Implement ability to partition chunks at the last rabin boundary instead of fixed size.

main.c

@@ -78,6 +78,7 @@ static int nthreads = 0;
 static int hide_mem_stats = 1;
 static int hide_cmp_stats = 1;
 static int enable_rabin_scan = 0;
+static int enable_rabin_split = 1;
 static unsigned int chunk_num;
 static uint64_t largest_chunk, smallest_chunk, avg_chunk;
 static const char *exec_name;
@@ -116,6 +117,7 @@ usage(void)
 	    "   %s -p ...\n"
 	    "4) Attempt Rabin fingerprinting based deduplication on chunks:\n"
 	    "   %s -D ...\n"
+	    "   %s -D -r ... - Do NOT split chunks at a rabin boundary. Default is to split.\n"
 	    "5) Number of threads can optionally be specified: -t <1 - 256 count>\n"
 	    "6) Pass '-M' to display memory allocator statistics\n"
 	    "7) Pass '-C' to display compression statistics\n\n",
@@ -602,7 +604,7 @@ redo:
 		rbytes = tdat->rbytes;
 		reset_rabin_context(tdat->rctx);
 		rctx->cbuf = tdat->uncompressed_chunk;
-		rabin_index_sz = rabin_dedup(tdat->rctx, tdat->cmp_seg, &(tdat->rbytes), 0);
+		rabin_index_sz = rabin_dedup(tdat->rctx, tdat->cmp_seg, &(tdat->rbytes), 0, NULL);
 		if (!rctx->valid) {
 			memcpy(tdat->uncompressed_chunk, tdat->cmp_seg, rbytes);
 			tdat->rbytes = rbytes;
@@ -753,7 +755,7 @@ start_compress(const char *filename, uint64_t chunksize, int level)
 	char tmpfile1[MAXPATHLEN];
 	char to_filename[MAXPATHLEN];
 	ssize_t compressed_chunksize;
-	ssize_t n_chunksize, rbytes;
+	ssize_t n_chunksize, rbytes, rabin_count;
 	short version, flags;
 	struct stat sbuf;
 	int compfd = -1, uncompfd = -1, err;
@@ -762,6 +764,7 @@ start_compress(const char *filename, uint64_t chunksize, int level)
 	struct cmp_data **dary = NULL, *tdat;
 	pthread_t writer_thr;
 	uchar_t *cread_buf, *pos;
+	rabin_context_t *rctx;
 
 	/*
 	 * Compressed buffer size must include zlib scratch space and
@@ -956,11 +959,17 @@ start_compress(const char *filename, uint64_t chunksize, int level)
 	largest_chunk = 0;
 	smallest_chunk = chunksize;
 	avg_chunk = 0;
+	rabin_count = 0;
 
 	/*
 	 * Read the first chunk into a spare buffer (a simple double-buffering).
 	 */
-	rbytes = Read(uncompfd, cread_buf, chunksize);
+	if (enable_rabin_split) {
+		rctx = create_rabin_context(chunksize, 0, algo);
+		rbytes = Read_Adjusted(uncompfd, cread_buf, chunksize, &rabin_count, rctx);
+	} else {
+		rbytes = Read(uncompfd, cread_buf, chunksize);
+	}
 
 	while (!bail) {
 		uchar_t *tmp;
@@ -990,6 +999,18 @@ start_compress(const char *filename, uint64_t chunksize, int level)
 				tdat->cmp_seg = cread_buf;
 				cread_buf = tmp;
 				tdat->compressed_chunk = tdat->cmp_seg + sizeof (chunksize) + sizeof (uint64_t);
+
+				/*
+				 * If there is data after the last rabin boundary in the chunk, then
+				 * rabin_count will be non-zero. We carry over the data to the beginning
+				 * of the next chunk.
+				 */
+				if (rabin_count) {
+					memcpy(cread_buf,
+					    tdat->cmp_seg + rabin_count, rbytes - rabin_count);
+					tdat->rbytes = rabin_count;
+					rabin_count = rbytes - rabin_count;
+				}
 			} else {
 				tmp = tdat->uncompressed_chunk;
 				tdat->uncompressed_chunk = cread_buf;
@@ -1014,7 +1035,11 @@ start_compress(const char *filename, uint64_t chunksize, int level)
 			 * Read the next buffer we want to process while previous
 			 * buffer is in progress.
 			 */
-			rbytes = Read(uncompfd, cread_buf, chunksize);
+			if (enable_rabin_split) {
+				rbytes = Read_Adjusted(uncompfd, cread_buf, chunksize, &rabin_count, rctx);
+			} else {
+				rbytes = Read(uncompfd, cread_buf, chunksize);
+			}
 		}
 	}
 
