linux灵活性太差了。。。。

se9en · 发表于 2008-7-9 17:53:52

对阿。我觉得最大的问题是minix3中貌似没有虚拟内存的概念。要人命阿。

zbw76 · 发表于 2008-7-9 23:40:08

3好多了,1 2都是教学用的,内存管理是我对这书唯一看了的代码,非常简单,比dos的都简单.
人家的目的是教学演示.还有, 1和2 都是收费的哦.不是gpl

zbw76 · 发表于 2008-7-9 23:46:51

alloc.c
2.04的,简洁明了吧,大师写的代码就是不一样,看着就是种享受.
不过原理很简单,就是找到一块足够大的空闲快,分出去.
碎片问题很严重的.

/* This file is concerned with allocating and freeing arbitrary-size blocks of
* physical memory on behalf of the FORK and EXEC system calls. The key data
* structure used is the hole table, which maintains a list of holes in memory.
* It is kept sorted in order of increasing memory address. The addresses
* it contains refer to physical memory, starting at absolute address 0
* (i.e., they are not relative to the start of MM). During system
* initialization, that part of memory containing the interrupt vectors,
* kernel, and MM are "allocated" to mark them as not available and to
* remove them from the hole list.
*
* The entry points into this file are:
* alloc_mem: allocate a given sized chunk of memory
* free_mem: release a previously allocated chunk of memory
* mem_init: initialize the tables when MM start up
* max_hole: returns the largest hole currently available
*/
#include "mm.h"
#include <minix/com.h>
#include <minix/callnr.h>
#include <signal.h>
#include "mproc.h"
#define NR_HOLES (2*NR_PROCS) /* max # entries in hole table */
#define NIL_HOLE (struct hole *) 0
PRIVATE struct hole {
struct hole *h_next; /* pointer to next entry on the list */
phys_clicks h_base; /* where does the hole begin? */
phys_clicks h_len; /* how big is the hole? */
} hole[NR_HOLES];
PRIVATE struct hole *hole_head; /* pointer to first hole */
PRIVATE struct hole *free_slots;/* ptr to list of unused table slots */
#if ENABLE_SWAP
PRIVATE int swap_fd = -1; /* file descriptor of open swap file/device */
PRIVATE u32_t swap_offset; /* offset to start of swap area on swap file */
PRIVATE phys_clicks swap_base; /* memory offset chosen as swap base */
PRIVATE phys_clicks swap_maxsize;/* maximum amount of swap "memory" possible */
PRIVATE struct mproc *in_queue; /* queue of processes wanting to swap in */
PRIVATE struct mproc *outswap = &mproc[LOW_USER]; /* outswap candidate? */
#else /* !SWAP */
#define swap_base ((phys_clicks) -1)
#endif /* !SWAP */
FORWARD _PROTOTYPE( void del_slot, (struct hole *prev_ptr, struct hole *hp) );
FORWARD _PROTOTYPE( void merge, (struct hole *hp) );
#if ENABLE_SWAP
FORWARD _PROTOTYPE( int swap_out, (void) );
#else
#define swap_out() (0)
#endif
/*===========================================================================*
* alloc_mem *
*===========================================================================*/
PUBLIC phys_clicks alloc_mem(clicks)
phys_clicks clicks; /* amount of memory requested */
{
/* Allocate a block of memory from the free list using first fit. The block
* consists of a sequence of contiguous bytes, whose length in clicks is
* given by 'clicks'. A pointer to the block is returned. The block is
* always on a click boundary. This procedure is called when memory is
* needed for FORK or EXEC. Swap other processes out if needed.
*/
register struct hole *hp, *prev_ptr;
phys_clicks old_base;
do {
hp = hole_head;
while (hp != NIL_HOLE && hp->h_base < swap_base) {
if (hp->h_len >= clicks) {
/* We found a hole that is big enough. Use it. */
old_base = hp->h_base; /* remember where it started */
hp->h_base += clicks; /* bite a piece off */
hp->h_len -= clicks; /* ditto */
/* Delete the hole if used up completely. */
if (hp->h_len == 0) del_slot(prev_ptr, hp);
/* Return the start address of the acquired block. */
return(old_base);
}
prev_ptr = hp;
hp = hp->h_next;
}
} while (swap_out()); /* try to swap some other process out */
return(NO_MEM);
}
/*===========================================================================*
* free_mem *
*===========================================================================*/
PUBLIC void free_mem(base, clicks)
phys_clicks base; /* base address of block to free */
phys_clicks clicks; /* number of clicks to free */
{
/* Return a block of free memory to the hole list. The parameters tell where
* the block starts in physical memory and how big it is. The block is added
* to the hole list. If it is contiguous with an existing hole on either end,
* it is merged with the hole or holes.
*/
register struct hole *hp, *new_ptr, *prev_ptr;
if (clicks == 0) return;
if ( (new_ptr = free_slots) == NIL_HOLE) panic("Hole table full", NO_NUM);
new_ptr->h_base = base;
new_ptr->h_len = clicks;
free_slots = new_ptr->h_next;
hp = hole_head;
/* If this block's address is numerically less than the lowest hole currently
* available, or if no holes are currently available, put this hole on the
* front of the hole list.
*/
if (hp == NIL_HOLE || base <= hp->h_base) {
/* Block to be freed goes on front of the hole list. */
