diff options
Diffstat (limited to 'gdb/dcache.c')
| -rw-r--r-- | gdb/dcache.c | 560 |
1 files changed, 443 insertions, 117 deletions
diff --git a/gdb/dcache.c b/gdb/dcache.c index 722f731..61e4ed0 100644 --- a/gdb/dcache.c +++ b/gdb/dcache.c @@ -1,65 +1,191 @@ /* Caching code. Typically used by remote back ends for caching remote memory. - Copyright 1992, 1993 Free Software Foundation, Inc. + Copyright 1992, 1993, 1995 Free Software Foundation, Inc. -This file is part of GDB. + This file is part of GDB. -This program is free software; you can redistribute it and/or modify -it under the terms of the GNU General Public License as published by -the Free Software Foundation; either version 2 of the License, or -(at your option) any later version. + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. -This program is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. -You should have received a copy of the GNU General Public License -along with this program; if not, write to the Free Software -Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include "defs.h" #include "dcache.h" #include "gdbcmd.h" +#include <string.h> -int remote_dcache = 0; -/* In case the system header files define a prototype for insque and - remque that uses a pointer to a struct qelem, silence the warnings */ -#define Insque(a,b) insque((PTR)(a), (PTR)(b)) -#define Remque(a) remque((PTR)(a)) +/* + The data cache could lead to incorrect results because it doesn't know + about volatile variables, thus making it impossible to debug + functions which use memory mapped I/O devices. -/* The data cache records all the data read from the remote machine - since the last time it stopped. + set remotecache 0 - Each cache block holds LINE_SIZE bytes of data + In those cases. + + In general the dcache speeds up performance, some speed improvement + comes from the actual caching mechanism, but the major gain is in + the reduction of the remote protocol overhead; instead of reading + or writing a large area of memory in 4 byte requests, the cache + bundles up the requests into 32 byte (actually LINE_SIZE) chunks. + Reducing the overhead to an eighth of what it was. This is very + obvious when displaying a large amount of data, + + eg, x/200x 0 + + caching | no yes + ---------------------------- + first time | 4 sec 2 sec improvement due to chunking + second time | 4 sec 0 sec improvement due to caching + + The cache structure is unusual, we keep a number of cache blocks + (DCACHE_SIZE) and each one caches a LINE_SIZEed area of memory. + Within each line we remember the address of the line (always a + multiple of the LINE_SIZE) and a vector of bytes over the range. + There's another vector which contains the state of the bytes. + + ENTRY_BAD means that the byte is just plain wrong, and has no + correspondence with anything else (as it would when the cache is + turned on, but nothing has been done to it. + + ENTRY_DIRTY means that the byte has some data in it which should be + written out to the remote target one day, but contains correct + data. ENTRY_OK means that the data is the same in the cache as it + is in remote memory. + + + The ENTRY_DIRTY state is necessary because GDB likes to write large + lumps of memory in small bits. If the caching mechanism didn't + maintain the DIRTY information, then something like a two byte + write would mean that the entire cache line would have to be read, + the two bytes modified and then written out again. The alternative + would be to not read in the cache line in the first place, and just + write the two bytes directly into target memory. The trouble with + that is that it really nails performance, because of the remote + protocol overhead. This way, all those little writes are bundled + up into an entire cache line write in one go, without having to + read the cache line in the first place. + + + */ + + +/* This value regulates the number of cache blocks stored. + Smaller values reduce the time spent searching for a cache + line, and reduce memory requirements, but increase the risk + of a line not being in memory */ + +#define DCACHE_SIZE 64 + +/* This value regulates the size of a cache line. Smaller values + reduce the time taken to read a single byte, but reduce overall + throughput. */ + +#define LINE_SIZE_POWER (5) +#define LINE_SIZE (1 << LINE_SIZE_POWER) + +/* Each cache block holds LINE_SIZE bytes of data starting at a multiple-of-LINE_SIZE address. */ -#define LINE_SIZE_MASK ((LINE_SIZE - 1)) /* eg 7*2+1= 111*/ -#define XFORM(x) (((x) & LINE_SIZE_MASK) >> 2) +#define LINE_SIZE_MASK ((LINE_SIZE - 1)) +#define XFORM(x) ((x) & LINE_SIZE_MASK) +#define MASK(x) ((x) & ~LINE_SIZE_MASK) + + +#define ENTRY_BAD 0 /* data at this byte is wrong */ +#define ENTRY_DIRTY 1 /* data at this byte needs to be written back */ +#define ENTRY_OK 2 /* data at this byte is same as in memory */ + + +struct dcache_block +{ + struct dcache_block *p; /* next in list */ + unsigned int addr; /* Address for which data is recorded. */ + unsigned char data[LINE_SIZE]; /* bytes at given address */ + unsigned char state[LINE_SIZE]; /* what state the data is in */ + + /* whether anything in state is dirty - used to speed up the + dirty scan. */ + int anydirty; + + int refs; +}; + + +struct dcache_struct +{ + /* Function to actually read the target memory. */ + memxferfunc read_memory; + + /* Function to actually write the target memory */ + memxferfunc write_memory; + + /* free list */ + struct dcache_block *free_head; + struct dcache_block *free_tail; + + /* in use list */ + struct dcache_block *valid_head; + struct dcache_block *valid_tail; + + /* The cache itself. */ + struct dcache_block *the_cache; + + /* potentially, if the cache was enabled, and then turned off, and + then turned on again, the stuff in it could be stale, so this is + used to mark it */ + int cache_has_stuff; +} ; + +int remote_dcache = 1; + +DCACHE *last_cache; /* Used by info dcache */ + + /* Free all the data cache blocks, thus discarding all cached data. */ + void dcache_flush (dcache) DCACHE *dcache; { - register struct dcache_block *db; + int i; + dcache->valid_head = 0; + dcache->valid_tail = 0; + + dcache->free_head = 0; + dcache->free_tail = 0; + + for (i = 0; i < DCACHE_SIZE; i++) + { + struct dcache_block *db = dcache->the_cache + i; + + if (!dcache->free_head) + dcache->free_head = db; + else + dcache->free_tail->p = db; + dcache->free_tail = db; + db->p = 0; + } - if (remote_dcache > 0) - while ((db = dcache->dcache_valid.next) != &dcache->dcache_valid) - { - Remque (db); - Insque (db, &dcache->dcache_free); - } + dcache->cache_has_stuff = 0; return; } -/* - * If addr is present in the dcache, return the address of the block - * containing it. - */ +/* If addr is present in the dcache, return the address of the block + containing it. */ static struct dcache_block * dcache_hit (dcache, addr) @@ -68,35 +194,66 @@ dcache_hit (dcache, addr) { register struct dcache_block *db; - if (addr & 3 - || remote_dcache == 0) - abort (); - /* Search all cache blocks for one that is at this address. */ - db = dcache->dcache_valid.next; - while (db != &dcache->dcache_valid) + db = dcache->valid_head; + + while (db) { - if ((addr & ~LINE_SIZE_MASK) == db->addr) - return db; - db = db->next; + if (MASK(addr) == db->addr) + { + db->refs++; + return db; + } + db = db->p; } return NULL; } -/* Return the int data at address ADDR in dcache block DC. */ -static -int -dcache_value (db, addr) - struct dcache_block *db; - unsigned int addr; +/* Make sure that anything in this line which needs to + be written is. */ + +static int +dcache_write_line (dcache, db) + DCACHE *dcache; + register struct dcache_block *db; { - if (addr & 3 - || remote_dcache == 0) - abort (); - return (db->data[XFORM (addr)]); + int s; + int e; + s = 0; + if (db->anydirty) + { + for (s = 0; s < LINE_SIZE; s++) + { + if (db->state[s] == ENTRY_DIRTY) + { + int len = 0; + for (e = s ; e < LINE_SIZE; e++, len++) + if (db->state[e] != ENTRY_DIRTY) + { + /* all bytes from s..s+len-1 need to + be written out */ + int done = 0; + while (done < len) { + int t = dcache->write_memory (db->addr + s + done, + db->data + s + done, + len - done); + if (t == 0) + return 0; + done += t; + } + memset (db->state + s, ENTRY_OK, len); + s = e; + break; + } + } + } + db->anydirty = 0; + } + return 1; } + /* Get a free cache block, put