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Bitops API is the very basic, and it's widely used by the kernel. But
corresponding files are not maintained.
Bitmaps actively use bit operations, and big share of bitops material
already moves through the bitmap branch.
I would like to take a closer look to bitops.
This patch creates a BITOPS API record in the MAINTAINERS, and adds
Rasmus as a reviewer, and myself as a maintainer of those files.
CC: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
The function claims to return the bitmap size, if Nth bit doesn't exist.
This rule is violated in inline case because the fns() that is used
there doesn't know anything about size of the bitmap.
So, relax this requirement to '>= size', and make the outline
implementation a bit cheaper.
All in-tree kernel users of find_nth_bit() are safe against that.
Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Closes: https://lore.kernel.org/all/Zi50cAgR8nZvgLa3@yury-ThinkPad/T/#m6da806a0525e74dcc91f35e5f20766ed4e853e8a
Signed-off-by: Yury Norov <yury.norov@gmail.com>
The test now is limited to be compiled as a module. There's no technical
reason for it. Now that the test bears some performance benchmarks, it
would be reasonable to run it at kernel load time, before userspace
starts, to reduce possible jitter.
Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
The current fns() repeatedly uses __ffs() to find the index of the
least significant bit and then clears the corresponding bit using
__clear_bit(). The method for clearing the least significant bit can be
optimized by using word &= word - 1 instead.
Typically, the execution time of one __ffs() plus one __clear_bit() is
longer than that of a bitwise AND operation and a subtraction. To
improve performance, the loop for clearing the least significant bit
has been replaced with word &= word - 1, followed by a single __ffs()
operation to obtain the answer. This change reduces the number of
__ffs() iterations from n to just one, enhancing overall performance.
This modification significantly accelerates the fns() function in the
test_bitops benchmark, improving its speed by approximately 7.6 times.
Additionally, it enhances the performance of find_nth_bit() in the
find_bit benchmark by approximately 26%.
Before:
test_bitops: fns: 58033164 ns
find_nth_bit: 4254313 ns, 16525 iterations
After:
test_bitops: fns: 7637268 ns
find_nth_bit: 3362863 ns, 16501 iterations
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Introduce a benchmark test for the fns(). It measures the total time
taken by fns() to process 10,000 test data generated using
get_random_bytes() for each n in the range [0, BITS_PER_LONG).
example:
test_bitops: fns: 7637268 ns
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Rasmus Villemoes <linux@rasmusvillemoes.dk>
CC: David Laight <David.Laight@aculab.com>
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Suggested-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
In some cases like performance benchmarking, we need to call a
function, but don't need to read the returned value. If compiler
recognizes the function as pure or const, it can remove the function
invocation, which is not what we want.
To prevent that, the common practice is assigning the return value to
a temporary static volatile variable. From compiler's point of view,
the variable is unused because never read back after been assigned.
To make sure the variable is always emitted, we provide a __used
attribute. This works with GCC, but clang still emits
Wunused-but-set-variable. To suppress that warning, we need to teach
clang to do that with the 'unused' attribute.
Nathan Chancellor explained that in details:
While having used and unused attributes together might look unusual,
reading the GCC attribute manual makes it seem like these attributes
fulfill similar yet different roles, __unused__ prevents any unused
warnings while __used__ forces the variable to be emitted. A strict
reading of that does not make it seem like __used__ implies disabling
unused warnings
The compiler documentation makes it clear what happens behind the 'used'
and 'unused' attributes, but the chosen names may confuse readers if
such combination catches an eye in a random code.
This patch adds __always_used macro, which combines both attributes
and comments on what happens for those interested in details.
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/oe-kbuild-all/202405030808.UsoMKFNP-lkp@intel.com/
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Optimize topology_span_sane() by removing duplicate comparisons.
Since topology_span_sane() is called inside of for_each_cpu(), each
previous CPU has already been compared against every other CPU. The
current CPU only needs to be compared against higher-numbered CPUs.
The total number of comparisons is reduced from N * (N - 1) to
N * (N - 1) / 2 on each non-NUMA scheduling domain level.
Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Add for_each_cpu_from() as a generic cpumask macro.
for_each_cpu_from() is the same as for_each_cpu(), except it starts at
@cpu instead of zero.
Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Pull SoC fixes from Arnd Bergmann:
"The device tree changes this time are all for NXP i.MX platforms,
addressing issues with clocks and regulators on i.MX7 and i.MX8.
The old OMAP2 based Nokia N8x0 tablet get a couple of code fixes for
regressions that came in.
