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Code that passes a 32-bit constant into cmpxchg() produces a harmless
sparse warning because of the truncation in the branch that is not taken:
fs/erofs/zdata.c: note: in included file (through /home/arnd/arm-soc/arch/arm/include/asm/cmpxchg.h, /home/arnd/arm-soc/arch/arm/include/asm/atomic.h, /home/arnd/arm-soc/include/linux/atomic.h, ...):
include/asm-generic/cmpxchg-local.h:29:33: warning: cast truncates bits from constant value (5f0ecafe becomes fe)
include/asm-generic/cmpxchg-local.h:33:34: warning: cast truncates bits from constant value (5f0ecafe becomes cafe)
include/asm-generic/cmpxchg-local.h:29:33: warning: cast truncates bits from constant value (5f0ecafe becomes fe)
include/asm-generic/cmpxchg-local.h:30:42: warning: cast truncates bits from constant value (5f0edead becomes ad)
include/asm-generic/cmpxchg-local.h:33:34: warning: cast truncates bits from constant value (5f0ecafe becomes cafe)
include/asm-generic/cmpxchg-local.h:34:44: warning: cast truncates bits from constant value (5f0edead becomes dead)
This was reported as a regression to Matt's recent __generic_cmpxchg_local
patch, though this patch only added more warnings on top of the ones
that were already there.
Rewording the truncation to use an explicit bitmask instead of a cast
to a smaller type avoids the warning but otherwise leaves the code
unchanged.
I had another look at why the cast is even needed for atomic_cmpxchg(),
and as Matt describes the problem here is that atomic_t contains a
signed 'int', but cmpxchg() takes an 'unsigned long' argument, and
converting between the two leads to a 64-bit sign-extension of
negative 32-bit atomics.
I checked the other implementations of arch_cmpxchg() and did not find
any others that run into the same problem as __generic_cmpxchg_local(),
but it's easy to be on the safe side here and always convert the
signed int into an unsigned int when calling arch_cmpxchg(), as this
will work even when any of the arch_cmpxchg() implementations run
into the same problem.
Fixes: 624654152284 ("locking/atomic: cmpxchg: Make __generic_cmpxchg_local compare against zero-extended 'old' value")
Reviewed-by: Matt Evans <mev@rivosinc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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zero-extended 'old' value
__generic_cmpxchg_local takes unsigned long old/new arguments which
might end up being up-cast from smaller signed types (which will
sign-extend). The loaded compare value must be compared against a
truncated smaller type, so down-cast appropriately for each size.
The issue is apparent on 64-bit machines with code, such as
atomic_dec_unless_positive(), that sign-extends from int.
64-bit machines generally don't use the generic cmpxchg but
development/early ports might make use of it, so make it correct.
Signed-off-by: Matt Evans <mev@rivosinc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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The asm-generic implementations of cmpxchg_local() and cmpxchg64_local()
use a `_generic` suffix to distinguish themselves from arch code or
wrappers used elsewhere.
Subsequent patches will add ARCH_ATOMIC support to these
implementations, and will distinguish more functions with a `generic`
portion. To align with how ARCH_ATOMIC uses an `arch_` prefix, it would
be helpful to use a `generic_` prefix rather than a `_generic` suffix.
In preparation for this, this patch renames the existing functions to
make `generic` a prefix rather than a suffix. There should be no
functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210525140232.53872-12-mark.rutland@arm.com
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Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Fix uninitialized return code in default case in cmpxchg-local.h
This patch fixes the code to prevent an uninitialized return value that is detected
when compiling with clang. The bug produces numerous warnings when compiling the
Linux kernel with clang.
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
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The interrupt disabled region is extremly tiny and therefor not
latency relevant. Avoid cluttering the traces with those pointless
entries.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Fix the IRQ flag handling naming. In linux/irqflags.h under one configuration,
it maps:
local_irq_enable() -> raw_local_irq_enable()
local_irq_disable() -> raw_local_irq_disable()
local_irq_save() -> raw_local_irq_save()
...
and under the other configuration, it maps:
raw_local_irq_enable() -> local_irq_enable()
raw_local_irq_disable() -> local_irq_disable()
raw_local_irq_save() -> local_irq_save()
...
This is quite confusing. There should be one set of names expected of the
arch, and this should be wrapped to give another set of names that are expected
by users of this facility.