or keep it on the valid list, and return its address. The caller should store into the block the address and data that it describes, then remque it from the @@ -112,116 +269,281 @@ dcache_alloc (dcache) register struct dcache_block *db; if (remote_dcache == 0) - abort(); + abort (); - if ((db = dcache->dcache_free.next) == &dcache->dcache_free) + /* Take something from the free list */ + if (db = dcache->free_head) { - /* If we can't get one from the free list, take last valid and put - it on the free list. */ - db = dcache->dcache_valid.last; - Remque (db); - Insque (db, &dcache->dcache_free); + dcache->free_head = db->p; + } + + if (!db) + { + /* Nothing left on free list, so grab on from the valid list */ + db = dcache->valid_head; + dcache->valid_head = db->p; + + dcache_write_line (dcache, db); } - Remque (db); - Insque (db, &dcache->dcache_valid); - return (db); + /* append this line to end of valid list */ + if (!dcache->valid_head) + dcache->valid_head = db; + else + dcache->valid_tail->p = db; + dcache->valid_tail = db; + db->p = 0; + + return db; } -/* Using the data cache DCACHE return the contents of the word at - address ADDR in the remote machine. */ +/* Using the data cache DCACHE return the contents of the byte at + address ADDR in the remote machine. + + Returns 0 on error. */ + int -dcache_fetch (dcache, addr) +dcache_peek_byte (dcache, addr, ptr) DCACHE *dcache; CORE_ADDR addr; + unsigned char *ptr; { - register struct dcache_block *db; - - if (remote_dcache == 0) - { - int i; - - (*dcache->read_memory) (addr, (unsigned char *) &i, 4); - return(i); - } - - db = dcache_hit (dcache, addr); - if (db == 0) + register struct dcache_block *db = dcache_hit (dcache, addr); + int ok=1; + int done = 0; + if (db == 0 + || db->state[XFORM (addr)] == ENTRY_BAD) { + if (db) + { + dcache_write_line (dcache, db); + } + else db = dcache_alloc (dcache); immediate_quit++; - (*dcache->read_memory) (addr & ~LINE_SIZE_MASK, (unsigned char *) db->data, LINE_SIZE); + db->addr = MASK (addr); + while (done < LINE_SIZE) + { + int try = + (*dcache->read_memory) + (db->addr + done, + (unsigned char *) db->data + done, + LINE_SIZE - done); + if (try == 0) + return 0; + done += try; + } immediate_quit--; - db->addr = addr & ~LINE_SIZE_MASK; - Remque (db); /* Off the free list */ - Insque (db, &dcache->dcache_valid); /* On the valid list */ + + memset (db->state, ENTRY_OK, sizeof (db->data)); + db->anydirty = 0; } - return (dcache_value (db, addr)); + *ptr = db->data[XFORM (addr)]; + return ok; } -/* Write the word at ADDR both in the data cache and in the remote machine. */ -void -dcache_poke (dcache, addr, data) +/* Using the data cache DCACHE return the contents of the word at + address ADDR in the remote machine. + + Returns 0 on error. */ + +int +dcache_peek (dcache, addr, data) DCACHE *dcache; CORE_ADDR addr; - int data; + int *data; { - register struct dcache_block *db; + unsigned char *dp = (unsigned char *) data; + int i; + for (i = 0; i < sizeof (int); i++) + { + if (!dcache_peek_byte (dcache, addr, dp + i)) + return 0; + } + return 1; +} - if (remote_dcache == 0) + +/* Writeback any dirty lines to the remote. */ +static int +dcache_writeback (dcache) + DCACHE *dcache; +{ + struct dcache_block *db; + + db = dcache->valid_head; + + while (db) { - (*dcache->write_memory) (addr, (unsigned char *) &data, 4); - return; + if (!dcache_write_line (dcache, db)) + return 0; + db = db->p; } + return 1; +} - /* First make sure the word is IN the cache. DB is its cache block. */ - db = dcache_hit (dcache, addr); - if (db == 0) + +/* Using the data cache DCACHE return the contents of the word at + address ADDR in the remote machine. */ +int +dcache_fetch (dcache, addr) + DCACHE *dcache; + CORE_ADDR addr; +{ + int res; + dcache_peek (dcache, addr, &res); + return res; +} + + +/* Write the byte at PTR into ADDR in the data cache. + Return zero on write error. + */ + +int +dcache_poke_byte (dcache, addr, ptr) + DCACHE *dcache; + CORE_ADDR addr; + char *ptr; +{ + register struct dcache_block *db = dcache_hit (dcache, addr); + + if (!db) { db = dcache_alloc (dcache); - immediate_quit++; - (*dcache->write_memory) (addr & ~LINE_SIZE_MASK, (unsigned