The ARM SCMI and FF-A firmware interfaces get a couple of minor bug
fixes.
A regression fix for RISC-V cache management addresses a problem with
probe order on Sifive cores"
* tag 'soc-fixes-6.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (23 commits)
MAINTAINERS: Change Krzysztof Kozlowski's email address
arm64: dts: imx8qm-ss-dma: fix can lpcg indices
arm64: dts: imx8-ss-dma: fix can lpcg indices
arm64: dts: imx8-ss-dma: fix adc lpcg indices
arm64: dts: imx8-ss-dma: fix pwm lpcg indices
arm64: dts: imx8-ss-dma: fix spi lpcg indices
arm64: dts: imx8-ss-conn: fix usb lpcg indices
arm64: dts: imx8-ss-lsio: fix pwm lpcg indices
ARM: dts: imx7s-warp: Pass OV2680 link-frequencies
ARM: dts: imx7-mba7: Use 'no-mmc' property
arm64: dts: imx8-ss-conn: fix usdhc wrong lpcg clock order
arm64: dts: freescale: imx8mp-venice-gw73xx-2x: fix USB vbus regulator
arm64: dts: freescale: imx8mp-venice-gw72xx-2x: fix USB vbus regulator
cache: sifive_ccache: Partially convert to a platform driver
firmware: arm_scmi: Make raw debugfs entries non-seekable
firmware: arm_scmi: Fix wrong fastchannel initialization
firmware: arm_ffa: Fix the partition ID check in ffa_notification_info_get()
ARM: OMAP2+: fix USB regression on Nokia N8x0
mmc: omap: restore original power up/down steps
mmc: omap: fix deferred probe
...
Pull iommu fixes from Joerg Roedel:
- Intel VT-d Fixes:
- Allocate local memory for PRQ page
- Fix WARN_ON in iommu probe path
- Fix wrong use of pasid config
- AMD IOMMU Fixes:
- Lock inversion fix
- Log message severity fix
- Disable SNP when v2 page-tables are used
- Mediatek driver:
- Fix module autoloading
* tag 'iommu-fixes-v6.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu:
iommu/amd: Change log message severity
iommu/vt-d: Fix WARN_ON in iommu probe path
iommu/vt-d: Allocate local memory for page request queue
iommu/vt-d: Fix wrong use of pasid config
iommu: mtk: fix module autoloading
iommu/amd: Do not enable SNP when V2 page table is enabled
iommu/amd: Fix possible irq lock inversion dependency issue
Switch Krzysztof Kozlowski's to @kernel.org account.
Link: https://lore.kernel.org/r/20240329174823.74918-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Pull pci fixes from Bjorn Helgaas:
- Revert a quirk that prevented Secondary Bus Reset for LSI / Agere
FW643.
We thought the device was broken, but the reset does work correctly
on other platforms, and the reset avoids leaking data out of VMs
(Bjorn Helgaas)
- Update MAINTAINERS to reflect that Gustavo Pimentel is no longer
reachable (Manivannan Sadhasivam)
* tag 'pci-v6.9-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci:
Revert "PCI: Mark LSI FW643 to avoid bus reset"
MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer
Use consistent log severity (pr_warn) to log all messages in SNP
enable path.
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20240410101643.32309-1-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
RISC-V SoC driver fixes for v6.9-rc3
A fix for the ccache driver which no longer probed after the PLIC driver
was converted to a platform driver. The JH7100 SoC depends on this
driver to provide cache management ops that must be registered with an
arch_initcall, so the ccache driver is partly converted to a platform
driver, registering only the cache management ops with the initcall and
the debug/edac register provision features of the driver as a platform
driver.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
* tag 'riscv-soc-fixes-for-v6.9-rc3' of https://git.kernel.org/pub/scm/linux/kernel/git/conor/linux:
cache: sifive_ccache: Partially convert to a platform driver
Link: https://lore.kernel.org/r/20240406-botch-disband-efc69b8236be@spud
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Pull block fixes from Jens Axboe:
- MD pull request via Song:
- UAF fix (Yu)
- Avoid out-of-bounds shift in blk-iocost (Rik)
- Fix for q->blkg_list corruption (Ming)
- Relax virt boundary mask/size segment checking (Ming)
* tag 'block-6.9-20240412' of git://git.kernel.dk/linux:
block: fix that blk_time_get_ns() doesn't update time after schedule
block: allow device to have both virt_boundary_mask and max segment size
block: fix q->blkg_list corruption during disk rebind
blk-iocost: avoid out of bounds shift
raid1: fix use-after-free for original bio in raid1_write_request()
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