How BogoMips is calculated in linux kernel?
阿新 • • 發佈:2022-03-10
How BogoMips is calculated in linux kernel? - Stack Overflow
/* * Standalone BogoMips program * * Based on code Linux kernel code in init/main.c and * include/linux/delay.h * * For more information on interpreting the results, see the BogoMIPS * Mini-HOWTO document. * * version: 1.3 * author: Jeff Tranter ([email protected])View Code*/ #include <stdio.h> #include <time.h> #ifdef CLASSIC_BOGOMIPS /* the original code from the Linux kernel */ static __inline__ void delay(int loops) { __asm__(".align 2,0x90\n1:\tdecl %0\n\tjns 1b": :"a" (loops):"ax"); } #endif #ifdef QNX_BOGOMIPS /* version for QNX C compiler */ void delay(intloops); #pragma aux delay = \ "l1:" \ "dec eax" \ "jns l1" \ parm nomemory [eax] modify exact nomemory [eax]; #endif #ifdef PORTABLE_BOGOMIPS /* portable version */ static void delay(int loops) { long i; for (i = loops; i >= 0 ; i--) ; } #endif int main(void) { unsigned long loops_per_sec = 1; unsigned long ticks; printf("Calibrating delay loop.. "); fflush(stdout); while ((loops_per_sec <<= 1)) { ticks = clock(); delay(loops_per_sec); ticks = clock() - ticks; if (ticks >= CLOCKS_PER_SEC) { loops_per_sec = (loops_per_sec / ticks) * CLOCKS_PER_SEC; printf("ok - %lu.%02lu BogoMips\n", loops_per_sec/500000, (loops_per_sec/5000) % 100 ); return 0; } } printf("failed\n"); return -1; }
BogoMIPS - LinuxMIPS (linux-mips.org)
.set noreorder loop: bnez $reg, loop subu $reg, 1 .set reorder"
怪不得BogoMIPS上不去,100發射也沒用啊。:-) 所以我之前把人看扁了,說錯了,放厥詞了。
However, 就FritzChess而言,單核效能提升不明顯啊,所以我也不能算是大錯特錯。
.set noreorder prevents the assembler from juggling the code sequence to move useful instructions into the branch delay slot. 還明確規定不許亂序執行。