英特尔Broadwell处理器经历了显着的FMA性能异常
Use*_*973 35 performance x86 assembly intel fma
代码1:
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel1: vfmadd231ps ymm0, ymm0, ymm0 vfmadd231ps ymm1, ymm1, ymm1 vfmadd231ps ymm2, ymm2, ymm2 vfmadd231ps ymm3, ymm3, ymm3 vfmadd231ps ymm4, ymm4, ymm4 vfmadd231ps ymm5, ymm5, ymm5 vfmadd231ps ymm6, ymm6, ymm6 vfmadd231ps ymm7, ymm7, ymm7 vfmadd231ps ymm8, ymm8, ymm8 vfmadd231ps ymm9, ymm9, ymm9 vpaddd ymm10, ymm10, ymm10 vpaddd ymm11, ymm11, ymm11 vpaddd ymm12, ymm12, ymm12 vpaddd ymm13, ymm13, ymm13 vpaddd ymm14, ymm14, ymm14 dec rcx jnz startLabel1代码2:
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel2: vmulps ymm0, ymm0, ymm0 vmulps ymm1, ymm1, ymm1 vmulps ymm2, ymm2, ymm2 vmulps ymm3, ymm3, ymm3 vmulps ymm4, ymm4, ymm4 vmulps ymm5, ymm5, ymm5 vmulps ymm6, ymm6, ymm6 vmulps ymm7, ymm7, ymm7 vmulps ymm8, ymm8, ymm8 vmulps ymm9, ymm9, ymm9 vpaddd ymm10, ymm10, ymm10 vpaddd ymm11, ymm11, ymm11 vpaddd ymm12, ymm12, ymm12 vpaddd ymm13, ymm13, ymm13 vpaddd ymm14, ymm14, ymm14 dec rcx jnz startLabel2Code3(与Code2相同,但具有长VEX前缀):
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel3: byte 0c4h, 0c1h, 07ch, 059h, 0c0h ;long VEX form vmulps ymm0, ymm0, ymm0 byte 0c4h, 0c1h, 074h, 059h, 0c9h ;long VEX form vmulps ymm1, ymm1, ymm1 byte 0c4h, 0c1h, 06ch, 059h, 0d2h ;long VEX form vmulps ymm2, ymm2, ymm2 byte 0c4h, 0c1h, 06ch, 059h, 0dbh ;long VEX form vmulps ymm3, ymm3, ymm3 byte 0c4h, 0c1h, 05ch, 059h, 0e4h ;long VEX form vmulps ymm4, ymm4, ymm4 byte 0c4h, 0c1h, 054h, 059h, 0edh ;long VEX form vmulps ymm5, ymm5, ymm5 byte 0c4h, 0c1h, 04ch, 059h, 0f6h ;long VEX form vmulps ymm6, ymm6, ymm6 byte 0c4h, 0c1h, 044h, 059h, 0ffh ;long VEX form vmulps ymm7, ymm7, ymm7 vmulps ymm8, ymm8, ymm8 vmulps ymm9, ymm9, ymm9 vpaddd ymm10, ymm10, ymm10 vpaddd ymm11, ymm11, ymm11 vpaddd ymm12, ymm12, ymm12 vpaddd ymm13, ymm13, ymm13 vpaddd ymm14, ymm14, ymm14 dec rcx jnz startLabel3Code4(与Code1相同,但带有xmm寄存器):
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel4: vfmadd231ps xmm0, xmm0, xmm0 vfmadd231ps xmm1, xmm1, xmm1 vfmadd231ps xmm2, xmm2, xmm2 vfmadd231ps xmm3, xmm3, xmm3 vfmadd231ps xmm4, xmm4, xmm4 vfmadd231ps xmm5, xmm5, xmm5 vfmadd231ps xmm6, xmm6, xmm6 vfmadd231ps xmm7, xmm7, xmm7 vfmadd231ps xmm8, xmm8, xmm8 vfmadd231ps xmm9, xmm9, xmm9 vpaddd xmm10, xmm10, xmm10 vpaddd xmm11, xmm11, xmm11 vpaddd xmm12, xmm12, xmm12 vpaddd xmm13, xmm13, xmm13 vpaddd xmm14, xmm14, xmm14 dec rcx jnz startLabel4Code5(与Code1相同,但具有非零的vpsubd):