@@ -1088,6 +1113,7 @@ comp_done:
 		}
 		slab_free(NULL, dary);
 	}
+	if (enable_rabin_split) destroy_rabin_context(rctx);
 	slab_free(NULL, cread_buf);
 	if (!pipe_mode) {
 		if (compfd != -1) close(compfd);
@@ -1177,7 +1203,7 @@ main(int argc, char *argv[])
 	level = 6;
 	slab_init();
 
-	while ((opt = getopt(argc, argv, "dc:s:l:pt:MCD")) != -1) {
+	while ((opt = getopt(argc, argv, "dc:s:l:pt:MCDr")) != -1) {
 		int ovr;
 
 		switch (opt) {
@@ -1233,6 +1259,10 @@ main(int argc, char *argv[])
 			enable_rabin_scan = 1;
 			break;
 
+		    case 'r':
+			enable_rabin_split = 0;
+			break;
+
 		    case '?':
 		    default:
 			usage();

rabin/rabin_polynomial.c

@@ -123,21 +123,27 @@ create_rabin_context(uint64_t chunksize, uint64_t real_chunksize, const char *al
 		return (NULL);
 	}
 	current_window_data = slab_alloc(NULL, RAB_POLYNOMIAL_WIN_SIZE);
-	ctx->blocks = (rabin_blockentry_t *)slab_alloc(NULL,
-		blknum * ctx->rabin_poly_min_block_size);
-	if(ctx == NULL || current_window_data == NULL || ctx->blocks == NULL) {
+	ctx->blocks = NULL;
+	if (real_chunksize > 0) {
+		ctx->blocks = (rabin_blockentry_t *)slab_alloc(NULL,
+			blknum * ctx->rabin_poly_min_block_size);
+	}
+	if(ctx == NULL || current_window_data == NULL || (ctx->blocks == NULL && real_chunksize > 0)) {
 		fprintf(stderr,
 		    "Could not allocate rabin polynomial context, out of memory\n");
 		destroy_rabin_context(ctx);
 		return (NULL);
 	}
 
-	lzma_init(&(ctx->lzma_data), &(ctx->level), chunksize);
-	if (!(ctx->lzma_data)) {
-		fprintf(stderr,
-		    "Could not allocate rabin polynomial context, out of memory\n");
-		destroy_rabin_context(ctx);
-		return (NULL);
+	ctx->lzma_data = NULL;
+	if (real_chunksize > 0) {
+		lzma_init(&(ctx->lzma_data), &(ctx->level), chunksize);
+		if (!(ctx->lzma_data)) {
+			fprintf(stderr,
+			    "Could not allocate rabin polynomial context, out of memory\n");
+			destroy_rabin_context(ctx);
+			return (NULL);
+		}
 	}
 	/*
 	 * We should compute the power for the window size.
@@ -198,7 +204,7 @@ cmpblks(const void *a, const void *b)
  * the rolling checksum and dedup blocks vary in size from 4K-128K.
  */
 uint32_t
-rabin_dedup(rabin_context_t *ctx, uchar_t *buf, ssize_t *size, ssize_t offset)
+rabin_dedup(rabin_context_t *ctx, uchar_t *buf, ssize_t *size, ssize_t offset, ssize_t *rabin_pos)
 {
 	ssize_t i, last_offset,j;
 	uint32_t blknum;
@@ -211,6 +217,14 @@ rabin_dedup(rabin_context_t *ctx, uchar_t *buf, ssize_t *size, ssize_t offset)
 	ctx->valid = 0;
 	ctx->cur_checksum = 0;
 