new_ptr->h_next = hp;
hole_head = new_ptr;
merge(new_ptr);
return;
}
/* Block to be returned does not go on front of hole list. */
while (hp != NIL_HOLE && base > hp->h_base) {
prev_ptr = hp;
hp = hp->h_next;
}
/* We found where it goes. Insert block after 'prev_ptr'. */
new_ptr->h_next = prev_ptr->h_next;
prev_ptr->h_next = new_ptr;
merge(prev_ptr); /* sequence is 'prev_ptr', 'new_ptr', 'hp' */
}
/*===========================================================================*
* del_slot *
*===========================================================================*/
PRIVATE void del_slot(prev_ptr, hp)
register struct hole *prev_ptr; /* pointer to hole entry just ahead of 'hp' */
register struct hole *hp; /* pointer to hole entry to be removed */
{
/* Remove an entry from the hole list. This procedure is called when a
* request to allocate memory removes a hole in its entirety, thus reducing
* the numbers of holes in memory, and requiring the elimination of one
* entry in the hole list.
*/
if (hp == hole_head)
hole_head = hp->h_next;
else
prev_ptr->h_next = hp->h_next;
hp->h_next = free_slots;
free_slots = hp;
}
/*===========================================================================*
* merge *
*===========================================================================*/
PRIVATE void merge(hp)
register struct hole *hp; /* ptr to hole to merge with its successors */
{
/* Check for contiguous holes and merge any found. Contiguous holes can occur
* when a block of memory is freed, and it happens to abut another hole on
* either or both ends. The pointer 'hp' points to the first of a series of
* three holes that can potentially all be merged together.
*/
register struct hole *next_ptr;
/* If 'hp' points to the last hole, no merging is possible. If it does not,
* try to absorb its successor into it and free the successor's table entry.
*/
if ( (next_ptr = hp->h_next) == NIL_HOLE) return;
if (hp->h_base + hp->h_len == next_ptr->h_base) {
hp->h_len += next_ptr->h_len; /* first one gets second one's mem */
del_slot(hp, next_ptr);
} else {
hp = next_ptr;
}
/* If 'hp' now points to the last hole, return; otherwise, try to absorb its
* successor into it.
*/
if ( (next_ptr = hp->h_next) == NIL_HOLE) return;
if (hp->h_base + hp->h_len == next_ptr->h_base) {
hp->h_len += next_ptr->h_len;
del_slot(hp, next_ptr);
}
}
/*===========================================================================*
* mem_init *
*===========================================================================*/
PUBLIC void mem_init(total, free)
phys_clicks *total, *free; /* memory size summaries */
{
/* Initialize hole lists. There are two lists: 'hole_head' points to a linked
* list of all the holes (unused memory) in the system; 'free_slots' points to
* a linked list of table entries that are not in use. Initially, the former
* list has one entry for each chunk of physical memory, and the second
* list links together the remaining table slots. As memory becomes more
* fragmented in the course of time (i.e., the initial big holes break up into
* smaller holes), new table slots are needed to represent them. These slots
* are taken from the list headed by 'free_slots'.
*/
register struct hole *hp;
phys_clicks base; /* base address of chunk */
phys_clicks size; /* size of chunk */
message mess;
/* Put all holes on the free list. */
for (hp = &hole[0]; hp < &hole[NR_HOLES]; hp++) hp->h_next = hp + 1;
hole[NR_HOLES-1].h_next = NIL_HOLE;
hole_head = NIL_HOLE;
free_slots = &hole[0];
/* Ask the kernel for chunks of physical memory and allocate a hole for
* each of them. The SYS_MEM call responds with the base and size of the
* next chunk and the total amount of memory.
*/
*free = 0;
for (;;) {
mess.m_type = SYS_MEM;
if (sendrec(SYSTASK, &mess) != OK) panic("bad SYS_MEM?", NO_NUM);
base = mess.m1_i1;
size = mess.m1_i2;
if (size == 0) break; /* no more? */
free_mem(base, size);
*total = mess.m1_i3;
*free += size;
#if ENABLE_SWAP
if (swap_base < base + size) swap_base = base+size;
#endif
}
#if ENABLE_SWAP
/* The swap area is represented as a hole above and separate of regular
* memory. A hole at the size of the swap file is allocated on "swapon".
*/
swap_base++; /* make separate */
swap_maxsize = 0 - swap_base; /* maximum we can possibly use */
#endif
}
#if ENABLE_SWAP
/*===========================================================================*
* swap_on *
*===========================================================================*/
PUBLIC int swap_on(file, offset, size)
char *file; /* file to swap on */
u32_t offset, size; /* area on swap file to use */
{
/* Turn swapping on. */
if (swap_fd != -1) return(EBUSY); /* already have swap? */
tell_fs(CHDIR, who, FALSE, 0); /* be like the caller for open() */
if ((swap_fd = open(file, O_RDWR)) < 0) return(-errno);
swap_offset = offset;
size >>= CLICK_SHIFT;