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel5: vfmadd231ps ymm0, ymm0, ymm0 vfmadd231ps ymm1, ymm1, ymm1 vfmadd231ps ymm2, ymm2, ymm2 vfmadd231ps ymm3, ymm3, ymm3 vfmadd231ps ymm4, ymm4, ymm4 vfmadd231ps ymm5, ymm5, ymm5 vfmadd231ps ymm6, ymm6, ymm6 vfmadd231ps ymm7, ymm7, ymm7 vfmadd231ps ymm8, ymm8, ymm8 vfmadd231ps ymm9, ymm9, ymm9 vpsubd ymm10, ymm10, ymm11 vpsubd ymm11, ymm11, ymm12 vpsubd ymm12, ymm12, ymm13 vpsubd ymm13, ymm13, ymm14 vpsubd ymm14, ymm14, ymm10 dec rcx jnz startLabel5Code6b :(仅修改了vpaddds的内存操作数)
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel6: vfmadd231ps ymm0, ymm0, ymm0 vfmadd231ps ymm1, ymm1, ymm1 vfmadd231ps ymm2, ymm2, ymm2 vfmadd231ps ymm3, ymm3, ymm3 vfmadd231ps ymm4, ymm4, ymm4 vfmadd231ps ymm5, ymm5, ymm5 vfmadd231ps ymm6, ymm6, ymm6 vfmadd231ps ymm7, ymm7, ymm7 vfmadd231ps ymm8, ymm8, ymm8 vfmadd231ps ymm9, ymm9, ymm9 vpaddd ymm10, ymm10, [mem] vpaddd ymm11, ymm11, [mem] vpaddd ymm12, ymm12, [mem] vpaddd ymm13, ymm13, [mem] vpaddd ymm14, ymm14, [mem] dec rcx jnz startLabel6Code7 :(与Code1相同,但vpaddds使用ymm15)
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel7: vfmadd231ps ymm0, ymm0, ymm0 vfmadd231ps ymm1, ymm1, ymm1 vfmadd231ps ymm2, ymm2, ymm2 vfmadd231ps ymm3, ymm3, ymm3 vfmadd231ps ymm4, ymm4, ymm4 vfmadd231ps ymm5, ymm5, ymm5 vfmadd231ps ymm6, ymm6, ymm6 vfmadd231ps ymm7, ymm7, ymm7 vfmadd231ps ymm8, ymm8, ymm8 vfmadd231ps ymm9, ymm9, ymm9 vpaddd ymm10, ymm15, ymm15 vpaddd ymm11, ymm15, ymm15 vpaddd ymm12, ymm15, ymm15 vpaddd ymm13, ymm15, ymm15 vpaddd ymm14, ymm15, ymm15 dec rcx jnz startLabel7Code8 :(与Code7相同,但使用xmm而不是ymm)
Run Code Online (Sandbox Code Playgroud)vzeroall mov rcx, 1000000 startLabel8: vfmadd231ps xmm0, ymm0, ymm0 vfmadd231ps xmm1, xmm1, xmm1 vfmadd231ps xmm2, xmm2, xmm2 vfmadd231ps xmm3, xmm3, xmm3 vfmadd231ps xmm4, xmm4, xmm4 vfmadd231ps xmm5, xmm5, xmm5 vfmadd231ps xmm6, xmm6, xmm6 vfmadd231ps xmm7, xmm7, xmm7 vfmadd231ps xmm8, xmm8, xmm8 vfmadd231ps xmm9, xmm9, xmm9 vpaddd xmm10, xmm15, xmm15 vpaddd xmm11, xmm15, xmm15 vpaddd xmm12, xmm15, xmm15 vpaddd xmm13, xmm15, xmm15 vpaddd xmm14, xmm15, xmm15 dec rcx jnz startLabel8
禁用Turbo和C1E时测量的TSC时钟:
Haswell Broadwell Skylake
CPUID 306C3, 40661 306D4, 40671 506E3
Code1 ~5000000 ~7730000 ->~54% slower ~5500000 ->~10% slower
Code2 ~5000000 ~5000000 ~5000000
Code3 ~6000000 ~5000000 ~5000000
Code4 ~5000000 ~7730000 ~5500000
Code5 ~5000000 ~7730000 ~5500000
Code6b ~5000000 ~8380000 ~5500000
Code7 ~5000000 ~5000000 ~5000000
Code8 ~5000000 ~5000000 ~5000000
有人可以解释Broadwell上的Code1会发生什么吗？
我的猜测是Broadwell在Code1案例中以某种方式用vpaddds污染了Port1,但是只有当Port0和Port1已满时Haswell才能使用Port5;你有任何想法用FMA指令在Broadwell上完成~5000000 clk吗？
我试着重新排序.双和qword的相似行为;
我使用的是Windows 8.1和Win 10;
更新:
添加Code3作为Marat Dukhan的长期VEX的想法;
使用Skylake经验扩展结果表;
在此处上传了VS2015社区+ MASM示例代码
UPDATE2:
我尝试使用xmm寄存器而不是ymm(代码4).Broadwell的结果相同.
