mirror of
https://github.com/torvalds/linux.git
synced 2026-08-01 12:11:59 +02:00
Linux kernel source tree
5979873ebb
Irrespective of the backend for request submissions, busyness for an engine with an active context is calculated using: busyness = total + (current_time - context_switch_in_time) In execlists mode of operation, the context switch events are handled by the CPU. Context switch in/out time and current_time are captured in CPU time domain using ktime_get(). In GuC mode of submission, context switch events are handled by GuC and the times in the above formula are captured in GT clock domain. This information is shared with the CPU through shared memory. This results in 2 caveats: 1) The time taken between start of a batch and the time that CPU is able to see the context_switch_in_time in shared memory is dependent on GuC and memory bandwidth constraints. 2) Determining current_time requires an MMIO read that can take anywhere between a few us to a couple ms. A reference CPU time is captured soon after reading the MMIO so that the caller can compare the cpu delta between 2 busyness samples. The issue here is that the CPU delta and the busyness delta can be skewed because of the time taken to read the register. These 2 factors affect the accuracy of the selftest - live_engine_busy_stats. For (1) the selftest waits until busyness stats are visible to the CPU. The effects of (2) are more prominent for the current busyness sample period of 100 us. Increase the busyness sample period from 100 us to 10 ms to overccome (2). v2: Fix checkpatch issues Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com> Reviewed-by: Matthew Brost <matthew.brost@intel.com> Signed-off-by: John Harrison <John.C.Harrison@Intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20211115221640.30793-1-umesh.nerlige.ramappa@intel.com |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.
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.