资源简介
《深入理解计算机系统》一书的配套lab之malloc lab。学生用来实现自己的malloc, realloc和free函数。
Students implement their own versions of malloc, free, and realloc. This lab gives students a clear understanding of data layout and organization, and requires them to evaluate different trade-offs between space and time efficiency. One of our favorite labs. When students finish this one, they really understand pointers!
代码片段和文件信息
/*
* clock.c - Routines for using the cycle counters on x86
* Alpha and Sparc boxes.
*
* Copyright (c) 2002 R. Bryant and D. O‘Hallaron All rights reserved.
* May not be used modified or copied without permission.
*/
#include
#include
#include
#include
#include “clock.h“
/*******************************************************
* Machine dependent functions
*
* Note: the constants __i386__ and __alpha
* are set by GCC when it calls the C preprocessor
* You can verify this for yourself using gcc -v.
*******************************************************/
#if defined(__i386__)
/*******************************************************
* Pentium versions of start_counter() and get_counter()
*******************************************************/
/* $begin x86cyclecounter */
/* Initialize the cycle counter */
static unsigned cyc_hi = 0;
static unsigned cyc_lo = 0;
/* Set *hi and *lo to the high and low order bits of the cycle counter.
Implementation requires assembly code to use the rdtsc instruction. */
void access_counter(unsigned *hi unsigned *lo)
{
asm(“rdtsc; movl %%edx%0; movl %%eax%1“ /* Read cycle counter */
: “=r“ (*hi) “=r“ (*lo) /* and move results to */
: /* No input */ /* the two outputs */
: “%edx“ “%eax“);
}
/* Record the current value of the cycle counter. */
void start_counter()
{
access_counter(&cyc_hi &cyc_lo);
}
/* Return the number of cycles since the last call to start_counter. */
double get_counter()
{
unsigned ncyc_hi ncyc_lo;
unsigned hi lo borrow;
double result;
/* Get cycle counter */
access_counter(&ncyc_hi &ncyc_lo);
/* Do double precision subtraction */
lo = ncyc_lo - cyc_lo;
borrow = lo > ncyc_lo;
hi = ncyc_hi - cyc_hi - borrow;
result = (double) hi * (1 << 30) * 4 + lo;
if (result < 0) {
fprintf(stderr “Error: counter returns neg value: %.0f\n“ result);
}
return result;
}
/* $end x86cyclecounter */
#elif defined(__alpha)
/****************************************************
* Alpha versions of start_counter() and get_counter()
***************************************************/
/* Initialize the cycle counter */
static unsigned cyc_hi = 0;
static unsigned cyc_lo = 0;
/* Use Alpha cycle timer to compute cycles. Then use
measured clock speed to compute seconds
*/
/*
* counterRoutine is an array of Alpha instructions to access
* the Alpha‘s processor cycle counter. It uses the rpcc
* instruction to access the counter. This 64 bit register is
* divided into two parts. The lower 32 bits are the cycles
* used by the current process. The upper 32 bits are wall
* clock cycles. These instructions read the counter and
* convert the lower 32 bits into an unsigned int - this is the
* user space counter value.
* NOTE: The counter has a very limited time span. With a
* 450MhZ clock the c
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