UPDATE3:
我添加了Code5作为Peter Cordes的想法(将vpaddd替换为其他intructions(vpxor,vpor,vpand,vpandn,vpsubd)).如果新指令不是归零惯用法(vpxor,vpsubd具有相同的寄存器),则结果在BDW上是相同的.使用Code4和Code5更新了示例项目.
UPDATE4:
我添加了Code6作为Stephen Canon的想法(内存操作数).结果是~8200000 clks.使用Code6更新示例项目;
我检查了CPU频率以及可能与AIDA64的系统稳定性测试有关的问题.频率稳定,没有节流迹象;
英特尔IACA 2.1 Haswell吞吐量分析:
Run Code Online (Sandbox Code Playgroud)Intel(R) Architecture Code Analyzer Version - 2.1 Analyzed File - Assembly.obj Binary Format - 64Bit Architecture - HSW Analysis Type - Throughput Throughput Analysis Report -------------------------- Block Throughput: 5.10 Cycles Throughput Bottleneck: Port0, Port1, Port5 Port Binding In Cycles Per Iteration: --------------------------------------------------------------------------------------- | Port | 0 - DV | 1 | 2 - D | 3 - D | 4 | 5 | 6 | 7 | --------------------------------------------------------------------------------------- | Cycles | 5.0 0.0 | 5.0 | 0.0 0.0 | 0.0 0.0 | 0.0 | 5.0 | 1.0 | 0.0 | --------------------------------------------------------------------------------------- | Num Of | Ports pressure in cycles | | | Uops | 0 - DV | 1 | 2 - D | 3 - D | 4 | 5 | 6 | 7 | | --------------------------------------------------------------------------------- | 1 | 1.0 | | | | | | | | CP | vfmadd231ps ymm0, ymm0, ymm0 | 1 | | 1.0 | | | | | | | CP | vfmadd231ps ymm1, ymm1, ymm1 | 1 | 1.0 | | | | | | | | CP | vfmadd231ps ymm2, ymm2, ymm2 | 1 | | 1.0 | | | | | | | CP | vfmadd231ps ymm3, ymm3, ymm3 | 1 | 1.0 | | | | | | | | CP | vfmadd231ps ymm4, ymm4, ymm4 | 1 | | 1.0 | | | | | | | CP | vfmadd231ps ymm5, ymm5, ymm5 | 1 | 1.0 | | | | | | | | CP | vfmadd231ps ymm6, ymm6, ymm6 | 1 | | 1.0 | | | | | | | CP | vfmadd231ps ymm7, ymm7, ymm7 | 1 | 1.0 | | | | | | | | CP | vfmadd231ps ymm8, ymm8, ymm8 | 1 | | 1.0 | | | | | | | CP | vfmadd231ps ymm9, ymm9, ymm9 | 1 | | | | | | 1.0 | | | CP | vpaddd ymm10, ymm10, ymm10 | 1 | | | | | | 1.0 | | | CP | vpaddd ymm11, ymm11, ymm11 | 1 | | | | | | 1.0 | | | CP | vpaddd ymm12, ymm12, ymm12 | 1 | | | | | | 1.0 | | | CP | vpaddd ymm13, ymm13, ymm13 | 1 | | | | | | 1.0 | | | CP | vpaddd ymm14, ymm14, ymm14 | 1 | | | | | | | 1.0 | | | dec rcx | 0F | | | | | | | | | | jnz 0xffffffffffffffaa Total Num Of Uops: 16我遵循了jcomeau_ictx的想法,并修改了Agner Fog的testp.zip(2015-12-22发布)BDW 306D4上的端口使用情况:
Run Code Online (Sandbox Code Playgroud)Clock Core cyc Instruct uop p0 uop p1 uop p5 uop p6 Code1: 7734720 7734727 17000001 4983410 5016592 5000001 1000001 Code2: 5000072 5000072 17000001 5000010 5000014 4999978 1000002港口分布近乎完美的Haswell.然后我检查了资源停滞计数器(事件0xa2)
Run Code Online (Sandbox Code Playgroud)Clock Core cyc Instruct res.stl. RS stl. SB stl. ROB stl. Code1: 7736212 7736213 17000001 3736191 3736143 0 0 Code2: 5000068 5000072 17000001 1000050 999957 0 0在我看来,Code1和Code2的差异来自RS档.来自英特尔SDM的备注:"由于没有合格的RS条目,Cycles停滞不前."
