return of venti

src/cmd/venti/srv/icache.c

@@ -0,0 +1,348 @@
+#include "stdinc.h"
+#include "dat.h"
+#include "fns.h"
+
+typedef struct ICache ICache;
+struct ICache
+{
+	QLock	lock;			/* locks hash table & all associated data */
+	Rendez	full;
+	IEntry	**heads;		/* heads of all the hash chains */
+	int	bits;			/* bits to use for indexing heads */
+	u32int	size;			/* number of heads; == 1 << bits, should be < entries */
+	IEntry	*base;			/* all allocated hash table entries */
+	u32int	entries;		/* elements in base */
+	IEntry	*dirty;		/* chain of dirty elements */
+	u32int	ndirty;
+	u32int	maxdirty;
+	u32int	unused;			/* index of first unused element in base */
+	u32int	stolen;			/* last head from which an element was stolen */
+
+	Arena	*last[4];
+	Arena	*lastload;
+	int		nlast;
+};
+
+static ICache icache;
+
+static IEntry	*icachealloc(IAddr *ia, u8int *score);
+
+/*
+ * bits is the number of bits in the icache hash table
+ * depth is the average depth
+ * memory usage is about (1<<bits) * depth * sizeof(IEntry) + (1<<bits) * sizeof(IEntry*)
+ */
+void
+initicache(int bits, int depth)
+{
+	icache.bits = bits;
+	icache.size = 1 << bits;
+	icache.entries = depth * icache.size;
+	icache.maxdirty = icache.entries/2;
+	icache.base = MKNZ(IEntry, icache.entries);
+	icache.heads = MKNZ(IEntry*, icache.size);
+	icache.full.l = &icache.lock;
+	setstat(StatIcacheSize, icache.entries);
+}
+
+u32int
+hashbits(u8int *sc, int bits)
+{
+	u32int v;
+
+	v = (sc[0] << 24) | (sc[1] << 16) | (sc[2] << 8) | sc[3];
+	if(bits < 32)
+		 v >>= (32 - bits);
+	return v;
+}
+
+static void
+loadarenaclumps(Arena *arena, u64int aa)
+{
+	ulong i;
+	ClumpInfo ci;
+	IAddr ia;
+
+fprint(2, "seed index cache with arena @%llud, (map %llud), %d clumps\n", arena->base, aa, arena->memstats.clumps);
+	for(i=0; i<arena->memstats.clumps; i++){
+		if(readclumpinfo(arena, i, &ci) < 0)
+			break;
+		ia.type = ci.type;
+		ia.size = ci.uncsize;
+		ia.blocks = (ci.size + ClumpSize + (1 << ABlockLog) - 1) >> ABlockLog;
+		ia.addr = aa;
+		aa += ClumpSize + ci.size;
+		if(ia.type != VtCorruptType)
+			insertscore(ci.score, &ia, 0);
+	}
+}
+
+/*
+ZZZ need to think about evicting the correct IEntry,
+and writing back the wtime.
+ * look up data score in the index cache
+ * if this fails, pull it in from the disk index table, if it exists.
+ *
+ * must be called with the lump for this score locked
+ */
+int
+lookupscore(u8int *score, int type, IAddr *ia, int *rac)
+{
+	IEntry d, *ie, *last;
+	u32int h;
+	u64int aa;
+	Arena *load;
+	int i;
+	uint ms;
+
+	load = nil;
+	aa = 0;
+	ms = msec();
+	
+	trace(TraceLump, "lookupscore %V.%d", score, type);
+
+	qlock(&icache.lock);
+	h = hashbits(score, icache.bits);
+	last = nil;
+	for(ie = icache.heads[h]; ie != nil; ie = ie->next){
+		if(ie->ia.type == type && scorecmp(ie->score, score)==0){
+			if(last != nil)
+				last->next = ie->next;
+			else
+				icache.heads[h] = ie->next;
+			addstat(StatIcacheHit, 1);
+			ie->rac = 1;
+			trace(TraceLump, "lookupscore incache");
+			goto found;
+		}
+		last = ie;
+	}
+	addstat(StatIcacheMiss, 1);
+	qunlock(&icache.lock);
+
+	if(loadientry(mainindex, score, type, &d) < 0){
+		ms = msec() - ms;
+		addstat2(StatIcacheRead, 1, StatIcacheReadTime, ms);
+		return -1;
+	}
+
+	addstat(StatIcacheFill, 1);
+
+	trace(TraceLump, "lookupscore loaded");
+
+	/*
+	 * no one else can load an entry for this score,
+	 * since we have the overall score lock.
+	 */
+	qlock(&icache.lock);
+
+	/*
+	 * If we notice that all the hits are coming from one arena,
+	 * load the table of contents for that arena into the cache.
+	 */
+	ie = icachealloc(&d.ia, score);
+	icache.last[icache.nlast++%nelem(icache.last)] = amapitoa(mainindex, ie->ia.addr, &aa);
+	aa = ie->ia.addr - aa;	/* compute base addr of arena */
+	for(i=0; i<nelem(icache.last); i++)
+		if(icache.last[i] != icache.last[0])
+			break;
+	if(i==nelem(icache.last) && icache.lastload != icache.last[0]){
+		load = icache.last[0];
+		icache.lastload = load;
+	}
+
+found:
+	ie->next = icache.heads[h];
+	icache.heads[h] = ie;
+
+	*ia = ie->ia;
+	*rac = ie->rac;
+
+	qunlock(&icache.lock);
+
+	if(load){
+		trace(TraceProc, "preload 0x%llux", aa);
+		loadarenaclumps(load, aa);
+	}
+	ms = msec() - ms;
+	addstat2(StatIcacheRead, 1, StatIcacheReadTime, ms);
+
+	return 0;
+}
+
+/*
+ * insert a new element in the hash table.
+ */
+int
+insertscore(u8int *score, IAddr *ia, int write)
+{
+	IEntry *ie, se;
+	u32int h;
+
+	trace(TraceLump, "insertscore enter");
+	if(write)
+		addstat(StatIcacheWrite, 1);
+	else
+		addstat(StatIcachePrefetch, 1);
+
+	qlock(&icache.lock);
+	h = hashbits(score, icache.bits);
+
+	ie = icachealloc(ia, score);
+	if(write){
+		icache.ndirty++;
+		setstat(StatIcacheDirty, icache.ndirty);
+		delaykickicache();
+		ie->dirty = 1;
+	}
+	ie->next = icache.heads[h];
+	icache.heads[h] = ie;
+
+	se = *ie;
+	qunlock(&icache.lock);
+
+	if(write && icache.ndirty >= icache.maxdirty)
+		kickicache();
+
+	/*
+	 * It's okay not to do this under icache.lock.
+	 * Calling insertscore only happens when we hold
+	 * the lump, meaning any searches for this block
+	 * will hit in the lump cache until after we return.
+	 */
+	markbloomfilter(mainindex->bloom, score);
+
+	return 0;
+}
+
+/*
+ * allocate a index cache entry which hasn't been used in a while.
+ * must be called with icache.lock locked
+ * if the score is already in the table, update the entry.
+ */
+static IEntry *
+icachealloc(IAddr *ia, u8int *score)
+{
+	int i;
+	IEntry *ie, *last, *clean, *lastclean;
+	u32int h;
+
+	h = hashbits(score, icache.bits);
+	last = nil;
+	for(ie = icache.heads[h]; ie != nil; ie = ie->next){
+		if(ie->ia.type == ia->type && scorecmp(ie->score, score)==0){
+			if(last != nil)
+				last->next = ie->next;
+			else
+				icache.heads[h] = ie->next;
+			trace(TraceLump, "icachealloc hit");
+			ie->rac = 1;
+			return ie;
+		}
+		last = ie;
+	}
+
+	h = icache.unused;
+	if(h < icache.entries){
+		ie = &icache.base[h++];
+		icache.unused = h;
+		trace(TraceLump, "icachealloc unused");
+		goto Found;
+	}
+
+	h = icache.stolen;
+	for(i=0;; i++){
+		h++;
+		if(h >= icache.size)
+			h = 0;
+		if(i == icache.size){
+			trace(TraceLump, "icachealloc sleep");
+			addstat(StatIcacheStall, 1);
+			while(icache.ndirty == icache.entries){
+				/*
+				 * This is a bit suspect.  Kickicache will wake up the
+				 * icachewritecoord, but if all the index entries are for
+				 * unflushed disk blocks, icachewritecoord won't be
+				 * able to do much.  It always rewakes everyone when
+				 * it thinks it is done, though, so at least we'll go around
+				 * the while loop again.  Also, if icachewritecoord sees
+				 * that the disk state hasn't change at all since the last
+				 * time around, it kicks the disk.  This needs to be
+				 * rethought, but it shouldn't deadlock anymore.
+				 */
+				kickicache();
+				rsleep(&icache.full);
+			}
+			addstat(StatIcacheStall, -1);
+			i = 0;
+		}
+		lastclean = nil;
+		clean = nil;
+		last = nil;
+		for(ie=icache.heads[h]; ie; last=ie, ie=ie->next){
+			if(!ie->dirty){
+				clean = ie;
+				lastclean = last;
+			}
+		}
+		if(clean){
+			if(lastclean)
+				lastclean->next = clean->next;
+			else
+				icache.heads[h] = clean->next;
+			clean->next = nil;
+			icache.stolen = h;
+			ie = clean;
+			trace(TraceLump, "icachealloc steal");
+			goto Found;
+		}
+	}
+
+Found:
+	ie->ia = *ia;
+	scorecp(ie->score, score);
+	ie->rac = 0;	
+	return ie;
+}
+
+IEntry*
+icachedirty(u32int lo, u32int hi, u64int limit)
+{
+	int i;
+	u32int h;
+	IEntry *ie, *dirty;
+
+	dirty = nil;
+	trace(TraceProc, "icachedirty enter");
+	qlock(&icache.lock);
+	for(i=0; i<icache.size; i++)
+	for(ie = icache.heads[i]; ie; ie=ie->next)
+		if(ie->dirty && ie->ia.addr != 0 && ie->ia.addr < limit){
+			h = hashbits(ie->score, 32);
+			if(lo <= h && h <= hi){
+				ie->nextdirty = dirty;
+				dirty = ie;
+			}
+		}
+	qunlock(&icache.lock);
+	trace(TraceProc, "icachedirty exit");
+	if(dirty == nil)
+		flushdcache();
+	return dirty;
+}
+
+void
+icacheclean(IEntry *ie)
+{
+	trace(TraceProc, "icachedirty enter");
+	qlock(&icache.lock);
+	for(; ie; ie=ie->nextdirty){
+		icache.ndirty--;
+		ie->dirty = 0;
+	}
+	setstat(StatIcacheDirty, icache.ndirty);
+	rwakeupall(&icache.full);
+	qunlock(&icache.lock);
+	trace(TraceProc, "icachedirty exit");
+}
+