[PATCH 3/3] domaincapsmoc.c: mock virHostCPUGetMicrocodeVersion()

[Daniel Henrique Barboza]

On 8/24/20 11:36 AM, Ján Tomko wrote:
> s/capsmoc.c/capsmock/
> 
> On a Monday in 2020, Daniel Henrique Barboza wrote:
>> Previous patch handled the runtime case where a non-x86 host is
>> fetching /proc/cpuinfo data for a microcode info that we know
>> it doesn't exist. This change alone speeded everything by a
>> bit for non-x86, but there is at least one major culprit left.
>>
>> qemuxml2argvtest does several arch-specific tests, and a good
>> chunk of them are x86 exclusive. This means that 'hostArch'
>> will be seen as x86 for these tests, even when running in
>> non-x86 hosts. In a Power 9 server with 128 CPUs, qemuxmlargvtest
> 
> *qemuxml2argvtest
> 
>> takes 298 seconds to complete in average, and 'perf record'
>> indicates that 95% of the time is spent in
>> virHostCPUGetMicrocodeVersion().
>>
> 
> No surprise, we call it 23448 times.
> 
>> This patch mocks virHostCPUGetMicrocodeVersion() to always return
>> 0 in the tests, avoiding /proc/cpuinfo reads. This will make all
>> tests behave arch-agnostic, and the microcode value being 0 has no
>> impact on any existing test.
>>
>> This is a CI speed across the board for all archs, including x86,
>> given that we're not reading /proc/cpuinfo in the tests. For
>> a Thinkpad T480 laptop with 8 Intel i7 CPUs, qemuxml2argvtest
>> went from 15.50 sec to 12.50 seconds. The performance gain is even
>> more noticeable for huge servers with lots of CPUs. For the
>> Power 9 server mentioned above, this patch speeds qemuxml2argvtest
>> to 9 seconds, down from 298 sec.
>>
> 
> I assume the speedup for Power is measured for the whole series, not
> just for this patch.


Yes, for the whole series, for both Power and my x86 laptop. Should've make
it clearer in the commit msg.


Thanks,


DHB


> 
>> Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>
>> ---
>> src/util/virhostcpu.h  | 3 ++-
>> tests/domaincapsmock.c | 6 ++++++
>> 2 files changed, 8 insertions(+), 1 deletion(-)
>>
> 
> Reviewed-by: Ján Tomko <jtomko at redhat.com>
> 
> Jano