lkml.org 
[lkml]   [2022]   [May]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[PATCH v2 0/2] locking/atomic/x86: Introduce arch_try_cmpxchg64
Date
The followign patchset introduces generic support for try_cmpxchg64
and introduces arch_try_cmpxchg64 for 64-bit and 32-bit targets.
On 64-bit targets, the generated assembly improves from:

ab: 89 c8 mov %ecx,%eax
ad: 48 89 4c 24 60 mov %rcx,0x60(%rsp)
b2: 83 e0 fd and $0xfffffffd,%eax
b5: 89 54 24 64 mov %edx,0x64(%rsp)
b9: 88 44 24 60 mov %al,0x60(%rsp)
bd: 48 89 c8 mov %rcx,%rax
c0: c6 44 24 62 f2 movb $0xf2,0x62(%rsp)
c5: 48 8b 74 24 60 mov 0x60(%rsp),%rsi
ca: f0 49 0f b1 34 24 lock cmpxchg %rsi,(%r12)
d0: 48 39 c1 cmp %rax,%rcx
d3: 75 cf jne a4 <t+0xa4>

to:

b3: 89 c2 mov %eax,%edx
b5: 48 89 44 24 60 mov %rax,0x60(%rsp)
ba: 83 e2 fd and $0xfffffffd,%edx
bd: 89 4c 24 64 mov %ecx,0x64(%rsp)
c1: 88 54 24 60 mov %dl,0x60(%rsp)
c5: c6 44 24 62 f2 movb $0xf2,0x62(%rsp)
ca: 48 8b 54 24 60 mov 0x60(%rsp),%rdx
cf: f0 48 0f b1 13 lock cmpxchg %rdx,(%rbx)
d4: 75 d5 jne ab <t+0xab>

where a move and a compare after cmpxchg is saved. The improvements
for 32-bit targets are even more noticeable, because dual-word compare
after cmpxchg8b gets eliminated.

Changes since v1:
* Implement full support for try_cmpxchg64{,_acquire,_release,_relaxed}
and their falbacks involving cmpxchg64.
* Split patch to generic and target-dependant part.
* Modernize __try_cmpxchg64 asm template with symbolic operand name.
* Use generic fallback when arch_try_cmpxchg64 is not defined.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Marco Elver <elver@google.com>

Uros Bizjak (2):
locking/atomic: Add generic try_cmpxchg64 support
locking/atomic/x86: Introduce arch_try_cmpxchg64

arch/x86/include/asm/cmpxchg_32.h | 21 ++++++
arch/x86/include/asm/cmpxchg_64.h | 6 ++
include/linux/atomic/atomic-arch-fallback.h | 72 ++++++++++++++++++++-
include/linux/atomic/atomic-instrumented.h | 40 +++++++++++-
scripts/atomic/gen-atomic-fallback.sh | 31 +++++----
scripts/atomic/gen-atomic-instrumented.sh | 2 +-
6 files changed, 156 insertions(+), 16 deletions(-)

--
2.35.1

\
 
 \ /
  Last update: 2022-05-13 17:31    [W:0.131 / U:1.428 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site