我怎样才能通过FMA避免这种失速？
Update5:
Code6改变了,正如Peter Cordes引起我的注意,只有vpaddds使用内存操作数.对HSW和SKL没有影响,BDW变得更糟.
正如Marat Dukhan测量的那样,不仅vpadd/vpsub/vpand/vpandn/vpxor受到影响,而且还有其他Port5限制性指令,如vmovaps,vblendps,vpermps,vshufps,vbroadcastss;
正如IwillnotexistIdonotexist建议的那样,我尝试了其他操作数.一个成功的修改是Code7,其中所有vpaddds都使用ymm15.这个版本可以生成BDW~5000000 clks,但只是一段时间.在大约600万FMA对之后它达到了通常的~7730000 clks:
Run Code Online (Sandbox Code Playgroud)Clock Core cyc Instruct res.stl. RS stl. SB stl. ROB stl. 5133724 5110723 17000001 1107998 946376 0 0 6545476 6545482 17000001 2545453 1 0 0 6545468 6545471 17000001 2545437 90910 0 0 5000016 5000019 17000001 999992 999992 0 0 7671620 7617127 17000003 3614464 3363363 0 0 7737340 7737345 17000001 3737321 3737259 0 0 7802916 7747108 17000003 3737478 3735919 0 0 7928784 7796057 17000007 3767962 3676744 0 0 7941072 7847463 17000003 3781103 3651595 0 0 7787812 7779151 17000005 3765109 3685600 0 0 7792524 7738029 17000002 3736858 3736764 0 0 7736000 7736007 17000001 3735983 3735945 0 0我尝试将Code7的xmm版本作为Code8.效果类似,但运行时间越长,持续时间越长.我没有发现1.6GHz i5-5250U和3.7GHz i7-5775C之间存在显着差异.
16和17是在禁用超线程的情况下完成的.启用HTT后,效果会更差.
Iwi*_*ist 17
Updated
I've got no explanation for you, since I'm on Haswell, but I do have code to share that might help you or someone else with Broadwell or Skylake hardware isolate your problem. If you could please run it on your machine and share the results, we could gain an insight into what's happening to your machine.
Intro
Recent Intel Core i7 processors have 7 performance monitor counters (PMCs), 3 fixed-function and 4 general-purpose, that may be used to profile code. The fixed-function PMCs are:
- Instructions retired
- Unhalted core cycles (Clock ticks including the effects of TurboBoost)
- Unhalted Reference cycles (Fixed-frequency clock ticks)
The ratio of core:reference clock cycles determines the relative speedup or slowdown from dynamic frequency scaling.
Although software exists (see comments below) that accesses these counters, I did not know them and still find them to be insufficiently fine-grained.
I therefore wrote myself a Linux kernel module, perfcount, over the past few days to grant me access to the Intel performance counter monitors, and a userspace testbench and library for your code that wraps your FMA code around calls to my LKM. Instructions for how to reproduce my setup will follow.
My testbench source code is below. It warms up, then runs your code several times, testing it over a long list of metrics. I changed your loop count to 1 billion. Because only 4 general-purpose PMCs can be programmed at once, I do the measurements 4 at a time.
perfcountdemo.c
/* Includes */
#include "libperfcount.h"
#include <ctype.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Function prototypes */
void code1(void);
void code2(void);
void code3(void);
void code4(void);
void code5(void);
/* Global variables */
void ((*FN_TABLE[])(void)) = {
code1,
code2,
code3,
code4,
code5
};
/**
* Code snippets to bench
*/
void code1(void){
asm volatile(
".intel_syntax noprefix\n\t"
"vzeroall\n\t"
"mov rcx, 1000000000\n\t"
"LstartLabel1:\n\t"
"vfmadd231ps %%ymm0, %%ymm0, %%ymm0\n\t"