if (size > swap_maxsize) size = swap_maxsize;
if (size > 0) free_mem(swap_base, (phys_clicks) size);
}
/*===========================================================================*
* swap_off *
*===========================================================================*/
PUBLIC int swap_off()
{
/* Turn swapping off. */
struct mproc *rmp;
struct hole *hp, *prev_ptr;
if (swap_fd == -1) return(OK); /* can't turn off what isn't on */
/* Put all swapped out processes on the inswap queue and swap in. */
for (rmp = &mproc[LOW_USER]; rmp < &mproc[NR_PROCS]; rmp++) {
if (rmp->mp_flags & ONSWAP) swap_inqueue(rmp);
}
swap_in();
/* All in memory? */
for (rmp = &mproc[LOW_USER]; rmp < &mproc[NR_PROCS]; rmp++) {
if (rmp->mp_flags & ONSWAP) return(ENOMEM);
}
/* Yes. Remove the swap hole and close the swap file descriptor. */
for (hp = hole_head; hp != NIL_HOLE; prev_ptr = hp, hp = hp->h_next) {
if (hp->h_base >= swap_base) {
del_slot(prev_ptr, hp);
hp = hole_head;
}
}
close(swap_fd);
swap_fd = -1;
return(OK);
}
/*===========================================================================*
* swap_inqueue *
*===========================================================================*/
PUBLIC void swap_inqueue(rmp)
register struct mproc *rmp; /* process to add to the queue */
{
/* Put a swapped out process on the queue of processes to be swapped in. This
* happens when such a process gets a signal, or if a reply message must be
* sent, like when a process doing a wait() has a child that exits.
*/
struct mproc **pmp;
if (rmp->mp_flags & SWAPIN) return; /* already queued */
for (pmp = &in_queue; *pmp != NULL; pmp = &(*pmp)->mp_swapq) {}
*pmp = rmp;
rmp->mp_swapq = NULL;
rmp->mp_flags |= SWAPIN;
}
/*===========================================================================*
* swap_in *
*===========================================================================*/
PUBLIC void swap_in()
{
/* Try to swap in a process on the inswap queue. We want to send it a message,
* interrupt it, or something.
*/
struct mproc **pmp, *rmp;
phys_clicks old_base, new_base, size;
off_t off;
int proc_nr;
pmp = &in_queue;
while ((rmp = *pmp) != NULL) {
proc_nr = (rmp - mproc);
size = rmp->mp_seg[S].mem_vir + rmp->mp_seg[S].mem_len
- rmp->mp_seg[D].mem_vir;
if (!(rmp->mp_flags & SWAPIN)) {
/* Guess it got killed. (Queue is cleaned here.) */
*pmp = rmp->mp_swapq;
continue;
} else
if ((new_base = alloc_mem(size)) == NO_MEM) {
/* No memory for this one, try the next. */
pmp = &rmp->mp_swapq;
} else {
/* We've found memory. Update map and swap in. */
old_base = rmp->mp_seg[D].mem_phys;
rmp->mp_seg[D].mem_phys = new_base;
rmp->mp_seg[S].mem_phys = rmp->mp_seg[D].mem_phys +
(rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
sys_newmap(proc_nr, rmp->mp_seg);
off = swap_offset + ((off_t) (old_base-swap_base)<<CLICK_SHIFT);
lseek(swap_fd, off, SEEK_SET);
rw_seg(0, swap_fd, proc_nr, D, (phys_bytes)size << CLICK_SHIFT);
free_mem(old_base, size);
rmp->mp_flags &= ~(ONSWAP|SWAPIN);
*pmp = rmp->mp_swapq;
check_pending(rmp); /* a signal may have waked this one */
}
}
}
/*===========================================================================*
* swap_out *
*===========================================================================*/
PRIVATE int swap_out()
{
/* Try to find a process that can be swapped out. Candidates are those blocked
* on a system call that MM handles, like wait(), pause() or sigsuspend().
*/
struct mproc *rmp;
struct hole *hp, *prev_ptr;
phys_clicks old_base, new_base, size;
off_t off;
int proc_nr;
rmp = outswap;
do {
if (++rmp == &mproc[NR_PROCS]) rmp = &mproc[LOW_USER];
/* A candidate? */
if (!(rmp->mp_flags & (PAUSED | WAITING | SIGSUSPENDED))) continue;
/* Already on swap or otherwise to be avoided? */
if (rmp->mp_flags & (TRACED | REPLY | ONSWAP)) continue;
/* Got one, find a swap hole and swap it out. */
proc_nr = (rmp - mproc);
size = rmp->mp_seg[S].mem_vir + rmp->mp_seg[S].mem_len
- rmp->mp_seg[D].mem_vir;
prev_ptr = NIL_HOLE;
for (hp = hole_head; hp != NIL_HOLE; prev_ptr = hp, hp = hp->h_next) {
if (hp->h_base >= swap_base && hp->h_len >= size) break;
}
if (hp == NIL_HOLE) continue; /* oops, not enough swapspace */
new_base = hp->h_base;
hp->h_base += size;
hp->h_len -= size;
if (hp->h_len == 0) del_slot(prev_ptr, hp);
off = swap_offset + ((off_t) (new_base - swap_base) << CLICK_SHIFT);
lseek(swap_fd, off, SEEK_SET);
rw_seg(1, swap_fd, proc_nr, D, (phys_bytes)size << CLICK_SHIFT);
old_base = rmp->mp_seg[D].mem_phys;
rmp->mp_seg[D].mem_phys = new_base;
rmp->mp_seg[S].mem_phys = rmp->mp_seg[D].mem_phys +
(rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
sys_newmap(proc_nr, rmp->mp_seg);
free_mem(old_base, size);
rmp->mp_flags |= ONSWAP;
outswap = rmp; /* next time start here */
return(TRUE);
} while (rmp != outswap);
return(FALSE); /* no candidate found */
}
#endif /* SWAP */

