[PATCH v4 2/3] util: Add virHostCPUGetHaltPollTime

[Michal Prívozník]

On 7/22/21 10:05 AM, Yang Fei wrote:
> Add helper function virHostCPUGetHaltPollTime to obtain halt polling
> time. If the kernel support halt polling time statistic, and mount
> debugfs. This function will take effect on KVM VMs.
> 
> Signed-off-by: Yang Fei <yangfei85 at huawei.com>
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virhostcpu.c    | 39 +++++++++++++++++++++++++++++++++++++++
>  src/util/virhostcpu.h    |  4 ++++
>  3 files changed, 44 insertions(+)
> 

> diff --git a/src/util/virhostcpu.c b/src/util/virhostcpu.c
> index bf7fda23af..7f577c3e3e 100644
> --- a/src/util/virhostcpu.c
> +++ b/src/util/virhostcpu.c
> @@ -1535,3 +1535,42 @@ virHostCPUGetSignature(char **signature)
>  }
>  
>  #endif /* __linux__ */
> +
> +int
> +virHostCPUGetHaltPollTime(pid_t pid,
> +                      unsigned long long *haltPollSuccess,
> +                      unsigned long long *haltPollFail)
> +{
> +    g_autofree char *pidToStr = NULL;
> +    g_autofree char *debugFsPath = NULL;
> +    g_autofree char *kvmPath = NULL;
> +    struct dirent *ent = NULL;
> +    g_autoptr(DIR) dir = NULL;
> +    bool found = false;
> +
> +    if (!(debugFsPath = virFileFindMountPoint("debugfs")))
> +        return -1;
> +
> +    kvmPath = g_strdup_printf("%s/%s", debugFsPath, "kvm");
> +    if (virDirOpenQuiet(&dir, kvmPath) != 1)
> +        return -1;
> +
> +    pidToStr = g_strdup_printf("%lld%c", (long long)pid, '-');

Just a tiny nit: this could be "%lld-".

> +    while (virDirRead(dir, &ent, NULL) > 0) {
> +        if (STRPREFIX(ent->d_name, pidToStr)) {
> +            found = true;
> +            break;
> +        }
> +    }
> +
> +    if (!found)
> +        return -1;
> +
> +    if (virFileReadValueUllongQuiet(haltPollSuccess, "%s/%s/%s", kvmPath,
> +                                    ent->d_name, "halt_poll_success_ns") < 0 ||
> +        virFileReadValueUllongQuiet(haltPollFail, "%s/%s/%s", kvmPath,
> +                                    ent->d_name, "halt_poll_fail_ns") < 0)
> +        return -1;
> +
> +    return 0;
> +}

Michal