1 78a779a3 2008-07-20 rsc #include <u.h>
  2 78a779a3 2008-07-20 rsc #include <libc.h>
  3 78a779a3 2008-07-20 rsc #include <auth.h>
  4 78a779a3 2008-07-20 rsc #include <fcall.h>
  5 78a779a3 2008-07-20 rsc #include "dat.h"
  6 78a779a3 2008-07-20 rsc #include "fns.h"
  7 78a779a3 2008-07-20 rsc 
  8 78a779a3 2008-07-20 rsc /*
  9 78a779a3 2008-07-20 rsc  * We used to use 100 i/o buffers of size 2kb (Sectorsize).
 10 78a779a3 2008-07-20 rsc  * Unfortunately, reading 2kb at a time often hopping around
 11 78a779a3 2008-07-20 rsc  * the disk doesn't let us get near the disk bandwidth.
 12 78a779a3 2008-07-20 rsc  *
 13 78a779a3 2008-07-20 rsc  * Based on a trace of iobuf address accesses taken while
 14 78a779a3 2008-07-20 rsc  * tarring up a Plan 9 distribution CD, we now use 16 128kb
 15 78a779a3 2008-07-20 rsc  * buffers.  This works for ISO9660 because data is required
 16 78a779a3 2008-07-20 rsc  * to be laid out contiguously; effectively we're doing agressive
 17 fa325e9b 2020-01-10 cross  * readahead.  Because the buffers are so big and the typical
 18 78a779a3 2008-07-20 rsc  * disk accesses so concentrated, it's okay that we have so few
 19 78a779a3 2008-07-20 rsc  * of them.
 20 78a779a3 2008-07-20 rsc  *
 21 78a779a3 2008-07-20 rsc  * If this is used to access multiple discs at once, it's not clear
 22 78a779a3 2008-07-20 rsc  * how gracefully the scheme degrades, but I'm not convinced
 23 78a779a3 2008-07-20 rsc  * it's worth worrying about.		-rsc
 24 78a779a3 2008-07-20 rsc  */
 25 78a779a3 2008-07-20 rsc 
 26 78a779a3 2008-07-20 rsc /* trying a larger value to get greater throughput - geoff */
 27 78a779a3 2008-07-20 rsc #define	BUFPERCLUST	256 /* sectors/cluster; was 64, 64*Sectorsize = 128kb */
 28 78a779a3 2008-07-20 rsc #define	NCLUST		16
 29 78a779a3 2008-07-20 rsc 
 30 78a779a3 2008-07-20 rsc int nclust = NCLUST;
 31 78a779a3 2008-07-20 rsc 
 32 78a779a3 2008-07-20 rsc static Ioclust*	iohead;
 33 78a779a3 2008-07-20 rsc static Ioclust*	iotail;
 34 78a779a3 2008-07-20 rsc 
 35 78a779a3 2008-07-20 rsc static Ioclust*	getclust(Xdata*, long);
 36 78a779a3 2008-07-20 rsc static void	putclust(Ioclust*);
 37 78a779a3 2008-07-20 rsc static void	xread(Ioclust*);
 38 78a779a3 2008-07-20 rsc 
 39 78a779a3 2008-07-20 rsc void
 40 78a779a3 2008-07-20 rsc iobuf_init(void)
 41 78a779a3 2008-07-20 rsc {
 42 78a779a3 2008-07-20 rsc 	int i, j, n;
 43 78a779a3 2008-07-20 rsc 	Ioclust *c;
 44 78a779a3 2008-07-20 rsc 	Iobuf *b;
 45 78a779a3 2008-07-20 rsc 	uchar *mem;
 46 78a779a3 2008-07-20 rsc 
 47 78a779a3 2008-07-20 rsc 	n = nclust*sizeof(Ioclust) +
 48 78a779a3 2008-07-20 rsc 		nclust*BUFPERCLUST*(sizeof(Iobuf)+Sectorsize);
 49 310ae033 2017-01-06 rsc 	mem = malloc(n);
