9660srv: keep data and metadata separate in the cache with a tag

data on the disk is layed out sequentially and directory information
is at the end of the disk. we want to keep data and metadata separated
so that reading large sequential files will not evict the directory
information from the cache causing long seeks.

for that, we tag the clusters (an 8th for metadata, and the rest
for data) and getbuf() will only evict clusters of the same tag.

diff --git a/sys/src/cmd/9660srv/9660srv.c b/sys/src/cmd/9660srv/9660srv.c
index 37dbd444b51d6e01324a918f4fa45eaf72247dec..8fe773d1bd26e6f25f18a28a21de86c34df7ff3b 100644 (file)
--- a/sys/src/cmd/9660srv/9660srv.c
+++ b/sys/src/cmd/9660srv/9660srv.c
@@ -69,7 +69,7 @@ iattach(Xfile *root)
        dp = nil;
        haveplan9 = 0;
        for(i=VOLDESC;i<VOLDESC+100; i++){      /* +100 for sanity */
-               p = getbuf(cd->d, i);
+               p = getbuf(cd->d, i, 1);
                v = (Voldesc*)(p->iobuf);
                if(memcmp(v->byte, "\01CD001\01", 7) == 0){             /* iso */
                        if(dirp)
@@ -372,7 +372,7 @@ iread(Xfile *f, char *buf, vlong offset, long count)
        while(count > 0){
                if(n > count)
                        n = count;
-               p = getbuf(f->xf->d, addr);
+               p = getbuf(f->xf->d, addr, 0);
                memmove(&buf[rcnt], &p->iobuf[o], n);
                putbuf(p);
                count -= n;
@@ -499,7 +499,7 @@ getdrec(Xfile *f, void *buf)
                        ip->offset += Sectorsize-boff;
                        continue;
                }
-               p = getbuf(f->xf->d, addr/Sectorsize);
+               p = getbuf(f->xf->d, addr/Sectorsize, 1);
                len = p->iobuf[boff];
                if(len >= 34)
                        break;
@@ -754,7 +754,7 @@ getcontin(Xdata *dev, uchar *p, uchar **s)
        off = l32(p+12);
        len = l32(p+20);
        chat("getcontin %d...", bn);
-       b = getbuf(dev, bn);
+       b = getbuf(dev, bn, 1);
        if(b == 0){
                *s = 0;
                return 0;

diff --git a/sys/src/cmd/9660srv/dat.h b/sys/src/cmd/9660srv/dat.h
index bee14db6114889970a4ada7e100eca690c28b9e2..3949251a192b5b45cbd98e68f915d916e86fdb37 100644 (file)
--- a/sys/src/cmd/9660srv/dat.h
+++ b/sys/src/cmd/9660srv/dat.h
@@ -31,6 +31,7 @@ struct Ioclust
        int     nbuf;
        Iobuf*  buf;
        uchar*  iobuf;
+       ulong   tag;                    /* cache tag for eviction: 0 = data, 1 = metadata */
 };
 
 struct Xdata

diff --git a/sys/src/cmd/9660srv/fns.h b/sys/src/cmd/9660srv/fns.h
index 1bae3b507186c6a8fe61d58b28f265cf7b4483b6..2862d5a6384aaeff2fc66f2aaffbc90336414f33 100644 (file)
--- a/sys/src/cmd/9660srv/fns.h
+++ b/sys/src/cmd/9660srv/fns.h
@@ -1,7 +1,7 @@
 void   chat(char*, ...);
 void*  ealloc(long);
 void   error(char*);
-Iobuf* getbuf(Xdata*, ulong);
+Iobuf* getbuf(Xdata*, ulong, ulong);
 Xdata* getxdata(char*);
 void   iobuf_init(void);
 void   nexterror(void);

diff --git a/sys/src/cmd/9660srv/iobuf.c b/sys/src/cmd/9660srv/iobuf.c
index 6bba533e8fec6e3465f8597641a9d20346656ee4..a617483e61862976dfe4a0ef8e7f576558a56190 100644 (file)
--- a/sys/src/cmd/9660srv/iobuf.c
+++ b/sys/src/cmd/9660srv/iobuf.c
@@ -31,7 +31,7 @@ int nclust = NCLUST;
 static Ioclust*        iohead;
 static Ioclust*        iotail;
 
-static Ioclust*        getclust(Xdata*, long);
+static Ioclust*        getclust(Xdata*, long, ulong);
 static void    putclust(Ioclust*);
 static void    xread(Ioclust*);
 
@@ -53,6 +53,16 @@ iobuf_init(void)
        for(i=0; i<nclust; i++){
                c = (Ioclust*)mem;
                mem += sizeof(Ioclust);
+
+               /*
+                * on a iso filesystem, data is usually layed out sequentially
+                * but directory information is at the end of the disk. to avoid
+                * evicting directory information when reading large sequential
+                * files, we keep them tagged in the cache. for now, we use
+                * an 8th of the clusters for meta data.
+                */
+               c->tag = i <= (nclust/8);
+
                c->addr = -1;
                c->prev = iotail;
                if(iotail)
@@ -87,13 +97,13 @@ purgebuf(Xdata *dev)
 }
 
 static Ioclust*
-getclust(Xdata *dev, long addr)
+getclust(Xdata *dev, long addr, ulong tag)
 {
        Ioclust *c, *f;
 
        f = nil;
        for(c=iohead; c; c=c->next){
-               if(!c->busy)
+               if(!c->busy && c->tag == tag)
                        f = c;
                if(c->addr == addr && c->dev == dev){
                        c->busy++;
@@ -141,13 +151,13 @@ putclust(Ioclust *c)
 }
 
 Iobuf*
-getbuf(Xdata *dev, ulong addr)
+getbuf(Xdata *dev, ulong addr, ulong tag)
 {
        int off;
        Ioclust *c;
 
        off = addr%BUFPERCLUST;
-       c = getclust(dev, addr - off);
+       c = getclust(dev, addr - off, tag);
        if(c->nbuf < off){
                c->busy--;
                error("I/O read error");