[PATCH v2 2/2] Use virProcessGetStat

[Martin Kletzander]

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.

Thanks,
Martin

>
>Regards,
>Daniel
>-- 
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>
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