packaged binary, where we may just have a .dynsym).
    > >
    > > In an ideal world, it would just get the build-id (a SHA1 cookie that is
    > > in an ELF session inserted in every binary (aka DSOs), kernel module,
    > > kallsyms or vmlinux file) and use that to look first in a local cache
    > > (implemented in perf for a long time already) or in some symbol server.
    > >
    > > For instance, for a random perf.data file I collected here in my machine
    > > I have:
    > >
    > > [acme@doppio linux-2.6-tip]$ perf buildid-list | grep libpthread
    > > 5c68f7afeb33309c78037e374b0deee84dd441f6 /lib64/libpthread-2.10.2.so
    > > [acme@doppio linux-2.6-tip]$
    > >
    > > So I don't have to access /lib64/libpthread-2.10.2.so directly, nor some
    > > convention to get a debuginfo in a local file like:
    > >
    > > /usr/lib/debug/lib64/libpthread-2.10.2.so.debug
    > >
    > > Instead the tools look at:
    > >
    > > [acme@doppio linux-2.6-tip]$ l ~/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6
    > > lrwxrwxrwx 1 acme acme 73 2010-01-06 18:53 /home/acme/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6 -> ../../lib64/libpthread-2.10.2.so/5c68f7afeb33309c78037e374b0deee84dd441f6*
    > >
    > > To find the file for that specific build-id, not the one installed in my
    > > machine (or on the different machine, of a different architecture) that
    > > may be completely unrelated, a new one, or one for a different arch.
    > >
    >
    > Thanks. I believe qemu could easily act as a symbol server for this use
    > case.


    I spent a couple of days to investigate why sshfs/fuse doesn't work well with
    procfs and sysfs. Just after my patch against fuse is ready almost, I found
    fuse already supports such access by direct I/O. With parameter -o direct_io,
    it could work well.

    Here is an example to mount / from a guest os.
    #sshfs -p 5551 -o direct_io localhost:/ guestmount

    We can read files and write files if permission is ok.

    I will go ahead to support multiple guest os instance statistics parsing.

    Yanmin




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