On Wed, Mar 05, 2014 at 05:53:48PM -0700, Eric Blake wrote:
On 03/05/2014 10:53 AM, Daniel P. Berrange wrote:
Extracting capabilities from QEMU takes a notable amount of time when all QEMU binaries are installed. Each system emulator needs about 200-300ms multiplied by 26 binaries == ~5-8 seconds.
This change causes the QEMU driver to save an XML file containing the content of the virQEMUCaps object instance in the cache dir eg /var/cache/libvirt/qemu/capabilities/$SHA256(binarypath).xml or $HOME/.cache/libvirt/qemu/cache/capabilities/$SHA256(binarypath).xml
We attempt to load this and only if it fails, do we fallback to probing the QEMU binary. The timestamp of the file is compared to the timestamp of the QEMU binary and discarded if the QEMU binary is newer.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com> --- src/qemu/qemu_capabilities.c | 412 ++++++++++++++++++++++++++++++++++++++++++- src/qemu/qemu_capabilities.h | 2 + src/qemu/qemu_driver.c | 1 + 3 files changed, 407 insertions(+), 8 deletions(-)
@@ -44,6 +45,7 @@ #include <unistd.h> #include <sys/wait.h> #include <stdarg.h> +#include <utime.h>
<utime.h> (and the utime() function) is deprecated by POSIX and therefore no longer portable because it corrupts sub-second timestamps. Better is to use gnulib's utimensat (or futimens). But what timestamps do we actually have to munge?
+ + ut.actime = qemuCaps->mtime; + ut.modtime = qemuCaps->mtime; + if (utime(filename, &ut) < 0) { + virReportSystemError(errno, + _("Failed to set mtime on '%s' for '%s'"), + filename, qemuCaps->binary);
Why not just store the qemu binary timestamp in the XML, rather than playing games with the mtime of the xml file?
I wanted to be able to detect out of date cache files without having to go through parsing them. Regards, 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 :|