[PATCH v2 2/2] Use virProcessGetStat

[Daniel P. Berrangé]

On Mon, Nov 22, 2021 at 10:34:38AM +0100, Martin Kletzander wrote:
> On Mon, Nov 22, 2021 at 09:18:41AM +0000, Daniel P. Berrangé wrote:
> > On Sun, Nov 21, 2021 at 12:04:26AM +0100, Martin Kletzander wrote:
> > > This eliminates one incorrect parsing implementation.
> > 
> > Please explain what was being done wrongly / what was the
> > effect of the bug ?
> > 
> 
> One of the implementations was just looking for first closing
> parenthesis to find the end of the command name, which should be done by
> looking at the _last_ closing parenthesis.  This might fail in a very
> small corner case which is tested for in the first patch.  But you are
> right, I should add this to the commit message.  Will do in v3.
> 
> > > 
> > > Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> > > ---
> > >  src/qemu/qemu_driver.c | 33 ++++++-----------------------
> > >  src/util/virprocess.c  | 48 ++++++------------------------------------
> > >  2 files changed, 12 insertions(+), 69 deletions(-)
> > > 
> > > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > > index d954635dde2a..0468d6aaf314 100644
> > > --- a/src/qemu/qemu_driver.c
> > > +++ b/src/qemu/qemu_driver.c
> > > @@ -1399,36 +1399,17 @@ qemuGetSchedInfo(unsigned long long *cpuWait,
> > > 
> > >  static int
> > >  qemuGetProcessInfo(unsigned long long *cpuTime, int *lastCpu, long *vm_rss,
> > > -                   pid_t pid, int tid)
> > > +                   pid_t pid, pid_t tid)
> > >  {
> > > -    g_autofree char *proc = NULL;
> > > -    FILE *pidinfo;
> > > +    g_auto(GStrv) proc_stat = virProcessGetStat(pid, tid);
> > >      unsigned long long usertime = 0, systime = 0;
> > >      long rss = 0;
> > >      int cpu = 0;
> > > 
> > > -    /* In general, we cannot assume pid_t fits in int; but /proc parsing
> > > -     * is specific to Linux where int works fine.  */
> > > -    if (tid)
> > > -        proc = g_strdup_printf("/proc/%d/task/%d/stat", (int)pid, tid);
> > > -    else
> > > -        proc = g_strdup_printf("/proc/%d/stat", (int)pid);
> > > -    if (!proc)
> > > -        return -1;
> > > -
> > > -    pidinfo = fopen(proc, "r");
> > > -
> > > -    /* See 'man proc' for information about what all these fields are. We're
> > > -     * only interested in a very few of them */
> > > -    if (!pidinfo ||
> > > -        fscanf(pidinfo,
> > > -               /* pid -> stime */
> > > -               "%*d (%*[^)]) %*c %*d %*d %*d %*d %*d %*u %*u %*u %*u %*u %llu %llu"
> > > -               /* cutime -> endcode */
> > > -               "%*d %*d %*d %*d %*d %*d %*u %*u %ld %*u %*u %*u"
> > > -               /* startstack -> processor */
> > > -               "%*u %*u %*u %*u %*u %*u %*u %*u %*u %*u %*d %d",
> > > -               &usertime, &systime, &rss, &cpu) != 4) {
> > > +    if (virStrToLong_ullp(proc_stat[13], NULL, 10, &usertime) < 0 ||
> > > +        virStrToLong_ullp(proc_stat[14], NULL, 10, &systime) < 0 ||
> > > +        virStrToLong_l(proc_stat[23], NULL, 10, &rss) < 0 ||
> > > +        virStrToLong_i(proc_stat[38], NULL, 10, &cpu) < 0) {
> > 
> > Since you're adding a formal API, I think we'd benefit from
> > constants for these array indexes in virprocess.h
> > 
> 
> I was thinking about that and also tried figuring out how to encode the
> proper field types in the header file.  But since we are not doing lot
> of /proc/*/stat parsing in our codebase I though that would be an
> overkill.  I'll add at least the constants.

BTW ,didn't mean we need constants for all 40+ fields - just the ones
we actually use.

Regards,
Daniel
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