 50 310ae033 2017-01-06 rsc 	if(mem == (void*)0)
 51 78a779a3 2008-07-20 rsc 		panic(0, "iobuf_init");
 52 78a779a3 2008-07-20 rsc 	memset(mem, 0, n);
 53 78a779a3 2008-07-20 rsc 
 54 78a779a3 2008-07-20 rsc 	for(i=0; i<nclust; i++){
 55 78a779a3 2008-07-20 rsc 		c = (Ioclust*)mem;
 56 78a779a3 2008-07-20 rsc 		mem += sizeof(Ioclust);
 57 78a779a3 2008-07-20 rsc 		c->addr = -1;
 58 78a779a3 2008-07-20 rsc 		c->prev = iotail;
 59 78a779a3 2008-07-20 rsc 		if(iotail)
 60 78a779a3 2008-07-20 rsc 			iotail->next = c;
 61 78a779a3 2008-07-20 rsc 		iotail = c;
 62 78a779a3 2008-07-20 rsc 		if(iohead == nil)
 63 78a779a3 2008-07-20 rsc 			iohead = c;
 64 78a779a3 2008-07-20 rsc 
 65 78a779a3 2008-07-20 rsc 		c->buf = (Iobuf*)mem;
 66 78a779a3 2008-07-20 rsc 		mem += BUFPERCLUST*sizeof(Iobuf);
 67 78a779a3 2008-07-20 rsc 		c->iobuf = mem;
 68 78a779a3 2008-07-20 rsc 		mem += BUFPERCLUST*Sectorsize;
 69 78a779a3 2008-07-20 rsc 		for(j=0; j<BUFPERCLUST; j++){
 70 78a779a3 2008-07-20 rsc 			b = &c->buf[j];
 71 78a779a3 2008-07-20 rsc 			b->clust = c;
 72 78a779a3 2008-07-20 rsc 			b->addr = -1;
 73 78a779a3 2008-07-20 rsc 			b->iobuf = c->iobuf+j*Sectorsize;
 74 78a779a3 2008-07-20 rsc 		}
 75 78a779a3 2008-07-20 rsc 	}
 76 78a779a3 2008-07-20 rsc }
 77 78a779a3 2008-07-20 rsc 
 78 78a779a3 2008-07-20 rsc void
 79 78a779a3 2008-07-20 rsc purgebuf(Xdata *dev)
 80 78a779a3 2008-07-20 rsc {
 81 78a779a3 2008-07-20 rsc 	Ioclust *p;
 82 78a779a3 2008-07-20 rsc 
 83 78a779a3 2008-07-20 rsc 	for(p=iohead; p!=nil; p=p->next)
 84 78a779a3 2008-07-20 rsc 		if(p->dev == dev){
 85 78a779a3 2008-07-20 rsc 			p->addr = -1;
 86 78a779a3 2008-07-20 rsc 			p->busy = 0;
 87 78a779a3 2008-07-20 rsc 		}
 88 78a779a3 2008-07-20 rsc }
 89 78a779a3 2008-07-20 rsc 
 90 78a779a3 2008-07-20 rsc static Ioclust*
 91 78a779a3 2008-07-20 rsc getclust(Xdata *dev, long addr)
 92 78a779a3 2008-07-20 rsc {
 93 78a779a3 2008-07-20 rsc 	Ioclust *c, *f;
 94 78a779a3 2008-07-20 rsc 
 95 78a779a3 2008-07-20 rsc 	f = nil;
 96 78a779a3 2008-07-20 rsc 	for(c=iohead; c; c=c->next){
 97 78a779a3 2008-07-20 rsc 		if(!c->busy)
 98 78a779a3 2008-07-20 rsc 			f = c;
 99 78a779a3 2008-07-20 rsc 		if(c->addr == addr && c->dev == dev){
100 78a779a3 2008-07-20 rsc 			c->busy++;
101 78a779a3 2008-07-20 rsc 			return c;
102 78a779a3 2008-07-20 rsc 		}
103 78a779a3 2008-07-20 rsc 	}
104 78a779a3 2008-07-20 rsc 
105 78a779a3 2008-07-20 rsc 	if(f == nil)
106 78a779a3 2008-07-20 rsc 		panic(0, "out of buffers");
107 78a779a3 2008-07-20 rsc 
108 78a779a3 2008-07-20 rsc 	f->addr = addr;
109 78a779a3 2008-07-20 rsc 	f->dev = dev;
110 78a779a3 2008-07-20 rsc 	f->busy++;
111 78a779a3 2008-07-20 rsc 	if(waserror()){
112 78a779a3 2008-07-20 rsc 		f->addr = -1;	/* stop caching */
