uvm_readahead.c revision 1.1.2.4
1 /* $NetBSD: uvm_readahead.c,v 1.1.2.4 2005/11/15 11:32:01 yamt Exp $ */ 2 3 /*- 4 * Copyright (c)2003, 2005 YAMAMOTO Takashi, 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __KERNEL_RCSID(0, "$NetBSD: uvm_readahead.c,v 1.1.2.4 2005/11/15 11:32:01 yamt Exp $"); 31 32 #include <sys/param.h> 33 #include <sys/pool.h> 34 #include <sys/fcntl.h> /* POSIX_FADV_* */ 35 36 #include <uvm/uvm.h> 37 #include <uvm/uvm_readahead.h> 38 39 struct uvm_ractx { 40 int ra_flags; 41 #define RA_VALID 1 42 int ra_advice; 43 off_t ra_winstart; 44 size_t ra_winsize; 45 off_t ra_next; 46 }; 47 48 /* 49 * XXX tune 50 * XXX should consider the amount of memory in the system 51 */ 52 53 #define RA_WINSIZE_INIT MAXPHYS 54 #define RA_WINSIZE_MAX (MAXPHYS * 8) 55 #define RA_WINSIZE_SEQENTIAL RA_WINSIZE_MAX 56 #define RA_MINSIZE (MAXPHYS * 2) 57 58 static off_t ra_startio(struct uvm_object *, off_t, size_t); 59 static struct uvm_ractx *ra_allocctx(void); 60 static void ra_freectx(struct uvm_ractx *); 61 62 POOL_INIT(ractx_pool, sizeof(struct uvm_ractx), 0, 0, 0, "ractx", 63 &pool_allocator_nointr); 64 65 static struct uvm_ractx * 66 ra_allocctx(void) 67 { 68 69 return pool_get(&ractx_pool, PR_NOWAIT); 70 } 71 72 static void 73 ra_freectx(struct uvm_ractx *ra) 74 { 75 76 pool_put(&ractx_pool, ra); 77 } 78 79 static off_t 80 ra_startio(struct uvm_object *uobj, off_t off, size_t sz) 81 { 82 const off_t endoff = off + sz; 83 84 #if defined(READAHEAD_DEBUG) 85 printf("%s: uobj=%p, off=%" PRIu64 ", endoff=%" PRIu64 "\n", 86 __func__, uobj, off, endoff); 87 #endif /* defined(READAHEAD_DEBUG) */ 88 off = trunc_page(off); 89 while (off < endoff) { 90 const size_t chunksize = MAXPHYS; 91 int error; 92 size_t donebytes; 93 int npages; 94 int orignpages; 95 size_t bytelen; 96 97 KASSERT((chunksize & (chunksize - 1)) == 0); 98 KASSERT((off & PAGE_MASK) == 0); 99 bytelen = ((off + chunksize) & -(off_t)chunksize) - off; 100 #if defined(READAHEAD_DEBUG) 101 printf("%s: off=%" PRIu64 ", bytelen=%zu\n", 102 __func__, off, bytelen); 103 #endif /* defined(READAHEAD_DEBUG) */ 104 KASSERT((bytelen & PAGE_MASK) == 0); 105 npages = orignpages = bytelen >> PAGE_SHIFT; 106 KASSERT(npages != 0); 107 simple_lock(&uobj->vmobjlock); 108 error = (*uobj->pgops->pgo_get)(uobj, off, NULL, 109 &npages, 0, VM_PROT_READ, 0, 0); 110 if (error) { 111 #if defined(READAHEAD_DEBUG) 112 if (error != EINVAL) { 113 printf("%s: error=%d\n", __func__, error); 114 } 115 #endif /* defined(READAHEAD_DEBUG) */ 116 break; 117 } 118 KASSERT(orignpages == npages); 119 donebytes = orignpages << PAGE_SHIFT; 120 off += donebytes; 121 } 122 123 return off; 124 } 125 126 /* ------------------------------------------------------------ */ 127 128 struct uvm_ractx * 129 uvm_ra_allocctx(int advice) 130 { 131 struct uvm_ractx *ra; 132 133 KASSERT(advice == POSIX_FADV_NORMAL || 134 advice == POSIX_FADV_SEQUENTIAL || 135 advice == POSIX_FADV_RANDOM); 136 137 ra = ra_allocctx(); 138 if (ra != NULL) { 139 ra->ra_flags = 0; 140 ra->ra_winstart = 0; 141 ra->ra_advice = advice; 142 } 143 144 return ra; 145 } 146 147 void 148 uvm_ra_freectx(struct uvm_ractx *ra) 149 { 150 151 KASSERT(ra != NULL); 152 ra_freectx(ra); 153 } 154 155 void 156 uvm_ra_request(struct uvm_ractx *ra, struct uvm_object *uobj, 157 off_t reqoff, size_t reqsize) 158 { 159 160 if (ra == NULL) { 161 return; 162 } 163 164 switch (ra->ra_advice) { 165 case POSIX_FADV_NORMAL: 166 break; 167 168 case POSIX_FADV_RANDOM: 169 return; 170 171 case POSIX_FADV_SEQUENTIAL: 172 if (reqoff <= ra->ra_winstart) { 173 ra->ra_next = reqoff; 174 } 175 ra->ra_winsize = RA_WINSIZE_SEQENTIAL; 176 goto do_readahead; 177 178 default: 179 #if defined(DIAGNOSTIC) 180 panic("%s: unknown advice %d", __func__, ra->ra_advice); 181 #endif /* defined(DIAGNOSTIC) */ 182 break; 183 } 184 185 if ((ra->ra_flags & RA_VALID) == 0) { 186 initialize: 187 ra->ra_winstart = ra->ra_next = reqoff + reqsize; 188 ra->ra_winsize = RA_WINSIZE_INIT; 189 ra->ra_flags |= RA_VALID; 190 return; 191 } 192 193 if (reqoff < ra->ra_winstart || 194 ra->ra_winstart + ra->ra_winsize < reqoff) { 195 196 /* 197 * miss 198 */ 199 200 goto initialize; 201 } 202 203 /* 204 * hit 205 */ 206 207 do_readahead: 208 if (reqoff > ra->ra_next) { 209 ra->ra_next = reqoff; 210 } 211 212 if (reqoff + ra->ra_winsize > ra->ra_next) { 213 off_t raoff = MAX(reqoff, ra->ra_next); 214 size_t rasize = reqoff + ra->ra_winsize - ra->ra_next; 215 216 if (rasize >= RA_MINSIZE) { 217 ra->ra_next = ra_startio(uobj, raoff, rasize); 218 } 219 } 220 221 /* 222 * update window 223 */ 224 225 ra->ra_winstart = reqoff + reqsize; 226 ra->ra_winsize = MIN(RA_WINSIZE_MAX, ra->ra_winsize + reqsize); 227 } 228
Indexes created Thu Oct 02 14:10:14 GMT 2025