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@xxxxxxxxxx>
> ---
> 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?
> +
> + /* Discard if cache is older that QEMU binary */
> + /* XXX must also compare to libvirtd timestamp */
> + if (sb.st_mtime < qemuCaps->mtime) {
This ignores subsecond timestamps; you may want to use gnulib's
stat-time module to do a more accurate check.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
Attachment:
signature.asc
Description: OpenPGP digital signature
-- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list