On Thu, Mar 03, 2011 at 06:26:19PM +0800, Daniel Veillard wrote: > This patch set main goal is to allow dumping > of full debug informations for operations occuring > in libvirt daemon before a crash. > The principle is to save all logs to a round-robbin memory > buffer (which we already do, except we never use that > buffer), save the general daemon logs to a libvirtd.log > file for which we keep an open descriptor, and upon > reception of a fatal signal, save the memory buffer > directly to the file descriptor and fsync it. > > There is quite a few remarks about this, we already have > that buffer but we don't log everything in, only what's > output, that's what patch 1 changes, then we need to > provide a function to dump this, so there is a new internal > API for it. We also need to be cautious about what > system call we operate from the signal handler, but > basically we should limit ourselves here to write/fsync and > sigaction which are safe there dixit POSIX. > > Something like killall -USR2 libvirtd allows to see the > kind of output one get, an idle libvirtd is quiet, but > handle/timer/fdpolls tend to be very verbose, maybe we need > an intermediate debug level, but that would also impact the > API. Maybe now that this part is well debugged some of those > could be suppressed or commented off. > > Also the buffer is a statically allocated 64KB, maybe this > could be made more flexible but IMHO that's not fundamental.
64 KB is unlikely to be sufficiently large if libvirt is running under RHEV with moderate load. With a fairly strict log filter of '1:libvirt 1:util 1:qemu' RHEV generates > 300 MB of logs in ~10 minutes. This works out at approx 512 KB per second so a 64 KB buffer will only capture 125 milliseconds at that log filter level, and far far less if collecting full debug logs Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
