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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> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.