Re: [PATCH RFC] [INET]: Get cirtical word in first 64bit of cache line

Ling Ma
2012-12-02T13:25:06Z

[-- Attachment #1: Type: text/plain, Size: 410 bytes --]

Hi Eric,

Attached benchmark test-cwf.c(cc -o test-cwf test-cwf.c), the result
shows when last level cache(LLC) miss and CPU fetches data from
memory, critical word as first 64bit member in cache line has better
performance(costs 158290336 cycles ) than other positions(offset 0x10,
costs 164100732 ) in cache line, the performance is improved by 3.6%
in this case.
cpu-info is also involved too.

Thanks
Ling

[-- Attachment #2: test-cwf.c --]
[-- Type: text/x-csrc, Size: 1986 bytes --]

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<unistd.h>
#define MAX_BUF_NUM (1 << 20)
#define MAX_BUF_SIZE (1 << 8)
#define ACCESS_OFFSET (0x10)

# define HP_TIMING_NOW(Var) \
({ unsigned long long _hi, _lo; \
asm volatile ("rdtsc" : "=a" (_lo), "=d" (_hi)); \
(Var) = _hi << 32 | _lo; })

#define repeat_times (64)

static void init_buf(char **buf)
{
int i = 0;
char *start;
char *end;
int pagesize = getpagesize();
*buf = malloc(MAX_BUF_SIZE * MAX_BUF_NUM + pagesize);
if(*buf == NULL) {
printf("\nfait to malloc space!\n");
exit(1);
} else {
*buf = *buf + pagesize;
*buf = (char *)(((unsigned long)*buf) & (-pagesize));
}

start = *buf;
end = *buf + (MAX_BUF_SIZE * MAX_BUF_NUM) - MAX_BUF_SIZE;

while(1) {
*((unsigned char **)start) = end;
*((unsigned char **)(start + ACCESS_OFFSET)) = (end + ACCESS_OFFSET);
start = start + MAX_BUF_SIZE;
if(start == end)
break;
*((unsigned char **)end) = start;
*((unsigned char **)(end + ACCESS_OFFSET)) = start + ACCESS_OFFSET;
end = end - MAX_BUF_SIZE;
}

}

unsigned long lookingup_memmory(char *access, int num)
{
__asm__("sub $1, %rsi");
__asm__("xor %rax, %rax");
__asm__("1:");
__asm__("mov (%rdi), %r8");
__asm__("add %r8, %rax");
__asm__("mov %r8, %rdi");
__asm__("sub $1, %rsi");
__asm__("jae 1b");
}

static unsigned long test_lookup_time(char *buf)
{
unsigned long i, start, end, best_time = ~0;

for(i = 0; i < repeat_times; i++) {
HP_TIMING_NOW(start);
lookingup_memmory(buf, MAX_BUF_NUM);
HP_TIMING_NOW(end);
if(best_time > (end - start))
best_time = (end - start);
}

return best_time;

}
void main (void)
{
char *buf1 = NULL;
char *buf2 = NULL;
unsigned long aligned_time, unaligned_time;

init_buf(&buf1);
init_buf(&buf2);

aligned_time = test_lookup_time(buf1);
unaligned_time = test_lookup_time(buf2 + ACCESS_OFFSET);

printf("looking-up aligned time %ld, looking-up unaligned time %ld\n", aligned_time, unaligned_time);
}

[-- Attachment #3: cpu-info --]
[-- Type: application/octet-stream, Size: 7050 bytes --]

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 1
cpu cores : 4
apicid : 2
initial apicid : 2
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

processor : 2
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 9
cpu cores : 4
apicid : 18
initial apicid : 18
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

processor : 3
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 10
cpu cores : 4
apicid : 20
initial apicid : 20
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

processor : 4
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
apicid : 1
initial apicid : 1
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

processor : 5
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 1
cpu cores : 4
apicid : 3
initial apicid : 3
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

processor : 6
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 9
cpu cores : 4
apicid : 19
initial apicid : 19
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

processor : 7
vendor_id : GenuineIntel
cpu family : 6
model : 44
model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
stepping : 2
microcode : 0x10
cpu MHz : 2400.005
cache size : 12288 KB
physical id : 0
siblings : 8
core id : 10
cpu cores : 4
apicid : 21
initial apicid : 21
fpu : yes
fpu_exception : yes
cpuid level : 11
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 pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt aes lahf_lm arat epb dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips : 4800.01
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual