Re: [PATCH RFC] x86:Improve memset with general 64bit instruction

From: Ling Ma
Date: Tue Apr 08 2014 - 10:07:00 EST

Andi,

The below is compared result on older machine(cpu info is attached):
That shows new code get better performance up to 1.6x.

Bytes: ORG_TIME: NEW_TIME: ORG vs NEW:
7 0.87 0.76 1.14
16 0.99 0.68 1.45
18 1.07 0.77 1.38
21 1.09 0.78 1.39
25 1.11 0.77 1.44
30 1.12 0.73 1.53
36 1.15 0.75 1.53
38 1.12 0.75 1.49
62 1.18 0.77 1.53
75 1.25 0.79 1.58
85 1.28 0.80 1.60
120 1.33 0.82 1.62
193 1.45 0.88 1.64
245 1.48 0.96 1.54
256 1.45 0.90 1.61
356 1.61 1.02 1.57
601 1.78 1.22 1.45
958 2.04 1.47 1.38
1024 2.07 1.48 1.39
2048 2.80 2.21 1.26

Thanks
Ling

2014-04-08 0:42 GMT+08:00, Andi Kleen <andi@xxxxxxxxxxxxxx>:
> ling.ma.program@xxxxxxxxx writes:
>
>> From: Ling Ma <ling.ml@xxxxxxxxxxxxxxx>
>>
>> In this patch we manage to reduce miss branch prediction by
>> avoiding using branch instructions and force destination to be aligned
>> with general 64bit instruction.
>> Below compared results shows we improve performance up to 1.8x
>> (We modified test suit from Ondra, send after this patch)
>
> You didn't specify the CPU?
>
> I assume it's some Atom, as nothing else uses these open coded functions
> anymore?
>
> -Andi
>
> --
> ak@xxxxxxxxxxxxxxx -- Speaking for myself only
>
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4658.27
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:

processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 1
siblings : 4
core id : 0
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4655.03
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:

processor : 2
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 2
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4655.00
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:

processor : 3
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 1
siblings : 4
core id : 2
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4654.53
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:

processor : 4
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 1
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4655.02
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:

processor : 5
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 1
siblings : 4
core id : 1
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4654.97
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:

processor : 6
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 3
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4655.00
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:

processor : 7
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
stepping : 10
cpu MHz : 2327.506
cache size : 6144 KB
physical id : 1
siblings : 4
core id : 3
cpu cores : 4
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4655.01
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management: