diff options
| author | Borislav Petkov <bp@suse.de> | 2017-02-09 01:34:49 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-03-07 08:28:00 +0100 |
| commit | f25d384755191690b1196776d319cb6a4e899f28 (patch) | |
| tree | 78c7e11abba30dd40a2e753d7c83d30dcafc1ce5 /arch/x86/lib | |
| parent | 2140a9942b84dd4bf559dd1215b8f43c36ece5b5 (diff) | |
x86/asm: Optimize clear_page()
Currently, we CALL clear_page() which then JMPs to the proper function
chosen by the alternatives.
What we should do instead is CALL the proper function directly. (This
was something Ingo suggested a while ago). So let's do that.
Measuring our favourite kernel build workload shows that there are no
significant changes in performance.
AMD
===
-- /tmp/before 2017-02-09 18:01:46.451961188 +0100
++ /tmp/after 2017-02-09 18:01:54.883961175 +0100
@@ -1,15 +1,15 @@
Performance counter stats for 'system wide' (5 runs):
- 1028960.373643 cpu-clock (msec) # 6.000 CPUs utilized ( +- 1.41% )
+ 1023086.018961 cpu-clock (msec) # 6.000 CPUs utilized ( +- 1.20% )
- 518,744 context-switches # 0.504 K/sec ( +- 1.04% )
+ 518,254 context-switches # 0.507 K/sec ( +- 1.01% )
- 38,112 cpu-migrations # 0.037 K/sec ( +- 1.95% )
+ 37,917 cpu-migrations # 0.037 K/sec ( +- 1.02% )
- 20,874,266 page-faults # 0.020 M/sec ( +- 0.07% )
+ 20,918,897 page-faults # 0.020 M/sec ( +- 0.18% )
- 2,043,646,230,667 cycles # 1.986 GHz ( +- 0.14% ) (66.67%)
+ 2,045,305,584,032 cycles # 1.999 GHz ( +- 0.16% ) (66.67%)
- 553,698,855,431 stalled-cycles-frontend # 27.09% frontend cycles idle ( +- 0.07% ) (66.67%)
+ 555,099,401,413 stalled-cycles-frontend # 27.14% frontend cycles idle ( +- 0.13% ) (66.67%)
- 621,544,286,390 stalled-cycles-backend # 30.41% backend cycles idle ( +- 0.39% ) (66.67%)
+ 621,371,430,254 stalled-cycles-backend # 30.38% backend cycles idle ( +- 0.32% ) (66.67%)
- 1,738,364,431,659 instructions # 0.85 insn per cycle
+ 1,739,895,771,901 instructions # 0.85 insn per cycle
- # 0.36 stalled cycles per insn ( +- 0.11% ) (66.67%)
+ # 0.36 stalled cycles per insn ( +- 0.13% ) (66.67%)
- 391,170,943,850 branches # 380.161 M/sec ( +- 0.13% ) (66.67%)
+ 391,398,551,757 branches # 382.567 M/sec ( +- 0.13% ) (66.67%)
- 22,567,810,411 branch-misses # 5.77% of all branches ( +- 0.11% ) (66.67%)
+ 22,574,726,683 branch-misses # 5.77% of all branches ( +- 0.13% ) (66.67%)
- 171.480741921 seconds time elapsed ( +- 1.41% )
+ 170.509229451 seconds time elapsed ( +- 1.20% )
Intel
=====
-- /tmp/before 2017-02-09 20:36:19.851947473 +0100
++ /tmp/after 2017-02-09 20:36:30.151947458 +0100
@@ -1,15 +1,15 @@
Performance counter stats for 'system wide' (5 runs):
- 2207248.598126 cpu-clock (msec) # 8.000 CPUs utilized ( +- 0.69% )
+ 2213300.106631 cpu-clock (msec) # 8.000 CPUs utilized ( +- 0.73% )