Change this to have the arch provide:
flags = arch_local_save_flags()
flags = arch_local_irq_save()
arch_local_irq_restore(flags)
arch_local_irq_disable()
arch_local_irq_enable()
arch_irqs_disabled_flags(flags)
arch_irqs_disabled()
arch_safe_halt()
Then linux/irqflags.h wraps these to provide:
raw_local_save_flags(flags)
raw_local_irq_save(flags)
raw_local_irq_restore(flags)
raw_local_irq_disable()
raw_local_irq_enable()
raw_irqs_disabled_flags(flags)
raw_irqs_disabled()
raw_safe_halt()
with type checking on the flags 'arguments', and then wraps those to provide:
local_save_flags(flags)
local_irq_save(flags)
local_irq_restore(flags)
local_irq_disable()
local_irq_enable()
irqs_disabled_flags(flags)
irqs_disabled()
safe_halt()
with tracing included if enabled.
The arch functions can now all be inline functions rather than some of them
having to be macros.
Signed-off-by: David Howells <dhowells@redhat.com> [X86, FRV, MN10300]
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> [Tile]
Signed-off-by: Michal Simek <monstr@monstr.eu> [Microblaze]
Tested-by: Catalin Marinas <catalin.marinas@arm.com> [ARM]
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> [AVR]
Acked-by: Tony Luck <tony.luck@intel.com> [IA-64]
Acked-by: Hirokazu Takata <takata@linux-m32r.org> [M32R]
Acked-by: Greg Ungerer <gerg@uclinux.org> [M68K/M68KNOMMU]
Acked-by: Ralf Baechle <ralf@linux-mips.org> [MIPS]
Acked-by: Kyle McMartin <kyle@mcmartin.ca> [PA-RISC]
Acked-by: Paul Mackerras <paulus@samba.org> [PowerPC]
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> [S390]
Acked-by: Chen Liqin <liqin.chen@sunplusct.com> [Score]
Acked-by: Matt Fleming <matt@console-pimps.org> [SH]
Acked-by: David S. Miller <davem@davemloft.net> [Sparc]
Acked-by: Chris Zankel <chris@zankel.net> [Xtensa]
Reviewed-by: Richard Henderson <rth@twiddle.net> [Alpha]
Reviewed-by: Yoshinori Sato <ysato@users.sourceforge.jp> [H8300]
Cc: starvik@axis.com [CRIS]
Cc: jesper.nilsson@axis.com [CRIS]
Cc: linux-cris-kernel@axis.com
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Emulates the cmpxchg_local by disabling interrupts around variable modification.
This is not reentrant wrt NMIs and MCEs. It is only protected against normal
interrupts, but this is enough for architectures without such interrupt sources
or if used in a context where the data is not shared with such handlers.
It can be used as a fallback for architectures lacking a real cmpxchg
instruction.
For architectures that have a real cmpxchg but does not have NMIs or MCE,
testing which of the generic vs architecture specific cmpxchg is the fastest
should be done.
asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to
be used as a cmpxchg fallback for architectures that do not support SMP.
* Patch series comments
Using cmpxchg_local shows a performance improvements of the fast path goes from
a 66% speedup on a Pentium 4 to a 14% speedup on AMD64.
In detail:
Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Measurements on a Pentium4, 3GHz, Hyperthread.
