On 2021/7/19 17:05, Peter Krempa wrote:
> On Fri, Jul 16, 2021 at 18:42:22 +0800, Yang Fei wrote:
>> Add helper function virGetCpuHaltPollTime 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@xxxxxxxxxx>
>> ---
>> src/libvirt_private.syms | 1 +
>> src/util/virutil.c | 43 ++++++++++++++++++++++++++++++++++++++++
>> src/util/virutil.h | 4 ++++
>> 3 files changed, 48 insertions(+)
>>
>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>> index 68e4b6aab8..64aff4eca4 100644
>> --- a/src/libvirt_private.syms
>> +++ b/src/libvirt_private.syms
>> @@ -3479,6 +3479,7 @@ virDoesUserExist;
>> virDoubleToStr;
>> virFormatIntDecimal;
>> virFormatIntPretty;
>> +virGetCpuHaltPollTime;
>> virGetDeviceID;
>> virGetDeviceUnprivSGIO;
>> virGetGroupID;
>> diff --git a/src/util/virutil.c b/src/util/virutil.c
>> index 311cbbf93a..f5304644c0 100644
>> --- a/src/util/virutil.c
>> +++ b/src/util/virutil.c
>> @@ -1936,3 +1936,46 @@ virPipeNonBlock(int fds[2])
>> {
>> return virPipeImpl(fds, true, true);
>> }
>> +
>> +int
>> +virGetCpuHaltPollTime(pid_t pid,
>> + unsigned long long *haltPollSuccess,
>> + unsigned long long *haltPollFail)
>> +{
>> + g_autofree char *pidToStr = NULL;
>> + g_autofree char *debugFsPath = NULL;
>> + g_autofree char *completePath = NULL;
>> + struct dirent *ent = NULL;
>> + g_autoptr(DIR) dir = NULL;
>> + int ret = -1;
>> + bool found = false;
>> +
>> + if (!(debugFsPath = virFileFindMountPoint("debugfs")))
>> + return ret;
>
> Here '-1' is returned, but no libvirt error is reported ...
>
>> +
>> + completePath = g_strdup_printf("%s/%s", debugFsPath, "kvm");
>> + if (virDirOpenIfExists(&dir, completePath) != 1)
>> + return ret;
>
> While here -1 is reported and an error may be reported (e.g on EACCESS).
> We generally avoid this pattern because the caller cant properly handle
> that.
>
>> +
>> + pidToStr = g_strdup_printf("%d%c", pid, '-');
>
> I'm fairly certain this will fail to compile on mingw since %d isn't the
> proper formatting modifier for pid_t.
>
In the last version, I try to use %lld but failed in the ninja test.
How about forcibly converts the variable pid to long long?
Like this:
g_strdup_printf("%lld%c", (long long)pid, '-')
I find that this is used elsewhere in the code.
>> + while (virDirRead(dir, &ent, NULL) > 0) {
>> + if (STRPREFIX(ent->d_name, pidToStr)) {
>
> Any idea what the suffix after '-' in the debugfs entry is? If we can
> figure it out we won't have to look up the correct file.
>
The full directory name format is "pid-fd", The fd is assigned during VM creation.
As I know, we can find it in /proc/(qemu-kvm pid)/fd, but also need to look up which
one points to "anon_inode:kvm-vm". That may not be any more efficient than look up
it in the kvm directory.
>> + found = true;
>> + break;
>> + }
>> + }
>> +
>> + if (!found)
>> + return ret;
>> +
>> + if (virFileReadValueUllong(haltPollSuccess, "%s/%s/%s", completePath,
>> + ent->d_name, "halt_poll_success_ns") < 0
>> + || virFileReadValueUllong(haltPollFail, "%s/%s/%s", completePath,
>> + ent->d_name, "halt_poll_fail_ns") < 0) {
>
> As you can see here, this is one of the functions having terrible
> semantics. It sometimes does set the libvirt error object and sometimes
> doesn't, thats why we try to avoid those.
>
>> + return ret;
>> + }
>> +
>> + ret = 0;
>> +
>> + return ret;
>> +}
>
> .
>
Thanks,
Fei.
