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Umesh Nerlige Ramappa cb5fab2afd
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
(cherry picked from commit 431b742e2bfc9f6dd713f261629741980996d001)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
2025-02-03 09:26:42 -05:00
arch sh updates for v6.14 2025-02-02 10:40:27 -08:00
block block-6.14-20250131 2025-01-31 11:49:30 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
Documentation 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
drivers drm/i915/pmu: Fix zero delta busyness issue 2025-02-03 09:26:42 -05:00
fs assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
include assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
init Kbuild updates for v6.14 2025-01-31 12:07:07 -08:00
io_uring io_uring-6.14-20250131 2025-01-31 11:29:23 -08:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
lib 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
net assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
rust Kbuild updates for v6.14 2025-01-31 12:07:07 -08:00
samples AT_EXECVE_CHECK update for v6.14-rc1 (fix1) 2025-01-31 17:12:31 -08:00
scripts 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
security treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
sound sound fixes for 6.14-rc1 2025-01-31 09:17:02 -08:00
tools Turbostat 2025.02.02 updates since 2024.11.30 2025-02-02 10:49:13 -08:00
usr kbuild: Drop support for include/asm-<arch> in headers_check.pl 2024-12-21 11:43:17 +09:00
virt Merge branch 'kvm-mirror-page-tables' into HEAD 2025-01-20 07:15:58 -05:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-01-10 00:17:25 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: use host dylib naming convention to support macOS 2025-01-10 01:01:24 +01:00
.mailmap 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
.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 Mainly individually changelogged singleton patches. The patch series in 2025-01-26 17:50:53 -08:00
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 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
Makefile Linux 6.14-rc1 2025-02-02 15:39:26 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.