SLUB Performance testing
========================
1. Kmalloc: Repeatedly allocate then free test
* slub HEAD, test 1
kmalloc(8) = 201 cycles kfree = 351 cycles
kmalloc(16) = 198 cycles kfree = 359 cycles
kmalloc(32) = 200 cycles kfree = 381 cycles
kmalloc(64) = 224 cycles kfree = 394 cycles
kmalloc(128) = 285 cycles kfree = 424 cycles
kmalloc(256) = 411 cycles kfree = 546 cycles
kmalloc(512) = 480 cycles kfree = 619 cycles
kmalloc(1024) = 623 cycles kfree = 750 cycles
kmalloc(2048) = 686 cycles kfree = 811 cycles
kmalloc(4096) = 482 cycles kfree = 538 cycles
kmalloc(8192) = 680 cycles kfree = 734 cycles
kmalloc(16384) = 713 cycles kfree = 843 cycles
* Slub HEAD, test 2
kmalloc(8) = 190 cycles kfree = 351 cycles
kmalloc(16) = 195 cycles kfree = 360 cycles
kmalloc(32) = 201 cycles kfree = 370 cycles
kmalloc(64) = 245 cycles kfree = 389 cycles
kmalloc(128) = 283 cycles kfree = 413 cycles
kmalloc(256) = 409 cycles kfree = 547 cycles
kmalloc(512) = 476 cycles kfree = 616 cycles
kmalloc(1024) = 628 cycles kfree = 753 cycles
kmalloc(2048) = 684 cycles kfree = 811 cycles
kmalloc(4096) = 480 cycles kfree = 539 cycles
kmalloc(8192) = 661 cycles kfree = 746 cycles
kmalloc(16384) = 741 cycles kfree = 856 cycles
* cmpxchg_local Slub test
kmalloc(8) = 83 cycles kfree = 363 cycles
kmalloc(16) = 85 cycles kfree = 372 cycles
kmalloc(32) = 92 cycles kfree = 377 cycles
kmalloc(64) = 115 cycles kfree = 397 cycles
kmalloc(128) = 179 cycles kfree = 438 cycles
kmalloc(256) = 314 cycles kfree = 564 cycles
kmalloc(512) = 398 cycles kfree = 615 cycles
kmalloc(1024) = 573 cycles kfree = 745 cycles
kmalloc(2048) = 629 cycles kfree = 816 cycles
kmalloc(4096) = 473 cycles kfree = 548 cycles
kmalloc(8192) = 659 cycles kfree = 745 cycles
kmalloc(16384) = 724 cycles kfree = 843 cycles
2. Kmalloc: alloc/free test
* slub HEAD, test 1
kmalloc(8)/kfree = 322 cycles
kmalloc(16)/kfree = 318 cycles
kmalloc(32)/kfree = 318 cycles
kmalloc(64)/kfree = 325 cycles
kmalloc(128)/kfree = 318 cycles
kmalloc(256)/kfree = 328 cycles
kmalloc(512)/kfree = 328 cycles
kmalloc(1024)/kfree = 328 cycles
kmalloc(2048)/kfree = 328 cycles
kmalloc(4096)/kfree = 678 cycles
kmalloc(8192)/kfree = 1013 cycles
kmalloc(16384)/kfree = 1157 cycles
* Slub HEAD, test 2
kmalloc(8)/kfree = 323 cycles
kmalloc(16)/kfree = 318 cycles
kmalloc(32)/kfree = 318 cycles
kmalloc(64)/kfree = 318 cycles
kmalloc(128)/kfree = 318 cycles
kmalloc(256)/kfree = 328 cycles
kmalloc(512)/kfree = 328 cycles
kmalloc(1024)/kfree = 328 cycles
kmalloc(2048)/kfree = 328 cycles
kmalloc(4096)/kfree = 648 cycles
kmalloc(8192)/kfree = 1009 cycles
kmalloc(16384)/kfree = 1105 cycles
* cmpxchg_local Slub test
kmalloc(8)/kfree = 112 cycles
kmalloc(16)/kfree = 103 cycles
kmalloc(32)/kfree = 103 cycles
kmalloc(64)/kfree = 103 cycles
kmalloc(128)/kfree = 112 cycles
kmalloc(256)/kfree = 111 cycles
kmalloc(512)/kfree = 111 cycles
kmalloc(1024)/kfree = 111 cycles
kmalloc(2048)/kfree = 121 cycles
kmalloc(4096)/kfree = 650 cycles
kmalloc(8192)/kfree = 1042 cycles
kmalloc(16384)/kfree = 1149 cycles
Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Measurements on a AMD64 2.0 GHz dual-core
In this test, we seem to remove 10 cycles from the kmalloc fast path.
On small allocations, it gives a 14% performance increase. kfree fast
path also seems to have a 10 cycles improvement.