113 78a779a3 2008-07-20 rsc 		putclust(f);
114 78a779a3 2008-07-20 rsc 		nexterror();
115 78a779a3 2008-07-20 rsc 	}
116 78a779a3 2008-07-20 rsc 	xread(f);
117 78a779a3 2008-07-20 rsc 	poperror();
118 78a779a3 2008-07-20 rsc 	return f;
119 78a779a3 2008-07-20 rsc }
120 78a779a3 2008-07-20 rsc 
121 78a779a3 2008-07-20 rsc static void
122 78a779a3 2008-07-20 rsc putclust(Ioclust *c)
123 78a779a3 2008-07-20 rsc {
124 78a779a3 2008-07-20 rsc 	if(c->busy <= 0)
125 78a779a3 2008-07-20 rsc 		panic(0, "putbuf");
126 78a779a3 2008-07-20 rsc 	c->busy--;
127 78a779a3 2008-07-20 rsc 
128 78a779a3 2008-07-20 rsc 	/* Link onto head for LRU */
129 78a779a3 2008-07-20 rsc 	if(c == iohead)
130 78a779a3 2008-07-20 rsc 		return;
131 78a779a3 2008-07-20 rsc 	c->prev->next = c->next;
132 78a779a3 2008-07-20 rsc 
133 78a779a3 2008-07-20 rsc 	if(c->next)
134 78a779a3 2008-07-20 rsc 		c->next->prev = c->prev;
135 78a779a3 2008-07-20 rsc 	else
136 78a779a3 2008-07-20 rsc 		iotail = c->prev;
137 78a779a3 2008-07-20 rsc 
138 78a779a3 2008-07-20 rsc 	c->prev = nil;
139 78a779a3 2008-07-20 rsc 	c->next = iohead;
140 78a779a3 2008-07-20 rsc 	iohead->prev = c;
141 78a779a3 2008-07-20 rsc 	iohead = c;
142 78a779a3 2008-07-20 rsc }
143 78a779a3 2008-07-20 rsc 
144 78a779a3 2008-07-20 rsc Iobuf*
145 78a779a3 2008-07-20 rsc getbuf(Xdata *dev, ulong addr)
146 78a779a3 2008-07-20 rsc {
147 78a779a3 2008-07-20 rsc 	int off;
148 78a779a3 2008-07-20 rsc 	Ioclust *c;
149 78a779a3 2008-07-20 rsc 
150 78a779a3 2008-07-20 rsc 	off = addr%BUFPERCLUST;
151 78a779a3 2008-07-20 rsc 	c = getclust(dev, addr - off);
152 78a779a3 2008-07-20 rsc 	if(c->nbuf < off){
153 78a779a3 2008-07-20 rsc 		c->busy--;
154 78a779a3 2008-07-20 rsc 		error("I/O read error");
155 78a779a3 2008-07-20 rsc 	}
156 78a779a3 2008-07-20 rsc 	return &c->buf[off];
157 78a779a3 2008-07-20 rsc }
158 78a779a3 2008-07-20 rsc 
159 78a779a3 2008-07-20 rsc void
160 78a779a3 2008-07-20 rsc putbuf(Iobuf *b)
161 78a779a3 2008-07-20 rsc {
162 78a779a3 2008-07-20 rsc 	putclust(b->clust);
163 78a779a3 2008-07-20 rsc }
164 78a779a3 2008-07-20 rsc 
165 78a779a3 2008-07-20 rsc static void
166 78a779a3 2008-07-20 rsc xread(Ioclust *c)
167 78a779a3 2008-07-20 rsc {
168 78a779a3 2008-07-20 rsc 	int n;
169 78a779a3 2008-07-20 rsc 	Xdata *dev;
170 78a779a3 2008-07-20 rsc 
171 78a779a3 2008-07-20 rsc 	dev = c->dev;
172 78a779a3 2008-07-20 rsc 	seek(dev->dev, (vlong)c->addr * Sectorsize, 0);
173 78a779a3 2008-07-20 rsc 	n = readn(dev->dev, c->iobuf, BUFPERCLUST*Sectorsize);
174 78a779a3 2008-07-20 rsc 	if(n < Sectorsize)
175 78a779a3 2008-07-20 rsc 		error("I/O read error");
176 78a779a3 2008-07-20 rsc 	c->nbuf = n/Sectorsize;
177 78a779a3 2008-07-20 rsc }