"vfmadd231ps ymm1, ymm1, ymm1\n\t"
"vfmadd231ps ymm2, ymm2, ymm2\n\t"
"vfmadd231ps ymm3, ymm3, ymm3\n\t"
"vfmadd231ps ymm4, ymm4, ymm4\n\t"
"vfmadd231ps ymm5, ymm5, ymm5\n\t"
"vfmadd231ps ymm6, ymm6, ymm6\n\t"
"vfmadd231ps ymm7, ymm7, ymm7\n\t"
"vfmadd231ps ymm8, ymm8, ymm8\n\t"
"vfmadd231ps ymm9, ymm9, ymm9\n\t"
"vpaddd ymm10, ymm10, ymm10\n\t"
"vpaddd ymm11, ymm11, ymm11\n\t"
"vpaddd ymm12, ymm12, ymm12\n\t"
"vpaddd ymm13, ymm13, ymm13\n\t"
"vpaddd ymm14, ymm14, ymm14\n\t"
"dec rcx\n\t"
"jnz LstartLabel1\n\t"
".att_syntax noprefix\n\t"
: /* No outputs we care about */
: /* No inputs we care about */
: "xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7",
"xmm8", "xmm9", "xmm10", "xmm11", "xmm12", "xmm13", "xmm14", "xmm15",
"rcx",
"memory"
);
}
void code2(void){
}
void code3(void){
}
void code4(void){
}
void code5(void){
}
/* Test Schedule */
const char* const SCHEDULE[] = {
/* Batch */
"uops_issued.any",
"uops_issued.any<1",
"uops_issued.any>=1",
"uops_issued.any>=2",
/* Batch */
"uops_issued.any>=3",
"uops_issued.any>=4",
"uops_issued.any>=5",
"uops_issued.any>=6",
/* Batch */
"uops_executed_port.port_0",
"uops_executed_port.port_1",
"uops_executed_port.port_2",
"uops_executed_port.port_3",
/* Batch */
"uops_executed_port.port_4",
"uops_executed_port.port_5",
"uops_executed_port.port_6",
"uops_executed_port.port_7",
/* Batch */
"resource_stalls.any",
"resource_stalls.rs",
"resource_stalls.sb",
"resource_stalls.rob",
/* Batch */
"uops_retired.all",
"uops_retired.all<1",
"uops_retired.all>=1",
"uops_retired.all>=2",
/* Batch */
"uops_retired.all>=3",
"uops_retired.all>=4",
"uops_retired.all>=5",
"uops_retired.all>=6",
/* Batch */
"inst_retired.any_p",
"inst_retired.any_p<1",
"inst_retired.any_p>=1",
"inst_retired.any_p>=2",
/* Batch */
"inst_retired.any_p>=3",
"inst_retired.any_p>=4",
"inst_retired.any_p>=5",
"inst_retired.any_p>=6",
/* Batch */
"idq_uops_not_delivered.core",
"idq_uops_not_delivered.core<1",
"idq_uops_not_delivered.core>=1",
"idq_uops_not_delivered.core>=2",
/* Batch */
"idq_uops_not_delivered.core>=3",
"idq_uops_not_delivered.core>=4",
"rs_events.empty",
"idq.empty",
/* Batch */
"idq.mite_all_uops",
"idq.mite_all_uops<1",
"idq.mite_all_uops>=1",
"idq.mite_all_uops>=2",
/* Batch */
"idq.mite_all_uops>=3",
"idq.mite_all_uops>=4",
"move_elimination.int_not_eliminated",
"move_elimination.simd_not_eliminated",
/* Batch */
"lsd.uops",
"lsd.uops<1",
"lsd.uops>=1",
"lsd.uops>=2",
/* Batch */
"lsd.uops>=3",
"lsd.uops>=4",
"ild_stall.lcp",
"ild_stall.iq_full",
/* Batch */
"br_inst_exec.all_branches",
"br_inst_exec.0x81",
"br_inst_exec.0x82",
"icache.misses",
/* Batch */
"br_misp_exec.all_branches",
"br_misp_exec.0x81",
"br_misp_exec.0x82",
"fp_assist.any",
/* Batch */
"cpu_clk_unhalted.core_clk",
"cpu_clk_unhalted.ref_xclk",
"baclears.any"
};
const int NUMCOUNTS = sizeof(SCHEDULE)/sizeof(*SCHEDULE);
/**
* Main
*/
int main(int argc, char* argv[]){
int i;
/**
* Initialize
*/
pfcInit();
if(argc <= 1){
pfcDumpEvents();
exit(1);
}
pfcPinThread(3);
/**
* Arguments are:
*
* perfcountdemo #codesnippet
*
* There is a schedule of configuration that is followed.
