如何使用樹莓派時鐘計數進行性能測量

Question

我在Raspberry Pi上進行性能測量，並希望獲得更高的分辨率，然後只是clock_gettime（）。

因此，我需要啓用CPU寄存器PMUSERENR。

根據我的Raspberry Pi上的/ proc/cpuinfo，我有一個「ARMv7處理器rev 5（v7l）」。所以，我下載的架構參考手冊，發現我必須使用：

CRn的= C9，OPC1 = 0，CRM = C14，OPC2 = 0

asm ("MCR p15, 0, %0, C9, C14, 0\n\t" :: "r"(1)); 

但一個內核模塊中使用此代碼時，我得到以下哎呀：

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.604846] Internal error: Oops: 5 [#1] SMP ARM 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.715199] Process insmod (pid: 2944, stack limit = 0xac80e210) 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.722399] Stack: (0xac80fe90 to 0xac810000) 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.727920] fe80:          7f1ba0f8 00007fff 80098128 ac80fea8 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.738472] fea0: 80578128 0000002d 00000000 7f1ba0f8 7f1ba0f8 7f1ba26c 7f1ba264 7f1ba134 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.749092] fec0: ac80e000 8057608c ac80feec ac80fed8 8057608c 00000000 00000000 00000000 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.759724] fee0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
pi@raspberrypi ~/projects/timer $ 
Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.770389] ff00: 00000000 00000000 00000000 00000000 76f5e948 00007390 00000000 76f7b390 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.781147] ff20: 76f5e948 b91a2390 ac80e000 00000000 ac80ffa4 ac80ff40 8009b6c4 80099714 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.792000] ff40: b919b000 00007390 b91a0598 b91a0457 b91a22c8 0000026c 000002ac 00000000 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.802930] ff60: 00000000 00000000 0000001f 00000020 0000000c 0000000a 00000009 00000000 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.813947] ff80: 7ea4371c 00000000 55afc028 00000080 8000fc28 ac80e000 00000000 ac80ffa8 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.825056] ffa0: 8000fa20 8009b5f0 7ea4371c 00000000 76f74000 00007390 76f5e948 76f74000 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.836170] ffc0: 7ea4371c 00000000 55afc028 00000080 55afbf78 00007390 76f5e948 00000000 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.847338] ffe0: 00000000 7ea436c4 76f55fb4 76ec0534 60000010 76f74000 00000000 00000000 

Message from syslogd@raspberrypi at Apr 29 20:58:12 ... 
kernel:[ 84.880715] Code: e51b3084 e1530005 e2455008 0a000009 (e5953014) 

我是新內核模塊，所以我不知道我應該去哪個方向。有沒有一種好的方法來調試這些東西？

Answer 1

Linux內核附帶一個PMU驅動程序。你可以利用它。我會爲你寫一篇教程，但爲什麼重新發明輪子，當這傢伙解釋得這麼好： http://www.carbondesignsystems.com/virtual-prototype-blog/using-the-arm-performance-monitor-unit-pmu-linux-driver