+	/* 
+	 * If rabin_pos is non-zero then we are being asked to scan for the last rabin boundary
+	 * in the chunk. We start scanning at chunk end - max rabin block size. We avoid doing
+	 * a full chunk scan.
+	 */
+	if (rabin_pos) {
+		offset = *size - RAB_POLYNOMIAL_MAX_BLOCK_SIZE;
+	}
 	if (*size < ctx->rabin_poly_avg_block_size) return;
 	for (i=offset; i<*size; i++) {
 		char cur_byte = buf1[i];
@@ -241,18 +255,24 @@ rabin_dedup(rabin_context_t *ctx, uchar_t *buf, ssize_t *size, ssize_t offset)
 		// If we hit our special value or reached the max block size update block offset
 		if ((ctx->cur_roll_checksum & ctx->rabin_avg_block_mask) == ctx->rabin_break_patt ||
 		    length >= rabin_polynomial_max_block_size) {
-			ctx->blocks[blknum].offset = last_offset;
-			ctx->blocks[blknum].index = blknum; // Need to store for sorting
-			ctx->blocks[blknum].cksum_n_offset = ctx->cur_checksum;
-			ctx->blocks[blknum].length = length;
-			ctx->blocks[blknum].refcount = 0;
-			blknum++;
+			if (rabin_pos == NULL) {
+				ctx->blocks[blknum].offset = last_offset;
+				ctx->blocks[blknum].index = blknum; // Need to store for sorting
+				ctx->blocks[blknum].cksum_n_offset = ctx->cur_checksum;
+				ctx->blocks[blknum].length = length;
+				ctx->blocks[blknum].refcount = 0;
+				blknum++;
+			}
 			ctx->cur_checksum = 0;
 			last_offset = i+1;
 			length = 0;
 		}
 	}
 
+	if (rabin_pos && last_offset < *size) {
+		*rabin_pos = last_offset;
+		return (0);
+	}
 	// If we found at least a few chunks, perform dedup.
 	if (blknum > 2) {
 		uint64_t prev_cksum;

rabin/rabin_polynomial.h

@@ -144,7 +144,7 @@ extern rabin_context_t *create_rabin_context(uint64_t chunksize, uint64_t real_c
 	const char *algo);
 extern void destroy_rabin_context(rabin_context_t *ctx);
 extern unsigned int rabin_dedup(rabin_context_t *ctx, unsigned char *buf, 
-	ssize_t *size, ssize_t offset);
+	ssize_t *size, ssize_t offset, ssize_t *rabin_pos);
 extern void rabin_inverse_dedup(rabin_context_t *ctx, uchar_t *buf, ssize_t *size);
 extern void rabin_parse_hdr(uchar_t *buf, unsigned int *blknum, ssize_t *rabin_index_sz,
 		ssize_t *rabin_data_sz, ssize_t *rabin_index_sz_cmp,

utils.c

@@ -194,6 +194,39 @@ Read(int fd, void *buf, size_t count)
 	return (count - rem);
 }
 
+/*
+ * Read the requested chunk and return the last rabin boundary in the chunk.
+ * This helps in splitting chunks at rabin boundaries rather than fixed points.
+ * The request buffer may have some data at the beginning carried over from
+ * after the previous rabin boundary.
+ */
+ssize_t
+Read_Adjusted(int fd, uchar_t *buf, size_t count, ssize_t *rabin_count, void *ctx)
+{
+        char *buf2;
+        ssize_t rcount;
+        rabin_context_t *rctx = (rabin_context_t *)ctx;
+
+        if (!ctx)  return (Read(fd, buf, count));
+        buf2 = buf;
+        if (*rabin_count) {
+                buf2 = (char *)buf + *rabin_count;
+                count -= *rabin_count;
+        }
+        rcount = Read(fd, buf2, count);
+        if (rcount > 0) {
+                rcount += *rabin_count;
+		if (!rcount < count)
+			rabin_dedup(rctx, buf, &rcount, *rabin_count, rabin_count);
+		else
+			*rabin_count = 0;
+        } else {
+                if (rcount == 0) rcount = *rabin_count;
+                *rabin_count = 0;
+        }
+        return (rcount);
+}
+
 ssize_t
 Write(int fd, const void *buf, size_t count)
 {