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Rafael J. Wysocki 19f4e86b2c Revert "cpuidle: menu: Avoid discarding useful information" 
commit 10fad40122 upstream.

It is reported that commit 85975daeaa ("cpuidle: menu: Avoid discarding
useful information") led to a performance regression on Intel Jasper Lake
systems because it reduced the time spent by CPUs in idle state C7 which
is correlated to the maximum frequency the CPUs can get to because of an
average running power limit [1].

Before that commit, get_typical_interval() would have returned UINT_MAX
whenever it had been unable to make a high-confidence prediction which
had led to selecting the deepest available idle state too often and
both power and performance had been inadequate as a result of that on
some systems.  However, this had not been a problem on systems with
relatively aggressive average running power limits, like the Jasper Lake
systems in question, because on those systems it was compensated by the
ability to run CPUs faster.

It was addressed by causing get_typical_interval() to return a number
based on the recent idle duration information available to it even if it
could not make a high-confidence prediction, but that clearly did not
take the possible correlation between idle power and available CPU
capacity into account.

For this reason, revert most of the changes made by commit 85975daeaa,
except for one cosmetic cleanup, and add a comment explaining the
rationale for returning UINT_MAX from get_typical_interval() when it
is unable to make a high-confidence prediction.

Fixes: 85975daeaa ("cpuidle: menu: Avoid discarding useful information")
Closes: https://lore.kernel.org/linux-pm/36iykr223vmcfsoysexug6s274nq2oimcu55ybn6ww4il3g3cv@cohflgdbpnq7/ [1]
Reported-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/3663603.iIbC2pHGDl@rafael.j.wysocki
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-10-29 14:08:56 +01:00
arch arm64, mm: avoid always making PTE dirty in pte_mkwrite() 2025-10-29 14:08:55 +01:00
block blk-crypto: fix missing blktrace bio split events 2025-10-19 16:33:48 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:33:42 +02:00
Documentation arm64: errata: Apply workarounds for Neoverse-V3AE 2025-10-23 16:20:47 +02:00
drivers Revert "cpuidle: menu: Avoid discarding useful information" 2025-10-29 14:08:56 +01:00
fs xfs: fix locking in xchk_nlinks_collect_dir 2025-10-29 14:08:56 +01:00
include mm/ksm: fix flag-dropping behavior in ksm_madvise 2025-10-23 16:20:47 +02:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring Revert "io_uring/rw: drop -EOPNOTSUPP check in __io_complete_rw_common()" 2025-10-23 16:20:26 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel dma-debug: don't report false positives with DMA_BOUNCE_UNALIGNED_KMALLOC 2025-10-29 14:08:55 +01:00
lib lib/crypto/curve25519-hacl64: Disable KASAN with clang-17 and older 2025-10-19 16:34:00 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm slab: reset slab->obj_ext when freeing and it is OBJEXTS_ALLOC_FAIL 2025-10-23 16:20:18 +02:00
net sctp: avoid NULL dereference when chunk data buffer is missing 2025-10-29 14:08:55 +01:00
rust mm/ksm: fix flag-dropping behavior in ksm_madvise 2025-10-23 16:20:47 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-06 11:17:52 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:33:51 +02:00
sound ASoC: amd/sdw_utils: avoid NULL deref when devm_kasprintf() fails 2025-10-23 16:20:37 +02:00
tools selftests: net: fix server bind failure in sctp_vrf.sh 2025-10-29 14:08:54 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.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 2025-08-01 09:48:44 +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 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 rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -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 MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -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 MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Unbreak 'make tools/*' for user-space targets 2025-10-29 14:08:53 +01:00
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.