From ee56fa4695e4e27ca03d543f2b91118584f3d049 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Fri, 6 Aug 1999 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1999-08-06

---
 mpc/devsac.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 mpc/main.c   |  2 +-
 port/tod.c   |  8 ++++----
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/mpc/devsac.c b/mpc/devsac.c
index 11a2e547d81961fd0bd1f10056e3516668a61993..10092996347378cb4e4eec14d178df120c4e7412 100644
--- a/mpc/devsac.c
+++ b/mpc/devsac.c
@@ -17,12 +17,14 @@ enum
 {
 	OPERM	= 0x3,		/* mask of all permission types in open mode */
 	Nram	= 512,
+	CacheSize = 20,
 };
 
 typedef struct SacPath SacPath;
 typedef struct Sac Sac;
 typedef struct SacHeader SacHeader;
 typedef struct SacDir SacDir;
+typedef struct Cache Cache;
 
 enum {
 	Magic = 0x5acf5,
@@ -64,6 +66,13 @@ struct SacPath
 	int entry;
 };
 
+struct Cache
+{
+	long block;
+	ulong age;
+	uchar *data;
+};
+
 enum
 {
 	Pexec =		1,
@@ -77,6 +86,8 @@ enum
 static uchar *data = SACMEM;
 static int blocksize;
 static Sac root;
+static Cache cache[CacheSize];
+static ulong cacheage;
 
 static void	sacdir(Chan *, SacDir*, char*);
 static ulong	getl(void *p);
@@ -91,6 +102,9 @@ static void
 sacinit(void)
 {
 	SacHeader *hdr;
+	uchar *p;
+	int i;
+
 print("sacinit\n");
 	hdr = (SacHeader*)data;
 	if(getl(hdr->magic) != Magic) {
@@ -99,6 +113,13 @@ print("devsac: bad magic\n");
 	}
 	blocksize = getl(hdr->blocksize);
 	root.SacDir = *(SacDir*)(data + sizeof(SacHeader));
+	p = malloc(CacheSize*blocksize);
+	if(p == nil)
+		error("allocating cache");
+	for(i=0; i<CacheSize; i++) {
+		cache[i].data = p;
+		p += blocksize;
+	}
 }
 
 static Chan*
@@ -310,16 +331,41 @@ static void
 loadblock(void *buf, uchar *offset, int blocksize)
 {
 	vlong block, n;
+	ulong age;
+	int i, j;
 
 	block = getv(offset);
 	if(block < 0) {
 		block = -block;
+		cacheage++;
+		// age has wraped
+		if(cacheage == 0) {
+			for(i=0; i<CacheSize; i++)
+				cache[i].age = 0;
+		}
+		j = 0;
+		age = cache[0].age;
+		for(i=0; i<CacheSize; i++) {
+			if(cache[i].age < age) {
+				age = cache[i].age;
+				j = i;
+			}
+			if(cache[i].block != block)
+				continue;
+			memmove(buf, cache[i].data, blocksize);
+			cache[i].age = cacheage;
+			return;
+		}
+
 		n = getv(offset+8);
 		if(n < 0)
 			n = -n;
 		n -= block;
 		if(unsac(buf, data+block, blocksize, n)<0)
 			panic("unsac failed!");
+		memmove(cache[j].data, buf, blocksize);
+		cache[j].age = cacheage;
+		cache[j].block = block;
 	} else {
 		memmove(buf, data+block, blocksize);
 	}
diff --git a/mpc/main.c b/mpc/main.c
index 0c331862327deafd5ca715e3d6ca21a2fc3fe7de..82efbc258b10d2a17f37021796377892b30c7b88 100644
--- a/mpc/main.c
+++ b/mpc/main.c
@@ -259,7 +259,7 @@ confinit(void)
 	ulong pa;
 
 	conf.nmach = 1;		/* processors */
-	conf.nproc = 30;	/* processes */
+	conf.nproc = 40;	/* processes */
 
 	// hard wire for now
 	pa = 0xffd00000;		// leave 1 Meg for kernel
diff --git a/port/tod.c b/port/tod.c
index 0b4536fffb527c1aa518a268872ef27b0b33531d..7cdf94134515bb86acb53bd54e9980806a904762 100644
--- a/port/tod.c
+++ b/port/tod.c
@@ -80,7 +80,7 @@ todset(vlong t, vlong delta, int n)
 			n = -delta;
 		if(delta > 0 && n > delta)
 			n = delta;
-		delta /= n;
+		delta = delta/n;
 		tod.sstart = MACHP(0)->ticks;
 		tod.send = tod.sstart + n;
 		tod.delta = delta;
@@ -111,13 +111,13 @@ todget(vlong *ticksp)
 		t = MACHP(0)->ticks;
 		if(t >= tod.send)
 			t = tod.send;
-		tod.off += tod.delta*(t - tod.sstart);
+		tod.off = tod.off + tod.delta*(t - tod.sstart);
 		tod.sstart = t;
 	}
 
 	// convert to epoch
 	x = (diff * tod.multiplier) >> 31;
-	x += tod.off;
+	x = x + tod.off;
 
 	// protect against overflows
 	if(diff > tod.hz){
@@ -159,7 +159,7 @@ seconds(void)
 	int i;
 
 	x = todget(nil);
-	x /= TODFREQ;
+	x = x/TODFREQ;
 	i = x;
 	return i;
 }