Unify KVM kernel-space and user-space code into a single project
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From: Zhang, Yanmin on 25 Mar 2010 05:00 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(a)doppio linux-2.6-tip]$ perf buildid-list | grep libpthread > > 5c68f7afeb33309c78037e374b0deee84dd441f6 /lib64/libpthread-2.10.2.so > > [acme(a)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(a)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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Antoine Martin on 8 Apr 2010 10:30
Avi Kivity wrote: > On 03/24/2010 06:40 PM, Joerg Roedel wrote: >> >>> Looks trivial to find a guest, less so with enumerating (still doable). >>> >> Not so trival and even more likely to break. Even it perf has the pid of >> the process and wants to find the directory it has to do: >> >> 1. Get the uid of the process >> 2. Find the username for the uid >> 3. Use the username to find the home-directory >> >> Steps 2. and 3. need nsswitch and/or pam access to get this information >> from whatever source the admin has configured. And depending on what the >> source is it may be temporarily unavailable causing nasty timeouts. In >> short, there are many weak parts in that chain making it more likely to >> break. >> > > It's true. If the kernel provides something, there are fewer things > that can break. But if your system is so broken that you can't resolve > uids, fix that before running perf. Must we design perf for that case? uid to username can fail when using chroots, or worse point to an incorrect location (and yes, I do use this) Sorry if this has been covered / discussion has moved on. Just catching up with the 500+ messages in my inbox.. Antoine > > After all, 'ls -l' will break under the same circumstances. It's hard > to imagine doing useful work when that doesn't work. > >> A kernel-based approach with /proc/<pid>/kvm does not have those issues >> (and to repeat myself, it is independent from the userspace being used). >> > > It has other issues, which are IMO more problematic. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |