shithub: gefs

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cache: fix cache discipline

Only blocks in the LRU list are candidates for
eviction from the cache. Since we need dirty
blocks to stay in the cache, they do not go into
the LRU list until they are synced.

	new -> cached|dirty -> cached|lru -> free

--- a/blk.c

+++ b/blk.c

@@ -76,7 +76,7 @@

 	vlong off, rem, n;

 	assert(bp != -1);

-	if((b = malloc(sizeof(Blk))) == nil)

+	if((b = blkbuf()) == nil)

 		return nil;

 	off = bp;

 	rem = Blksz;

@@ -291,6 +291,7 @@

 				putblk(pb);

 				return -1;

 			}

+			lrubump(pb);

 			putblk(pb);

 		}

 		*tl = lb;

@@ -438,7 +439,7 @@

 	PBIT64(p, (uvlong)LogEnd);

 	finalize(b);

 	if(syncblk(b) == -1){

-		free(b);

+		putblk(b);

 		return -1;

 	}

@@ -528,13 +529,11 @@

 			}

 			putblk(b);

 			lock(a);

-			lock(&fs->lrulk);

-			cachedel_lk(bp.addr);

+			cachedel(bp.addr);

 			if(blkdealloc_lk(ba) == -1){

 				unlock(a);

 				return -1;

 			}

-			unlock(&fs->lrulk);

 			unlock(a);

 		}

 	}

@@ -785,6 +784,7 @@

 	qlock(&fs->blklk[i]);

 	if((b = lookupblk(bp.addr)) != nil){

 		cacheblk(b);

+		lrubump(b);

 		qunlock(&fs->blklk[i]);

 		return b;

 	}

@@ -803,6 +803,7 @@

 	b->bp.hash = h;

 	b->bp.gen = bp.gen;

 	cacheblk(b);

+	lrubump(b);

 	qunlock(&fs->blklk[i]);

 	return b;

@@ -874,10 +875,8 @@

 	a = getarena(bp.addr);

 	lock(a);

-	lock(&fs->lrulk);

-	cachedel_lk(bp.addr);

+	cachedel(bp.addr);

 	blkdealloc_lk(bp.addr);

-	unlock(&fs->lrulk);

 	unlock(a);

 }

@@ -1034,6 +1033,7 @@

 				fprint(2, "write: %r");

 				abort();

 			}

+			lrubump(b);

 		}

 		putblk(b);

 	}

--- a/cache.c

+++ b/cache.c

@@ -6,7 +6,7 @@

 #include "dat.h"

 #include "fns.h"

-void

+static void

 cachedel_lk(vlong del)

 {

 	Bucket *bkt;

@@ -22,14 +22,12 @@

 			break;

 		p = &b->hnext;

 	}

-	if(b == nil){

-		unlock(bkt);

-		return;

-	}

-	*p = b->hnext;

 	unlock(bkt);

+	if(b == nil)

+		return;

+	assert(checkflag(b, Bcached));

-	assert(b != fs->chead || b != fs->ctail);

+	*p = b->hnext;

 	if(b->cnext != nil)

 		b->cnext->cprev = b->cprev;

 	if(b->cprev != nil)

@@ -40,17 +38,26 @@

 		fs->chead = b->cnext;

 	b->cnext = nil;

 	b->cprev = nil;

-	clrflag(b, Bcached);

 	fs->ccount--;

+

+	clrflag(b, Bcached);

 	putblk(b);

 }

+void

+cachedel(vlong del)

+{

+	lock(&fs->lrulk);

+	cachedel_lk(del);

+	unlock(&fs->lrulk);

+}

+

 Blk*

 cacheblk(Blk *b)

 {

 	Bucket *bkt;

-	Blk *e, *c;

 	u32int h;

+	Blk *e;

 	h = ihash(b->bp.addr);

 	bkt = &fs->cache[h % fs->cmax];

@@ -58,18 +65,33 @@

 	for(e = bkt->b; e != nil; e = e->hnext){

 		if(b == e)

 			goto Found;

-		if(b->bp.addr == e->bp.addr)

-			print("b: %p, e: %p\n", getmalloctag(b), getmalloctag(e));

 		assert(b->bp.addr != e->bp.addr);

 	}

 	b->hnext = bkt->b;

 	bkt->b = b;

+	if(!checkflag(b, Bcached)){

+		setflag(b, Bcached);

+		refblk(b);

+		fs->ccount++;

+	}

 Found:

 	unlock(bkt);

+	return b;

+}

+Blk*

+lrubump(Blk *b)

+{

+	Blk *c;

+

 	lock(&fs->lrulk);

+	if(checkflag(b, Bcached) == 0){

+		assert(b->cnext == nil);

+		assert(b->cprev == nil);

+		goto Done;

+	}

 	if(b == fs->chead)

-		goto Cached;

+		fs->chead = b->cnext;

 	if(b == fs->ctail)

 		fs->ctail = b->cprev;

@@ -84,15 +106,12 @@

 	b->cnext = fs->chead;

 	b->cprev = nil;

 	fs->chead = b;

-	if(!checkflag(b, Bcached)){

-		setflag(b, Bcached);

-		fs->ccount++;

-		refblk(b);

-	}

-	for(c = fs->ctail; c != nil && fs->ccount >= fs->cmax; c = fs->ctail)

+	for(c = fs->ctail; c != b && fs->ccount >= fs->cmax; c = fs->ctail){

+		assert(c != fs->chead);

 		cachedel_lk(c->bp.addr);

+	}

-Cached:

+Done:

 	unlock(&fs->lrulk);

 	return b;

 }

--- a/fns.h

+++ b/fns.h

@@ -17,7 +17,8 @@

 Blk*	getblk(Bptr, int);

 Blk*	refblk(Blk*);

 Blk*	cacheblk(Blk*);

-void	cachedel_lk(vlong);

+Blk*	lrubump(Blk*);

+void	cachedel(vlong);

 Blk*	lookupblk(vlong);

 Arena*	getarena(vlong);

 void	putblk(Blk*);

--- a/fs.c

+++ b/fs.c

@@ -2,6 +2,7 @@

 #include <libc.h>

 #include <auth.h>

 #include <fcall.h>

+#include <pool.h>

 #include <avl.h>

 #include "dat.h"