There are a number of free running counters introduced for uncore, which
provide highly valuable information to a wide array of customers.
For example, Skylake Server has IIO free running counters to collect
Input/Output x BW/Utilization.
There is NO event available on the general purpose counters, that is
exactly the same as the free running counters. The generic uncore code
needs to be enhanced to support the new counters.
In the uncore document, there is no event-code assigned to free running
counters. Some events need to be defined to indicate the free running
counters. The events are encoded as event-code + umask-code.
The event-code for all free running counters is 0xff, which is the same
as the fixed counters:
- It has not been decided what code will be used for common events on
future platforms. 0xff is the only one which will definitely not be
used as any common event-code.
- Cannot re-use current events on the general purpose counters. Because
there is NO event available, that is exactly the same as the free
running counters.
- Even in the existing codes, the fixed counters for core, that have the
same event-code, may count different things. Hence, it should not
surprise the users if the free running counters that share the same
event-code also count different things.
Umask will be used to distinguish the counters.
The umask-code is used to distinguish a fixed counter and a free running
counter, and different types of free running counters.
For fixed counters, the umask-code is 0x0X, where X indicates the index
of the fixed counter, which starts from 0.
- Compatible with the old event encoding.
- Currently, there is only one fixed counter. There are still 15
reserved spaces for extension.
For free running counters, the umask-code uses the rest of the space.
It would follow the format of 0xXY:
- X stands for the type of free running counters, which starts from 1.
- Y stands for the index of free running counters of same type, which
starts from 0.
- The free running counters do different thing. It can be categorized to
several types, according to the MSR location, bit width and
definition. E.g. there are three types of IIO free running counters on
Skylake server to monitor IO CLOCKS, BANDWIDTH and UTILIZATION on
different ports. It makes it easy to locate the free running counter
of a specific type.
- So far, there are at most 8 counters of each type. There are still 8
reserved spaces for extension.
Introducing a new index to indicate the free running counters. Only one
index is enough for all free running counters. Because the free running
counters are always active, and the event and free running counter are
always 1:1 mapped, it does not need extra index to indicate the assigned
counter.
Introducing a new data structure to store free running counters related
information for each type. It includes the number of counters, bit
width, base address, offset between counters and offset between boxes.
Introducing several inline helpers to check index for fixed counter and
free running counter, validate free running counter event, and retrieve
the free running counter information according to box and event.
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: acme@kernel.org
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1525371913-10597-4-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
927b2deb06