- 899,342 context-switches # 0.407 K/sec ( +- 0.68% )
+ 898,381 context-switches # 0.406 K/sec ( +- 0.79% )
- 80,553 cpu-migrations # 0.036 K/sec ( +- 1.13% )
+ 80,979 cpu-migrations # 0.037 K/sec ( +- 1.11% )
- 36,171,148 page-faults # 0.016 M/sec ( +- 0.02% )
+ 36,179,791 page-faults # 0.016 M/sec ( +- 0.02% )
- 6,665,288,826,484 cycles # 3.020 GHz ( +- 0.07% ) (83.33%)
+ 6,671,638,410,799 cycles # 3.014 GHz ( +- 0.06% ) (83.33%)
- 5,065,975,115,197 stalled-cycles-frontend # 76.01% frontend cycles idle ( +- 0.11% ) (83.33%)
+ 5,076,835,183,223 stalled-cycles-frontend # 76.10% frontend cycles idle ( +- 0.11% ) (83.33%)
- 3,841,556,350,614 stalled-cycles-backend # 57.64% backend cycles idle ( +- 0.13% ) (66.67%)
+ 3,852,823,974,333 stalled-cycles-backend # 57.75% backend cycles idle ( +- 0.12% ) (66.67%)
- 4,148,398,171,079 instructions # 0.62 insn per cycle
+ 4,148,997,156,059 instructions # 0.62 insn per cycle
- # 1.22 stalled cycles per insn ( +- 0.10% ) (83.33%)
+ # 1.22 stalled cycles per insn ( +- 0.11% ) (83.33%)
- 887,187,118,591 branches # 401.943 M/sec ( +- 0.09% ) (83.33%)
+ 887,271,341,121 branches # 400.882 M/sec ( +- 0.11% ) (83.33%)
- 30,139,439,034 branch-misses # 3.40% of all branches ( +- 0.09% ) (83.33%)
+ 30,134,864,997 branch-misses # 3.40% of all branches ( +- 0.06% ) (83.33%)
- 275.904405540 seconds time elapsed ( +- 0.69% )
+ 276.660352016 seconds time elapsed ( +- 0.73% )
allmodconfig vmlinux size grows by a ~1Kb but that's fine - we optimize
our calling of the clear_page variants.
text data bss dec hex filename
9051979 23067670 27009024 59128673 3863b61 vmlinux
9053000 23067670 27009024 59129694 3863f5e vmlinux.clear_page
Reported-by: kernel test robot <fengguang.wu@intel.com>
Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170215111927.emdgxf2pide3kwro@pd.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/clear_page_64.S | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S index 5e2af3a88cf5..81b1635d67de 100644 --- a/arch/x86/lib/clear_page_64.S +++ b/arch/x86/lib/clear_page_64.S @@ -14,20 +14,15 @@ * Zero a page. * %rdi - page */ -ENTRY(clear_page) - - ALTERNATIVE_2 "jmp clear_page_orig", "", X86_FEATURE_REP_GOOD, \ - "jmp clear_page_c_e", X86_FEATURE_ERMS - +ENTRY(clear_page_rep) movl $4096/8,%ecx xorl %eax,%eax rep stosq ret -ENDPROC(clear_page) -EXPORT_SYMBOL(clear_page) +ENDPROC(clear_page_rep) +EXPORT_SYMBOL_GPL(clear_page_rep) ENTRY(clear_page_orig) - xorl %eax,%eax movl $4096/64,%ecx .p2align 4 @@ -47,10 +42,12 @@ ENTRY(clear_page_orig) nop ret ENDPROC(clear_page_orig) +EXPORT_SYMBOL_GPL(clear_page_orig) -ENTRY(clear_page_c_e) +ENTRY(clear_page_erms) movl $4096,%ecx xorl %eax,%eax rep stosb ret -ENDPROC(clear_page_c_e) +ENDPROC(clear_page_erms) +EXPORT_SYMBOL_GPL(clear_page_erms) |