tventi: throw away dcache read-ahead code - plan9port - [fork] Plan 9 from user space
(HTM) git clone git://src.adamsgaard.dk/plan9port
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---
(DIR) commit 12c0e45f796863966ef7ab96b30df50a562ddb13
(DIR) parent b41e39aa1a726c08d5e9d5db55f2a4661aef2c42
(HTM) Author: Russ Cox <rsc@swtch.com>
Date: Mon, 24 Sep 2007 22:32:46 -0400
venti: throw away dcache read-ahead code
Diffstat:
M src/cmd/venti/srv/dcache.c | 181 +++++--------------------------
1 file changed, 27 insertions(+), 154 deletions(-)
---
(DIR) diff --git a/src/cmd/venti/srv/dcache.c b/src/cmd/venti/srv/dcache.c
t@@ -55,12 +55,6 @@ struct DCache
u8int *mem; /* memory for all block descriptors */
int ndirty; /* number of dirty blocks */
int maxdirty; /* max. number of dirty blocks */
- Channel *ra;
- u8int *rabuf;
- u32int ramax;
- u32int rasize;
- u64int raaddr;
- Part *rapart;
AState diskstate;
AState state;
t@@ -82,7 +76,6 @@ static void delheap(DBlock *db);
static void fixheap(int i, DBlock *b);
static void flushproc(void*);
static void writeproc(void*);
-static void raproc(void*);
void
initdcache(u32int mem)
t@@ -109,7 +102,6 @@ initdcache(u32int mem)
dcache.blocks = MKNZ(DBlock, nblocks);
dcache.write = MKNZ(DBlock*, nblocks);
dcache.mem = MKNZ(u8int, (nblocks+1+128) * blocksize);
- dcache.ra = chancreate(sizeof(Ra), 0);
last = nil;
p = (u8int*)(((ulong)dcache.mem+blocksize-1)&~(ulong)(blocksize-1));
t@@ -121,10 +113,6 @@ initdcache(u32int mem)
b->next = last;
last = b;
}
- dcache.rabuf = &p[i*blocksize];
- dcache.ramax = 128*blocksize;
- dcache.raaddr = 0;
- dcache.rapart = nil;
dcache.free = last;
dcache.nheap = 0;
t@@ -133,7 +121,6 @@ initdcache(u32int mem)
vtproc(flushproc, nil);
vtproc(delaykickroundproc, &dcache.round);
- vtproc(raproc, nil);
}
void
t@@ -156,115 +143,6 @@ diskstate(void)
return a;
}
-static void
-raproc(void *v)
-{
- Ra ra;
- DBlock *b;
-
- USED(v);
- while(recv(dcache.ra, &ra) == 1){
- if(ra.part->size <= ra.addr)
- continue;
- b = _getdblock(ra.part, ra.addr, OREAD, 2);
- putdblock(b);
- }
-}
-
-/*
- * We do readahead a whole arena at a time now,
- * so dreadahead is a no-op. The original implementation
- * is in unused_dreadahead below.
- */
-void
-dreadahead(Part *part, u64int addr, int miss)
-{
- USED(part);
- USED(addr);
- USED(miss);
-}
-
-void
-unused_dreadahead(Part *part, u64int addr, int miss)
-{
- Ra ra;
- static struct {
- Part *part;
- u64int addr;
- } lastmiss;
- static struct {
- Part *part;
- u64int addr;
- int dir;
- } lastra;
-
- if(miss){
- if(lastmiss.part==part && lastmiss.addr==addr-dcache.size){
- XRa:
- lastra.part = part;
- lastra.dir = addr-lastmiss.addr;
- lastra.addr = addr+lastra.dir;
- ra.part = part;
- ra.addr = lastra.addr;
- nbsend(dcache.ra, &ra);
- }else if(lastmiss.part==part && lastmiss.addr==addr+dcache.size){
- addr -= dcache.size;
- goto XRa;
- }
- }else{
- if(lastra.part==part && lastra.addr==addr){
- lastra.addr += lastra.dir;
- ra.part = part;
- ra.addr = lastra.addr;
- nbsend(dcache.ra, &ra);
- }
- }
-
- if(miss){
- lastmiss.part = part;
- lastmiss.addr = addr;
- }
-}
-
-int
-rareadpart(Part *part, u64int addr, u8int *buf, uint n, int load)
-{
- uint nn;
- static RWLock ralock;
-
- rlock(&ralock);
- if(dcache.rapart==part && dcache.raaddr <= addr && addr+n <= dcache.raaddr+dcache.rasize){
- memmove(buf, dcache.rabuf+(addr-dcache.raaddr), n);
- runlock(&ralock);
- return 0;
- }
- if(load != 2 || addr >= part->size){ /* addr >= part->size: let readpart do the error */
- runlock(&ralock);
- diskaccess(0);
- return readpart(part, addr, buf, n);
- }
-
- runlock(&ralock);
- wlock(&ralock);
-fprint(2, "raread %s %llx\n", part->name, addr);
- nn = dcache.ramax;
- if(addr+nn > part->size)
- nn = part->size - addr;
- diskaccess(0);
- if(readpart(part, addr, dcache.rabuf, nn) < 0){
- wunlock(&ralock);
- return -1;
- }
- memmove(buf, dcache.rabuf, n);
- dcache.rapart = part;
- dcache.rasize = nn;
- dcache.raaddr = addr;
- wunlock(&ralock);
-
- addstat(StatApartReadBytes, nn-n);
- return 0;
-}
-
static u32int