复制代码

zj21cn · 发表于 2008-7-10 09:03:40

linux的灵活性很强
不同的人有不同的配置
不同的机子也有不同的配置

一是提高充分挖掘机子的潜能，做到最合理的运用
二是满足不同层次的人在使用linux时有用不同的效果，满足不同需求

zbw76 · 发表于 2008-7-10 10:03:45

你们都没有理解楼主的意思啊，楼主心理想的是linux不够智能。

zj21cn · 发表于 2008-7-10 11:25:53

呵呵，大家都明白楼主的意思，反着说

一下子想起《大头儿子小头爸爸》动画片上的“喂饭机"
真智能

linuxahah · 发表于 2008-7-11 21:57:05

哇赛，竟有人敢在Linux论坛里说Linux灵活性太差.....
佩服...

zbw76 · 发表于 2008-7-12 12:19:34

Post by linuxahah;1873586
哇赛，竟有人敢在Linux论坛里说Linux灵活性太差.....
佩服...

哈哈,经典!!!

LinuxIsHard · 发表于 2008-7-12 12:51:28

stop, ok?
BTW, 换了主板不重装好像在windows也很麻烦啊....

zbw76 · 发表于 2008-7-12 22:59:32

Post by LinuxIsHard;1873730
stop, ok?
BTW, 换了主板不重装好像在windows也很麻烦啊....

哈哈,stop

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