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Umesh Nerlige Ramappa 431b742e2b drm/i915/pmu: Fix zero delta busyness issue 
When running igt@gem_exec_balancer@individual for multiple iterations,
it is seen that the delta busyness returned by PMU is 0. The issue stems
from a combination of 2 implementation specific details:

1) gt_park is throttling __update_guc_busyness_stats() so that it does
not hog PCI bandwidth for some use cases. (Ref: 59bcdb564b)

2) busyness implementation always returns monotonically increasing
counters. (Ref: cf907f6d29)

If an application queried an engine while it was active,
engine->stats.guc.running is set to true. Following that, if all PM
wakeref's are released, then gt is parked. At this time the throttling
of __update_guc_busyness_stats() may result in a missed update to the
running state of the engine (due to (1) above). This means subsequent
calls to guc_engine_busyness() will think that the engine is still
running and they will keep updating the cached counter (stats->total).
This results in an inflated cached counter.

Later when the application runs a workload and queries for busyness, we
return the cached value since it is larger than the actual value (due to
(2) above)

All subsequent queries will return the same large (inflated) value, so
the application sees a delta busyness of zero.

Fix the issue by resetting the running state of engines each time
intel_guc_busyness_park() is called.

v2: (Rodrigo)
- Use the correct tag in commit message
- Drop the redundant wakeref check in guc_engine_busyness() and update
  commit message

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13366
Fixes: cf907f6d29 ("i915/guc: Ensure busyness counter increases motonically")
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250123193839.2394694-1-umesh.nerlige.ramappa@intel.com
History 2025-01-27 13:06:17 -08:00
arch Linux 6.9-rc6 2024-04-29 20:22:39 +02:00
block vfs-6.9-rc6.fixes 2024-04-26 11:01:28 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression that broke iwd as well as a divide by 2024-03-25 10:48:23 -07:00
Documentation drm/i915/hwmon: expose fan speed 2024-08-28 12:06:07 +05:30
drivers drm/i915/pmu: Fix zero delta busyness issue 2025-01-27 13:06:17 -08:00
fs three smb3 client fixes, all also for stable 2024-04-27 11:35:40 -07:00
include drm/i915: Support replaying GPU hangs with captured context image 2024-05-16 07:37:05 +00:00
init Rust fixes for v6.9 2024-04-27 12:11:55 -07:00
io_uring io_uring/net: restore msg_control on sendzc retry 2024-04-08 21:48:41 -06:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel Misc fixes: 2024-04-28 12:11:26 -07:00
lib 11 hotfixes. 8 are cc:stable and the remaining 3 (nice ratio!) address 2024-04-26 13:48:03 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio() 2024-04-25 10:07:27 -07:00
net Including fixes from netfilter, wireless and bluetooth. 2024-04-25 11:19:38 -07:00
rust rust: remove params from module macro example 2024-04-25 17:34:33 +02:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts Rust fixes for v6.9 2024-04-27 12:11:55 -07:00
security security: Place security_path_post_mknod() where the original IMA call was 2024-04-03 10:21:32 -07:00
sound ALSA: seq: ump: Fix conversion from MIDI2 to MIDI1 UMP messages 2024-04-19 12:07:14 +02:00
tools RISC-V Fixes for 6.9-rc6 2024-04-27 12:02:55 -07:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start() 2024-04-11 12:58:53 -07:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap Including fixes from netfilter, wireless and bluetooth. 2024-04-25 11:19:38 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge tag 'drm-msm-next-2024-05-07' of https://gitlab.freedesktop.org/drm/msm into drm-next 2024-05-10 10:22:59 +10:00
Makefile Linux 6.9-rc6 2024-04-28 13:47:24 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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 reStructuredText 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.