char *) db->data, LINE_SIZE); - immediate_quit--; - db->addr = addr & ~LINE_SIZE_MASK; - Remque (db); /* Off the free list */ - Insque (db, &dcache->dcache_valid); /* On the valid list */ + db->addr = MASK (addr); + memset (db->state, ENTRY_BAD, sizeof (db->data)); } - /* Modify the word in the cache. */ - db->data[XFORM (addr)] = data; + db->data[XFORM (addr)] = *ptr; + db->state[XFORM (addr)] = ENTRY_DIRTY; + db->anydirty = 1; + return 1; +} - /* Send the changed word. */ - immediate_quit++; - (*dcache->write_memory) (addr, (unsigned char *) &data, 4); - immediate_quit--; +/* Write the word at ADDR both in the data cache and in the remote machine. + Return zero on write error. + */ + +int +dcache_poke (dcache, addr, data) + DCACHE *dcache; + CORE_ADDR addr; + int data; +{ + unsigned char *dp = (unsigned char *) (&data); + int i; + for (i = 0; i < sizeof (int); i++) + { + if (!dcache_poke_byte (dcache, addr, dp + i)) + return 0; + } + dcache_writeback (dcache); + return 1; } + /* Initialize the data cache. */ DCACHE * dcache_init (reading, writing) memxferfunc reading; memxferfunc writing; { - register i; - register struct dcache_block *db; + int csize = sizeof (struct dcache_block) * DCACHE_SIZE; DCACHE *dcache; dcache = (DCACHE *) xmalloc (sizeof (*dcache)); dcache->read_memory = reading; dcache->write_memory = writing; - dcache->the_cache = (struct dcache_block *) - xmalloc (sizeof (*dcache->the_cache) * DCACHE_SIZE); - dcache->dcache_free.next = dcache->dcache_free.last = &dcache->dcache_free; - dcache->dcache_valid.next = dcache->dcache_valid.last = &dcache->dcache_valid; - for (db = dcache->the_cache, i = 0; i < DCACHE_SIZE; i++, db++) - Insque (db, &dcache->dcache_free); + dcache->the_cache = (struct dcache_block *) xmalloc (csize); + memset (dcache->the_cache, 0, csize); + + dcache_flush (dcache); + + last_cache = dcache; + return dcache; +} + +/* Read or write LEN bytes from inferior memory at MEMADDR, transferring + to or from debugger address MYADDR. Write to inferior if SHOULD_WRITE is + nonzero. + + Returns length of data written or read; 0 for error. + + This routine is indended to be called by remote_xfer_ functions. */ + +int +dcache_xfer_memory (dcache, memaddr, myaddr, len, should_write) + DCACHE *dcache; + CORE_ADDR memaddr; + char *myaddr; + int len; + int should_write; +{ + int i; + + if (remote_dcache) + { + int (*xfunc) () + = should_write ? dcache_poke_byte : dcache_peek_byte; + + for (i = 0; i < len; i++) + { + if (!xfunc (dcache, memaddr + i, myaddr + i)) + return 0; + } + dcache->cache_has_stuff = 1; + dcache_writeback (dcache); + } + else + { + int (*xfunc) () + = should_write ? dcache->write_memory : dcache->read_memory; + + if (dcache->cache_has_stuff) + dcache_flush (dcache); - return(dcache); + len = xfunc (memaddr, myaddr, len); + } + return len; +} + +static void +dcache_info (exp, tty) + char *exp; + int tty; +{ + struct dcache_block *p; + + if (!remote_dcache) + { + printf_filtered ("Dcache not enabled\n"); + return; + } + printf_filtered ("Dcache enabled, line width %d, depth %d\n", + LINE_SIZE, DCACHE_SIZE); + + printf_filtered ("Cache state:\n"); + + for (p = last_cache->valid_head; p; p = p->p) + { + int j; + printf_filtered ("Line at %08xd, referenced %d times\n", + p->addr, p->refs); + + for (j = 0; j < LINE_SIZE; j++) + printf_filtered ("%02x", p->data[j]); + printf_filtered ("\n"); + + for (j = 0; j < LINE_SIZE; j++) + printf_filtered ("% 2x", p->state[j]); + printf_filtered ("\n"); + } } void -_initialitize_dcache () +_initialize_dcache () { add_show_from_set (add_set_cmd ("remotecache", class_support, var_boolean, @@ -232,7 +554,11 @@ When on, use data caching for remote targets. For many remote targets\n\ this option can offer better throughput for reading target memory.\n\ Unfortunately, gdb does not currently know anything about volatile\n\ registers and thus data caching will produce incorrect results with\n\ -volatile registers are in use. By default, this option is off.", +volatile registers are in use. By default, this option is on.", &setlist), &showlist); + + add_info ("dcache", dcache_info, + "Print information on the dcache performance."); + } |