X-Git-Url: https://mattmccutchen.net/rsync/rsync-patches.git/blobdiff_plain/e1a060026ac0b80fb080dc17494a2036ad21397e..6e9495c76ccda5a38bb1fa68b19ff22e8c7a30ad:/dynamic_hash.diff

diff --git a/dynamic_hash.diff b/dynamic_hash.diff
index d5b7e56..af065c1 100644
--- a/dynamic_hash.diff
+++ b/dynamic_hash.diff
@@ -1,32 +1,44 @@
 This patch makes the processing of large really large files more efficient
 by making sure that the sender's hash table is large enough to hold all the
-checksum entries without being overloaded.  Unfortunately, the code adds a
-modulus calculation for (up to) every byte of the source file, which slows
-down the code for normal file sizes (e.g. 4 CPU seconds slower on a Pentium
-III when copying a 65 MB file without very much matching data).
+checksum entries without being overloaded.
 
-This was udapted for the latest codebase from a patch written by Shachar
+Updated to use the current hashtable method when possible, and the new
+hashtable method (which requires a modulus calculation for up to every byte
+of the source file) only on large files that need a larger hashtable size.
+This avoids slowing down files that don't need the extra-large hashtable.
+
+This was updated for the latest codebase from a patch written by Shachar
 Shemesh.
 
+To use this patch, run these commands for a successful build:
+
+    patch -p1 <patches/dynamic_hash.diff
+    ./configure                                 (optional if already run)
+    make
+
 --- old/match.c
 +++ new/match.c
-@@ -37,24 +37,31 @@ static int total_matches;
+@@ -39,40 +39,51 @@ static int total_matches;
  
  extern struct stats stats;
  
 -#define TABLESIZE (1<<16)
--
++#define TRADITIONAL_TABLESIZE (1<<16)
+ 
 +static uint32 tablesize;
  static int32 *hash_table;
  
--#define SUM2HASH2(s1,s2) (((s1) + (s2)) & 0xFFFF)
--#define SUM2HASH(sum) SUM2HASH2((sum)&0xFFFF,(sum)>>16)
-+#define SUM2HASH(sum) ((sum)%tablesize)
+ #define SUM2HASH2(s1,s2) (((s1) + (s2)) & 0xFFFF)
+ #define SUM2HASH(sum) SUM2HASH2((sum)&0xFFFF,(sum)>>16)
  
- static void build_hash_table(struct sum_struct *s)
+-static int32 build_hash_table(struct sum_struct *s, int32 start)
++#define BIG_SUM2HASH(sum) ((sum)%tablesize)
++
++static void build_hash_table(struct sum_struct *s)
  {
- 	int32 i;
-+	uint32 prior_size = tablesize;
+-	int32 i, end = s->count;
++	static uint32 alloc_size;
++	int32 i;
  
 -	if (!hash_table) {
 -		hash_table = new_array(int32, TABLESIZE);
@@ -34,32 +46,104 @@ Shemesh.
 +	 * for big files is about 80%.  This number must be odd or s2 will
 +	 * not be able to span the entire set. */
 +	tablesize = (uint32)(s->count/8) * 10 + 11;
-+	if (tablesize < 65537)
-+		tablesize = 65537; /* a prime number */
-+	if (tablesize != prior_size) {
++	if (tablesize < TRADITIONAL_TABLESIZE)
++		tablesize = TRADITIONAL_TABLESIZE;
++	if (tablesize > alloc_size || tablesize < alloc_size - 16*1024) {
 +		if (hash_table)
 +			free(hash_table);
 +		hash_table = new_array(int32, tablesize);
  		if (!hash_table)
  			out_of_memory("build_hash_table");
++		alloc_size = tablesize;
  	}
  
 -	memset(hash_table, 0xFF, TABLESIZE * sizeof hash_table[0]);
+-
+-	if (end - start > TABLESIZE*8/10)
+-		end = start + TABLESIZE*8/10;
+-
+-	for (i = start; i < end; i++) {
+-		uint32 t = SUM2HASH(s->sums[i].sum1);
+-		s->sums[i].chain = hash_table[t];
+-		hash_table[t] = i;
+-	}
 +	memset(hash_table, 0xFF, tablesize * sizeof hash_table[0]);
  
- 	for (i = 0; i < s->count; i++) {
- 		uint32 t = SUM2HASH(s->sums[i].sum1);
-@@ -162,11 +169,11 @@ static void hash_search(int f,struct sum
+-	if (verbose > 2) {
+-		rprintf(FINFO, "built hash table for entries %ld - %ld\n",
+-			(long)start, (long)end - 1);
++	if (tablesize == TRADITIONAL_TABLESIZE) {
++		for (i = 0; i < s->count; i++) {
++			uint32 t = SUM2HASH(s->sums[i].sum1);
++			s->sums[i].chain = hash_table[t];
++			hash_table[t] = i;
++		}
++	} else {
++		for (i = 0; i < s->count; i++) {
++			uint32 t = BIG_SUM2HASH(s->sums[i].sum1);
++			s->sums[i].chain = hash_table[t];
++			hash_table[t] = i;
++		}
+ 	}
+-
+-	return end;
+ }
+ 
+ 
+@@ -130,8 +141,8 @@ static void matched(int f, struct sum_st
+ static void hash_search(int f,struct sum_struct *s,
+ 			struct map_struct *buf, OFF_T len)
+ {
+-	OFF_T offset, end, reset = 0;
+-	int32 k, want_i, backup, sum_pos = 0;
++	OFF_T offset, end;
++	int32 k, want_i, backup;
+ 	char sum2[SUM_LENGTH];
+ 	uint32 s1, s2, sum;
+ 	int more;
+@@ -169,24 +180,21 @@ static void hash_search(int f,struct sum
+ 		int done_csum2 = 0;
+ 		int32 i;
+ 
+-		if (offset >= reset) {
+-			sum_pos = build_hash_table(s, sum_pos);
+-			if (sum_pos == s->count)
+-				reset = len;
+-			else
+-				reset = sum_pos * s->blength;
+-		}
+-
+ 		if (verbose > 4) {
+ 			rprintf(FINFO, "offset=%.0f sum=%04x%04x\n",
  				(double)offset, s2 & 0xFFFF, s1 & 0xFFFF);
  		}
  
 -		i = hash_table[SUM2HASH2(s1,s2)];
-+		sum = (s1 & 0xffff) | (s2 << 16);
-+		i = hash_table[SUM2HASH(sum)];
- 		if (i < 0)
- 			goto null_hash;
+-		if (i < 0)
+-			goto null_hash;
++		if (tablesize == TRADITIONAL_TABLESIZE) {
++			if ((i = hash_table[SUM2HASH2(s1,s2)]) < 0)
++				goto null_hash;
++			sum = (s1 & 0xffff) | (s2 << 16);
++		} else {
++			sum = (s1 & 0xffff) | (s2 << 16);
++			if ((i = hash_table[BIG_SUM2HASH(sum)]) < 0)
++				goto null_hash;
++		}
  
 -		sum = (s1 & 0xffff) | (s2 << 16);
  		hash_hits++;
  		do {
  			int32 l;
+@@ -354,6 +362,11 @@ void match_sums(int f, struct sum_struct
+ 	}
+ 
+ 	if (len > 0 && s->count > 0) {
++		build_hash_table(s);
++
++		if (verbose > 2)
++			rprintf(FINFO,"built hash table\n");
++
+ 		hash_search(f, s, buf, len);
+ 
+ 		if (verbose > 2)