*/
void (*fn)(void) = FN_TABLE[strtoull(argv[1], NULL, 0)];
static const uint64_t ZERO_CNT[7] = {0,0,0,0,0,0,0};
static const uint64_t ZERO_CFG[7] = {0,0,0,0,0,0,0};
uint64_t cnt[7] = {0,0,0,0,0,0,0};
uint64_t cfg[7] = {2,2,2,0,0,0,0};
/* Warmup */
for(i=0;i<10;i++){
fn();
}
/* Run master loop */
for(i=0;i<NUMCOUNTS;i+=4){
/* Configure counters */
const char* sched0 = i+0 < NUMCOUNTS ? SCHEDULE[i+0] : "";
const char* sched1 = i+1 < NUMCOUNTS ? SCHEDULE[i+1] : "";
const char* sched2 = i+2 < NUMCOUNTS ? SCHEDULE[i+2] : "";
const char* sched3 = i+3 < NUMCOUNTS ? SCHEDULE[i+3] : "";
cfg[3] = pfcParseConfig(sched0);
cfg[4] = pfcParseConfig(sched1);
cfg[5] = pfcParseConfig(sched2);
cfg[6] = pfcParseConfig(sched3);
pfcWrConfigCnts(0, 7, cfg);
pfcWrCountsCnts(0, 7, ZERO_CNT);
pfcRdCountsCnts(0, 7, cnt);
/* ^ Should report 0s, and launch the counters. */
/************** Hot section **************/
fn();
/************ End Hot section ************/
pfcRdCountsCnts(0, 7, cnt);
pfcWrConfigCnts(0, 7, ZERO_CFG);
/* ^ Should clear the counter config and disable them. */
/**
* Print the lovely results
*/
printf("Instructions Issued : %20llu\n", cnt[0]);
printf("Unhalted core cycles : %20llu\n", cnt[1]);
printf("Unhalted reference cycles : %20llu\n", cnt[2]);
printf("%-35s: %20llu\n", sched0, cnt[3]);
printf("%-35s: %20llu\n", sched1, cnt[4]);
printf("%-35s: %20llu\n", sched2, cnt[5]);
printf("%-35s: %20llu\n", sched3, cnt[6]);
}
/**
* Close up shop
*/
pfcFini();
}
On my machine, I got the following results:
Haswell Core i7-4700MQ
> ./perfcountdemo 0
Instructions Issued : 17000001807
Unhalted core cycles : 5305920785
Unhalted reference cycles : 4245764952
uops_issued.any : 16000811079
uops_issued.any<1 : 1311417889
uops_issued.any>=1 : 4000292290
uops_issued.any>=2 : 4000229358
Instructions Issued : 17000001806
Unhalted core cycles : 5303822082
Unhalted reference cycles : 4243345896
uops_issued.any>=3 : 4000156998
uops_issued.any>=4 : 4000110067
uops_issued.any>=5 : 0
uops_issued.any>=6 : 0
Instructions Issued : 17000001811
Unhalted core cycles : 5314227923
Unhalted reference cycles : 4252020624
uops_executed_port.port_0 : 5016261477
uops_executed_port.port_1 : 5036728509
uops_executed_port.port_2 : 5282
uops_executed_port.port_3 : 12481
Instructions Issued : 17000001816
Unhalted core cycles : 5329351248
Unhalted reference cycles : 4265809728
uops_executed_port.port_4 : 7087
uops_executed_port.port_5 : 4946019835
uops_executed_port.port_6 : 1000228324
uops_executed_port.port_7 : 1372
Instructions Issued : 17000001816
Unhalted core cycles : 5325153463
Unhalted reference cycles : 4261060248
resource_stalls.any : 1322734589
resource_stalls.rs : 844250210
resource_stalls.sb : 0
resource_stalls.rob : 0
Instructions Issued : 17000001814
Unhalted core cycles : 5327823817
Unhalted reference cycles : 4262914728
uops_retired.all : 16000445793
uops_retired.all<1 : 687284798
uops_retired.all>=1 : 4646263984
uops_retired.all>=2 : 4452324050
Instructions Issued : 17000001809
Unhalted core cycles : 5311736558
Unhalted reference cycles : 4250015688
uops_retired.all>=3 : 3545695253
uops_retired.all>=4 : 3341664653
uops_retired.all>=5 : 1016
uops_retired.all>=6 : 1
Instructions Issued : 17000001871
Unhalted core cycles : 5477215269
Unhalted reference cycles : 4383891984
inst_retired.any_p : 17000001871
inst_retired.any_p<1 : 891904306
inst_retired.any_p>=1 : 4593972062
inst_retired.any_p>=2 : 4441024510
Instructions Issued : 17000001835
Unhalted core cycles : 5377202052
Unhalted reference cycles : 4302895152
inst_retired.any_p>=3 : 3555852364
inst_retired.any_p>=4 : 3369559466
inst_retired.any_p>=5 : 999980244
inst_retired.any_p>=6 : 0
Instructions Issued : 17000001826
Unhalted core cycles : 5349373678
Unhalted reference cycles : 4280991912
idq_uops_not_delivered.core : 1580573
idq_uops_not_delivered.core<1 : 5354931839