pbhash(u64int addr)
{
t@@ -313,16 +191,8 @@ _getdblock(Part *part, u64int addr, int mode, int load)
again:
for(b = dcache.heads[h]; b != nil; b = b->next){
if(b->part == part && b->addr == addr){
- /*
- qlock(&stats.lock);
- stats.pchit++;
- qunlock(&stats.lock);
- */
- if(load){
+ if(load)
addstat(StatDcacheHit, 1);
- if(load != 2 && mode != OWRITE)
- dreadahead(part, b->addr, 0);
- }
goto found;
}
}
t@@ -367,8 +237,6 @@ ZZZ this is not reasonable
b->addr = addr;
b->part = part;
b->size = 0;
- if(load != 2 && mode != OWRITE)
- dreadahead(part, b->addr, 1);
found:
b->ref++;
t@@ -377,6 +245,11 @@ found:
if(b->heap != TWID32)
fixheap(b->heap, b);
+ if((mode == ORDWR || mode == OWRITE) && part->writechan == nil){
+ trace(TraceBlock, "getdblock allocwriteproc %s", part->name);
+ part->writechan = chancreate(sizeof(DBlock*), dcache.nblocks);
+ vtproc(writeproc, part);
+ }
qunlock(&dcache.lock);
trace(TraceBlock, "getdblock lock");
t@@ -400,7 +273,8 @@ found:
memset(&b->data[b->size], 0, size - b->size);
else{
trace(TraceBlock, "getdblock readpart %s 0x%llux", part->name, addr);
- if(rareadpart(part, addr + b->size, &b->data[b->size], size - b->size, load) < 0){
+ diskaccess(0);
+ if(readpart(part, addr + b->size, &b->data[b->size], size - b->size) < 0){
b->mode = ORDWR; /* so putdblock wunlocks */
putdblock(b);
return nil;
t@@ -450,10 +324,9 @@ void
dirtydblock(DBlock *b, int dirty)
{
int odirty;
- Part *p;
-
- trace(TraceBlock, "dirtydblock enter %s 0x%llux %d from 0x%lux", b->part->name, b->addr, dirty, getcallerpc(&b));
+ trace(TraceBlock, "dirtydblock enter %s 0x%llux %d from 0x%lux",
+ b->part->name, b->addr, dirty, getcallerpc(&b));
assert(b->ref != 0);
assert(b->mode==ORDWR || b->mode==OWRITE);
t@@ -463,13 +336,6 @@ dirtydblock(DBlock *b, int dirty)
else
b->dirty = dirty;
- p = b->part;
- if(p->writechan == nil){
- trace(TraceBlock, "dirtydblock allocwriteproc %s", p->name);
- /* XXX hope this doesn't fail! */
- p->writechan = chancreate(sizeof(DBlock*), dcache.nblocks);
- vtproc(writeproc, p);
- }
qlock(&dcache.lock);
if(!odirty){
dcache.ndirty++;
t@@ -779,13 +645,13 @@ flushproc(void *v)
waitforkick(&dcache.round);
trace(TraceWork, "start");
+ t0 = nsec()/1000;
+ trace(TraceProc, "build t=%lud", (ulong)(nsec()/1000)-t0);
+
qlock(&dcache.lock);
as = dcache.state;
qunlock(&dcache.lock);
- t0 = nsec()/1000;
-
- trace(TraceProc, "build t=%lud", (ulong)(nsec()/1000)-t0);
write = dcache.write;
n = 0;
for(i=0; i<dcache.nblocks; i++){
t@@ -800,20 +666,26 @@ flushproc(void *v)
trace(TraceProc, "writeblocks t=%lud", (ulong)(nsec()/1000)-t0);
i = 0;
for(j=1; j<DirtyMax; j++){
- trace(TraceProc, "writeblocks.%d t=%lud", j, (ulong)(nsec()/1000)-t0);
+ trace(TraceProc, "writeblocks.%d t=%lud",
+ j, (ulong)(nsec()/1000)-t0);
i += parallelwrites(write+i, write+n, j);
}
if(i != n){
fprint(2, "in flushproc i=%d n=%d\n", i, n);
for(i=0; i<n; i++)
- fprint(2, "\tblock %d: dirty=%d\n", i, write[i]->dirty);
+ fprint(2, "\tblock %d: dirty=%d\n",
+ i, write[i]->dirty);
abort();
}
-/* XXX
-* the locking here is suspect. what if a block is redirtied
-* after the write happens? we'll still decrement dcache.ndirty here.
-*/
+ /*
+ * b->dirty is protected by b->lock while ndirty is protected
+ * by dcache.lock, so the --ndirty below is the delayed one
+ * from clearing b->dirty in the write proc. It may happen
+ * that some other proc has come along and redirtied b since
+ * the write. That's okay, it just means that ndirty may be
+ * one too high until we catch up and do the decrement.
+ */
trace(TraceProc, "undirty.%d t=%lud", j, (ulong)(nsec()/1000)-t0);
qlock(&dcache.lock);
dcache.diskstate = as;
t@@ -850,7 +722,8 @@ writeproc(void *v)
trace(TraceProc, "writepart %s 0x%llux", p->name, b->addr);
diskaccess(0);
if(writepart(p, b->addr, b->data, b->size) < 0)
- fprint(2, "write error: %r\n"); /* XXX details! */
+ fprint(2, "%s: writeproc: part %s addr 0x%llux: write error: %r\n",
+ argv0, p->name, b->addr);
addstat(StatApartWrite, 1);
addstat(StatApartWriteBytes, b->size);
b->dirty = 0;