On Fri, Jul 1, 2022 at 4:53 PM Marc-André Lureau <marcandre.lur...@gmail.com>
wrote:
> Hi
>
> On Fri, Jul 1, 2022 at 7:11 AM zhenwei pi <pizhen...@bytedance.com> wrote:
>
>> A vCPU thread always reaches 100% utilization when:
>> - guest uses idle=poll
>> - disable HLT vm-exit
>> - enable MWAIT
>>
>> Add new guest agent command 'guest-get-cpustats' to get guest CPU
>> statistics, we can know the guest workload and how busy the CPU is.
>>
>> Signed-off-by: zhenwei pi <pizhen...@bytedance.com>
>> ---
>> qga/commands-posix.c | 72 ++++++++++++++++++++++++++++++++++++++++++++
>> qga/commands-win32.c | 6 ++++
>> qga/qapi-schema.json | 49 ++++++++++++++++++++++++++++++
>> 3 files changed, 127 insertions(+)
>>
>> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
>> index 0469dc409d..2847023876 100644
>> --- a/qga/commands-posix.c
>> +++ b/qga/commands-posix.c
>> @@ -2893,6 +2893,73 @@ GuestDiskStatsInfoList
>> *qmp_guest_get_diskstats(Error **errp)
>> return guest_get_diskstats(errp);
>> }
>>
>> +GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
>> +{
>> + GuestCpuStatsList *head = NULL, **tail = &head;
>> + const char *cpustats = "/proc/stat";
>> + FILE *fp;
>> + size_t n;
>> + char *line = NULL;
>> +
>> + fp = fopen(cpustats, "r");
>> + if (fp == NULL) {
>> + error_setg_errno(errp, errno, "open(\"%s\")", cpustats);
>> + return NULL;
>> + }
>> +
>> + while (getline(&line, &n, fp) != -1) {
>> + GuestCpuStats *cpustat = NULL;
>> + int i;
>> + unsigned long user, system, idle, iowait, irq, softirq, steal,
>> guest;
>> + unsigned long nice, guest_nice;
>> + char name[64];
>> +
>> + i = sscanf(line, "%s %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
>> + name, &user, &nice, &system, &idle, &iowait, &irq,
>> &softirq,
>> + &steal, &guest, &guest_nice);
>> +
>> + /* drop "cpu 1 2 3 ...", get "cpuX 1 2 3 ..." only */
>> + if (strncmp(name, "cpu", 3) || (name[3] == '\0')) {
>>
>
> For extra safety, check !name as well
>
>
>> + continue;
>> + }
>> +
>>
>
> if i < 5, I guess you should warn and continue
>
Why should we skip lines where i < 5? We have CPU time of user and system
modes, I think this is good for reporting.
>
>
>> + cpustat = g_new0(GuestCpuStats, 1);
>> + cpustat->cpu = atoi(&name[3]);
>> + cpustat->has_user = true;
>> + cpustat->user = user * 10;
>>
>
> proc(5) says that the value is given "in units of USER_HZ (1/100ths of a
> second on most architectures, use sysconf(_SC_CLK_TCK) to obtain the right
> value)", so we should adjust this code if we want to return correctly in ms.
>
>
>> + cpustat->has_system = true;
>> + cpustat->system = system * 10;
>> + cpustat->has_idle = true;
>> + cpustat->idle = idle * 10;
>> +
>> + /* Linux version >= 2.6 */
>>
>
> That's pretty old now (2003), not sure anyone would care about that
> comment, but np ;)
>
>
>> + if (i > 5) {
>> + cpustat->has_iowait = true;
>> + cpustat->iowait = iowait * 10;
>> + cpustat->has_irq = true;
>> + cpustat->irq = irq * 10;
>> + cpustat->has_softirq = true;
>> + cpustat->softirq = softirq * 10;
>> + }
>> +
>> + if (i > 8) {
>> + cpustat->has_steal = true;
>> + cpustat->steal = steal * 10;
>> + }
>> +
>> + if (i > 9) {
>> + cpustat->has_guest = true;
>> + cpustat->guest = guest * 10;
>> + }
>> +
>> + QAPI_LIST_APPEND(tail, cpustat);
>> + }
>> +
>> + free(line);
>> + fclose(fp);
>> + return head;
>> +}
>> +
>> #else /* defined(__linux__) */
>>
>> void qmp_guest_suspend_disk(Error **errp)
>> @@ -3247,6 +3314,11 @@ GuestDiskStatsInfoList
>> *qmp_guest_get_diskstats(Error **errp)
>> return NULL;
>> }
>>
>> +GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
>> +{
>> + error_setg(errp, QERR_UNSUPPORTED);
>> + return NULL;
>> +}
>>
>> #endif /* CONFIG_FSFREEZE */
>>
>> diff --git a/qga/commands-win32.c b/qga/commands-win32.c
>> index 36f94c0f9c..7ed7664715 100644
>> --- a/qga/commands-win32.c
>> +++ b/qga/commands-win32.c
>> @@ -2543,3 +2543,9 @@ GuestDiskStatsInfoList
>> *qmp_guest_get_diskstats(Error **errp)
>> error_setg(errp, QERR_UNSUPPORTED);
>> return NULL;
>> }
>> +
>> +GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
>> +{
>> + error_setg(errp, QERR_UNSUPPORTED);
>> + return NULL;
>> +}
>> diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
>> index 9fa20e791b..4859c887b2 100644
>> --- a/qga/qapi-schema.json
>> +++ b/qga/qapi-schema.json
>> @@ -1576,3 +1576,52 @@
>> { 'command': 'guest-get-diskstats',
>> 'returns': ['GuestDiskStatsInfo']
>> }
>> +
>> +##
>> +# @GuestCpuStats:
>> +#
>> +# Get statistics of each CPU in millisecond.
>> +#
>> +# @cpu: CPU index in guest OS
>> +#
>> +# @user: CPU time of user mode
>>
>
> "Time spent in user mode." is more understandable (from man proc(5))
>
> Same for the other descriptions.
>
> +#
>> +# @system: CPU time of system mode
>> +#
>> +# @idle: CPU time of idle state
>> +#
>> +# @iowait: CPU time waiting IO
>> +#
>> +# @irq: CPU time of hardware interrupt
>> +#
>> +# @softirq: CPU time of soft interrupt
>> +#
>> +# @steal: CPU time stolen by host
>> +#
>> +# @guest: CPU time of running guest mode
>>
>
> Why not "guest_nice" ?
>
> Do we expect this struct to be equally meaningful for other OSes?
> Otherwise, I would suggest to make a "linux" variant, perhaps.
>
The /proc/stat is very Linux-specific, so I think if we implement something
similar for Windows, we have another structure.
>
> +#
>> +# Since: 7.1
>> +##
>> +{ 'struct': 'GuestCpuStats',
>> + 'data': {'cpu': 'int',
>> + '*user': 'uint64',
>> + '*system': 'uint64',
>> + '*idle': 'uint64',
>> + '*iowait': 'uint64',
>> + '*irq': 'uint64',
>> + '*softirq': 'uint64',
>> + '*steal': 'uint64',
>> + '*guest': 'uint64'
>> + } }
>> +
>> +##
>> +# @guest-get-cpustats:
>> +#
>> +# Retrieve information about CPU stats.
>> +# Returns: List of CPU stats of guest.
>> +#
>> +# Since: 7.1
>> +##
>> +{ 'command': 'guest-get-cpustats',
>> + 'returns': ['GuestCpuStats']
>> +}
>> --
>> 2.20.1
>>
>>
>>
>
> --
> Marc-André Lureau
>