idq_uops_not_delivered.core>=1 : 471248
idq_uops_not_delivered.core>=2 : 418625
Instructions Issued : 17000001808
Unhalted core cycles : 5309687640
Unhalted reference cycles : 4248083976
idq_uops_not_delivered.core>=3 : 280800
idq_uops_not_delivered.core>=4 : 247923
rs_events.empty : 0
idq.empty : 649944
Instructions Issued : 17000001838
Unhalted core cycles : 5392229041
Unhalted reference cycles : 4315704216
idq.mite_all_uops : 2496139
idq.mite_all_uops<1 : 5397877484
idq.mite_all_uops>=1 : 971582
idq.mite_all_uops>=2 : 595973
Instructions Issued : 17000001822
Unhalted core cycles : 5347205506
Unhalted reference cycles : 4278845208
idq.mite_all_uops>=3 : 394011
idq.mite_all_uops>=4 : 335205
move_elimination.int_not_eliminated: 0
move_elimination.simd_not_eliminated: 0
Instructions Issued : 17000001812
Unhalted core cycles : 5320621549
Unhalted reference cycles : 4257095280
lsd.uops : 15999287982
lsd.uops<1 : 1326629729
lsd.uops>=1 : 3999821996
lsd.uops>=2 : 3999821996
Instructions Issued : 17000001813
Unhalted core cycles : 5320533147
Unhalted reference cycles : 4257105096
lsd.uops>=3 : 3999823498
lsd.uops>=4 : 3999823498
ild_stall.lcp : 0
ild_stall.iq_full : 3468
Instructions Issued : 17000001813
Unhalted core cycles : 5323278281
Unhalted reference cycles : 4258969200
br_inst_exec.all_branches : 1000016626
br_inst_exec.0x81 : 1000016616
br_inst_exec.0x82 : 0
icache.misses : 294
Instructions Issued : 17000001812
Unhalted core cycles : 5315098728
Unhalted reference cycles : 4253082504
br_misp_exec.all_branches : 5
br_misp_exec.0x81 : 2
br_misp_exec.0x82 : 0
fp_assist.any : 0
Instructions Issued : 17000001819
Unhalted core cycles : 5338484610
Unhalted reference cycles : 4271432976
cpu_clk_unhalted.core_clk : 5338494250
cpu_clk_unhalted.ref_xclk : 177976806
baclears.any : 1
: 0
我们可能会看到Haswell,一切都很好.我将从上面的统计数据中做一些笔记:
- 发出的指令对我来说非常一致.它始终存在
17000001800,这是一个好兆头:这意味着我们可以很好地估计我们的开销.同意其他固定功能计数器.它们都匹配得相当好的事实意味着4个批次的测试是苹果对苹果的比较. - 核心:参考周期的比率约为5305920785/4245764952,我们得到的平均频率缩放为~1.25; 这与我的观察结果相吻合,我的核心时钟频率从2.4 GHz到3.0 GHz.
cpu_clk_unhalted.core_clk/(10.0*cpu_clk_unhalted.ref_xclk)也给出了不到3 GHz的频率. - The ratio of instructions issued to core cycles gives the IPC, 17000001807/5305920785 ~ 3.20, which is also about right: 2 FMA+1 VPADDD every clock cycle for 4 clock cycles, and 2 extra loop control instructions every 5th clock cycle that go in parallel.
uops_issued.any: The number of instructions issued is ~17B, but the number of uops issued is ~16B. That's because the two instructions for loop control are fusing together; Good sign. Moreover, around 1.3B clock cycles out of 5.3B (25% of the time), no uops were issued, while the near-totality of the rest of the time (4B clock cycles), 4 uops issued at a time.uops_executed_port.port_[0-7]: Port saturation. We're in good health. Of the 16B post-fusion uops, Ports 0, 1 and 5 ate 5B uops each over 5.3B cycles (Which means they were distributed optimally: Float, float, int respectively), Port 6 ate 1B (the fused dec-branch op), and ports 2, 3, 4 and 7 ate negligible amounts by comparison.resource_stalls: 1.3B of them occurred, 2/3 of which were due to the reservation station (RS) and the other third to unknown causes.- From the cumulative distribution we built with our comparisons on
uops_retired.allandinst_retired.all, we know we are retiring 4 uops 60% of the time, 0 uops 13% of the time and 2 uops the rest of the time, with negligible amounts otherwise. - (Numerous
*idq*counts): The IDQ only rarely holds us up. lsd: The Loop Stream Detector is working; Nearly 16B fused uops were supplied to the frontend from it.ild:指令长度解码不是瓶颈,并且不会遇到单个长度更改前缀.br_inst_exec/br_misp_exec:分支错误预测是一个可以忽略不计的问题.icache.misses:微不足道.fp_assist:微不足道.没有遇到异常.(我相信如果没有DAZ denormals-are-zero冲洗,他们需要一个辅助,这应该在这里注册)
因此,在英特尔Haswell上,它一帆风顺.如果你可以在你的机器上运行我的套件,那就太好了.