1. Kmalloc: Repeatedly allocate then free test
* cmpxchg_local slub
kmalloc(8) = 63 cycles kfree = 126 cycles
kmalloc(16) = 66 cycles kfree = 129 cycles
kmalloc(32) = 76 cycles kfree = 138 cycles
kmalloc(64) = 100 cycles kfree = 288 cycles
kmalloc(128) = 128 cycles kfree = 309 cycles
kmalloc(256) = 170 cycles kfree = 315 cycles
kmalloc(512) = 221 cycles kfree = 357 cycles
kmalloc(1024) = 324 cycles kfree = 393 cycles
kmalloc(2048) = 354 cycles kfree = 440 cycles
kmalloc(4096) = 394 cycles kfree = 330 cycles
kmalloc(8192) = 523 cycles kfree = 481 cycles
kmalloc(16384) = 643 cycles kfree = 649 cycles
* Base
kmalloc(8) = 74 cycles kfree = 113 cycles
kmalloc(16) = 76 cycles kfree = 116 cycles
kmalloc(32) = 85 cycles kfree = 133 cycles
kmalloc(64) = 111 cycles kfree = 279 cycles
kmalloc(128) = 138 cycles kfree = 294 cycles
kmalloc(256) = 181 cycles kfree = 304 cycles
kmalloc(512) = 237 cycles kfree = 327 cycles
kmalloc(1024) = 340 cycles kfree = 379 cycles
kmalloc(2048) = 378 cycles kfree = 433 cycles
kmalloc(4096) = 399 cycles kfree = 329 cycles
kmalloc(8192) = 528 cycles kfree = 624 cycles
kmalloc(16384) = 651 cycles kfree = 737 cycles
2. Kmalloc: alloc/free test
* cmpxchg_local slub
kmalloc(8)/kfree = 96 cycles
kmalloc(16)/kfree = 97 cycles
kmalloc(32)/kfree = 97 cycles
kmalloc(64)/kfree = 97 cycles
kmalloc(128)/kfree = 97 cycles
kmalloc(256)/kfree = 105 cycles
kmalloc(512)/kfree = 108 cycles
kmalloc(1024)/kfree = 105 cycles
kmalloc(2048)/kfree = 107 cycles
kmalloc(4096)/kfree = 390 cycles
kmalloc(8192)/kfree = 626 cycles
kmalloc(16384)/kfree = 662 cycles
* Base
kmalloc(8)/kfree = 116 cycles
kmalloc(16)/kfree = 116 cycles
kmalloc(32)/kfree = 116 cycles
kmalloc(64)/kfree = 116 cycles
kmalloc(128)/kfree = 116 cycles
kmalloc(256)/kfree = 126 cycles
kmalloc(512)/kfree = 126 cycles
kmalloc(1024)/kfree = 126 cycles
kmalloc(2048)/kfree = 126 cycles
kmalloc(4096)/kfree = 384 cycles
kmalloc(8192)/kfree = 749 cycles
kmalloc(16384)/kfree = 786 cycles
Tested-by: Christoph Lameter <clameter@sgi.com>
I can confirm Mathieus' measurement now:
Athlon64:
regular NUMA/discontig
1. Kmalloc: Repeatedly allocate then free test
10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles
10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles
10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles
10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles
10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles
10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles
10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles
10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles
10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles
10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles
10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles
10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles
2. Kmalloc: alloc/free test
10000 times kmalloc(8)/kfree -> 124 cycles
10000 times kmalloc(16)/kfree -> 124 cycles
10000 times kmalloc(32)/kfree -> 124 cycles
10000 times kmalloc(64)/kfree -> 124 cycles
10000 times kmalloc(128)/kfree -> 124 cycles
10000 times kmalloc(256)/kfree -> 132 cycles
10000 times kmalloc(512)/kfree -> 132 cycles
10000 times kmalloc(1024)/kfree -> 132 cycles
10000 times kmalloc(2048)/kfree -> 132 cycles
10000 times kmalloc(4096)/kfree -> 319 cycles
10000 times kmalloc(8192)/kfree -> 486 cycles
10000 times kmalloc(16384)/kfree -> 539 cycles
cmpxchg_local NUMA/discontig
1. Kmalloc: Repeatedly allocate then free test
10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles
10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles
10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles
10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles
10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles
10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles
10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles
10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles
10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles
10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles
10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles
10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles
2. Kmalloc: alloc/free test
10000 times kmalloc(8)/kfree -> 81 cycles
10000 times kmalloc(16)/kfree -> 81 cycles
10000 times kmalloc(32)/kfree -> 81 cycles
10000 times kmalloc(64)/kfree -> 81 cycles
10000 times kmalloc(128)/kfree -> 81 cycles
10000 times kmalloc(256)/kfree -> 91 cycles
10000 times kmalloc(512)/kfree -> 90 cycles
10000 times kmalloc(1024)/kfree -> 91 cycles
10000 times kmalloc(2048)/kfree -> 90 cycles
10000 times kmalloc(4096)/kfree -> 318 cycles
10000 times kmalloc(8192)/kfree -> 483 cycles
10000 times kmalloc(16384)/kfree -> 536 cycles
Changelog:
- Ran though checkpatch.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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