[libvirt] [PATCH 1/5] util, resctrl: using 64bit interface instead of 32bit for counters

[Wang Huaqiang]

On 2019/12/16 下午6:12, Daniel P. Berrangé wrote:
> On Sun, Dec 15, 2019 at 02:39:20AM +0000, Wang, Huaqiang wrote:
>> Hi Daniel,
>>
>> Thanks for your review.
>>
>> About patch 1/5, I understand we should be very cautious when we changes  the determined
>> interface.
>>
>> I'd like to reserved the old 32bit interface  and propose a new 64bit interface just as you
>> suggested if you still think so after you  got my intention.
>> Here actually I want to fix a bug, maybe I should title this patch as *bug fixing*. Reason is the
>> underlying hardware, the cache monitor and memory bandwidth counters, are 64bit width.
>> Using 32bit interface to access these counters are problematic. This bug is not found because
>> this interface is only used for tracking the amount of cache that used before this patch, normally
>> the occupied cache will not exceed 4GB range. (32bit counter can counter value up to 4GB).
>> But for memory, this counter records the data passing through the memory controller issued
>> by this CPU in bytes and accumulatively, this value can easily exceed the 4GB bound, so I
>> don’t want to reserve the old 32 bit interface and let user use it, because it will report incorrect value.
> We simply have to document the limitati onof the old interface. We can
> *NOT* change it, because it WILL break API compatibility for apps that
> deserailize the current data.


Got. I'll resend new patches for review.


Thanks

Huaqiang


>
>
> Regards,
> Daniel