复制说明
- 规则#1:在使用它之前检查我的所有代码.千万不要盲目信任互联网上的陌生人.
- 抓住perfcountdemo.c,libperfcount.c和libperfcount.h,把它们放在同一个目录,并编译在一起.
- 抓住perfcount.c和Makefile文件,把它们放在同一个目录中,
make内核模块. - 使用GRUB引导标志重新启动计算机
nmi_watchdog=0 modprobe.blacklist=iTCO_wdt,iTCO_vendor_support.否则,NMI监管机构将篡改无线核心周期计数器. insmod perfcount.ko模块.dmesg | tail -n 10应该说它成功加载并说有3个Ff计数器和4个Gp计数器,否则就说明没有这样做了.- 运行我的应用程序,最好在系统的其余部分没有负载的情况下运行.尝试
perfcountdemo.c通过将参数更改为更改您限制亲缘关系的核心pfcPinThread(). - 在这里编辑结果.
- @Zboson我已经用我的机器上更多相关计数器的结果更新了答案,并将软件清理到了我认为它可能更广泛有用的地方,例如对于像你这样的人. (2认同)
Mar*_*han 11
更新:以前的版本包含6个VPADDD指令(问题中为5个),并且额外VPADDD导致Broadwell不平衡.修复后,Haswell,Broadwell和Skylake向端口0,1和5发出几乎相同数量的uop.
没有端口污染,但uops被安排在次优,大多数uops在Broadwell上进入端口5,并且在端口0和1饱和之前成为瓶颈.
为了演示正在发生的事情,我建议(ab)在PeachPy.IO上使用该演示:
在Google Chrome中打开www.peachpy.io(在其他浏览器中无法使用).
用下面的代码替换默认代码(实现SDOT功能),这实际上是移植到PeachPy语法的示例:
Run Code Online (Sandbox Code Playgroud)n = Argument(size_t) x = Argument(ptr(const_float_)) incx = Argument(size_t) y = Argument(ptr(const_float_)) incy = Argument(size_t) with Function("sdot", (n, x, incx, y, incy)) as function: reg_n = GeneralPurposeRegister64() LOAD.ARGUMENT(reg_n, n) VZEROALL() with Loop() as loop: for i in range(15): ymm_i = YMMRegister(i) if i < 10: VFMADD231PS(ymm_i, ymm_i, ymm_i) else: VPADDD(ymm_i, ymm_i, ymm_i) DEC(reg_n) JNZ(loop.begin) RETURN()我有许多不同微体系结构的机器作为PeachPy.io的后端.选择Intel Haswell,Intel Broadwell或Intel Skylake并按"Quick Run".系统将编译您的代码,将其上载到服务器,并可视化执行期间收集的性能计数器.
以下是Intel Haswell上执行端口的uops分布:
- 以下是英特尔布罗德威尔的情节:
- 显然,无论uops调度程序中的缺陷是什么,都是在英特尔Skylake中修复的,因为该机器上的端口压力与Haswell相同.
- @IwillnotexistIdonotexist @PeterCordes你可以获得原始事件计数.使用PeachPy在本地编译源文件为`python -m peachpy.x86_64 -mabi = sysv -mimage-format = elf -mcpu = haswell experiment.py -o experiment.o`,然后使用`wget`作为`wget上传 - header ="Content-Type:application/octet-stream"--post-file = experiment.o"http://www.peachpy.io/run/broadwell?kernel=sdot&n=1000&incx=1&incy=1&offx=0&offy=0 "-q -O -`.如果需要,用`haswell`或`skylake`替换`broadwell`. (3认同)
- @Marat Dukhan啊哈!*你确实有6个VPADDD*.尝试在范围(16)中替换`for i:`在范围(15)中使用`for i:`.有趣的是,HSW可以对这个额外的VPADDD进行负载平衡,而BRW则没有. (2认同)
- @IwillnotexistIdonotexist确实!没有注意到原始代码没有使用所有寄存器 (2认同)
- @MaratDukhan我仍然认为你的帖子非常有价值; 你已经清楚地表明,Haswell可以将`5 1/3`的VPADDDs跳入`p5`,将'2/3`的VPADDDs跳入`p1`,将'4 2/3`的FMA跳转到`p1`和`5 1/3`FMA成'p0`,而BRW看似不能.这值得提出自己的问题. (2认同)
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