Change Segmented Dedupe flow to improve parallelism.

Periodically sync writes to segcache file.
Use simple insertion sort for small numbers of elements.

rabin/global/index.c

@@ -313,6 +313,12 @@ db_segcache_write(archive_config_t *cfg, int tid, uchar_t *buf, uint32_t len, ui
 	return (0);
 }
 
+void
+db_segcache_sync(archive_config_t *cfg)
+{
+	fdatasync(cfg->seg_fd_w);
+}
+
 /*
  * Get the current file pointer position of the metadata file. This indicates the
  * position where the next entry will be added.

rabin/global/index.h

@@ -55,6 +55,7 @@ hash_entry_t *db_lookup_insert_s(archive_config_t *cfg, uchar_t *sim_cksum, int
 void destroy_global_db_s(archive_config_t *cfg);
 
 int db_segcache_write(archive_config_t *cfg, int tid, uchar_t *buf, uint32_t len, uint32_t blknum, uint64_t file_offset);
+void db_segcache_sync(archive_config_t *cfg);
 int db_segcache_pos(archive_config_t *cfg, int tid);
 int db_segcache_map(archive_config_t *cfg, int tid, uint32_t *blknum, uint64_t *offset, uchar_t **blocks);
 int db_segcache_unmap(archive_config_t *cfg, int tid);

rabin/rabin_dedup.c

@@ -380,6 +380,34 @@ destroy_dedupe_context(dedupe_context_t *ctx)
 	}
 }
 
+/*
+ * Simple insertion sort of integers. Used for sorting a small number of items to
+ * avoid overheads of qsort() with callback function.
+ */
+static void
+isort_uint64(uint64_t *ary, uint32_t nitems)
+{
+	uint32_t i, j, k;
+	uint64_t tmp;
+
+	for (i = 1 ; i < nitems; i++) {
+		for (j = 0 ; j < i ; j++) {
+			if (ary[j] > ary[i]) {
+				tmp = ary[j] ;
+				ary[j] = ary[i] ;
+
+				for (k = i ; k > j ; k--)
+					ary[k] = ary[k - 1] ;
+
+				ary[k + 1] = tmp ;
+			}
+		}
+	}
+}
+
+/*
+ * Callback for qsort() for 64-bit min-values list in hash values.
+ */
 int
 cmpint(const void *a, const void *b)
 {
@@ -823,7 +851,7 @@ process_blocks:
 				g_dedupe_idx += (RABIN_ENTRY_SIZE * 2);
 
 			} else {
-				uchar_t *seg_heap, *sim_ck;
+				uchar_t *seg_heap, *sim_ck, *sim_offsets;
 				archive_config_t *cfg;
 				uint32_t increment, len, blks, o_blks, k;
 				global_blockentry_t *seg_blocks;
@@ -836,10 +864,16 @@ process_blocks:
 				 * in-memory index for very large datasets.
 				 * ======================================================================
 				 */
+
 				cfg = ctx->arc;
+				assert(cfg->similarity_cksum_sz >= sizeof (uint64_t));
 				seg_heap = (uchar_t *)(ctx->g_blocks) - cfg->segment_sz * cfg->chunk_cksum_sz;
+				ary_sz = (cfg->sub_intervals * cfg->similarity_cksum_sz + sizeof (blks) + 1) *
+				    ((blknum+1) / cfg->segment_sz) + 3;
+				sim_offsets = seg_heap - ary_sz;
+				src = sim_offsets;
 				ary_sz = cfg->segment_sz * sizeof (global_blockentry_t **);
-				htab = (global_blockentry_t **)(seg_heap - ary_sz);
+				htab = (global_blockentry_t **)(src - ary_sz);
 				for (i=0; i<blknum;) {
 					uint64_t crc, off1;
 					length = 0;
@@ -856,6 +890,8 @@ process_blocks:
 						length += cfg->chunk_cksum_sz;
 						tgt += cfg->chunk_cksum_sz;
 					}
+					*((uint32_t *)src) = blks;
+					src += sizeof (blks);
 					blks = j+i;
 
 					/*
@@ -890,11 +926,88 @@ process_blocks:
 						DEBUG_STAT_EN(w2 = get_wtime_millis());
 					}
 
-					sim_ck -= cfg->similarity_cksum_sz;
 					seg_offset = db_segcache_pos(cfg, ctx->id);
-					src = (uchar_t *)&(ctx->g_blocks[i]);
 					len = blks * sizeof (global_blockentry_t);
-					db_segcache_write(cfg, ctx->id, src, len, blks-i, ctx->file_offset);
+					db_segcache_write(cfg, ctx->id, (uchar_t *)&(ctx->g_blocks[i]),
+					    len, blks-i, ctx->file_offset);
+
+					/*
+					 * Now lookup all the similarity hashes. We sort the hashes first so that
+					 * all duplicate hash values can be easily eliminated.
+					 * 
+					 * The matching segment offsets in the segcache are stored in a list.
+					 */
+					if (cfg->similarity_cksum_sz == 8) {
+						isort_uint64((uint64_t *)(ctx->similarity_cksums), sub_i);
+					} else {
+						fprintf(stderr, "Similarity Checksum Size: %d not implemented.\n",
+							cfg->similarity_cksum_sz);
+						ctx->valid = 0;
+						sem_post(ctx->index_sem_next);
+						return (0);
+					}
+
+					sim_ck = ctx->similarity_cksums;
+					tgt = src + 1; // One byte for number of entries
+					crc = 0;
+					off1 = UINT64_MAX;
+					k = 0;
+					for (j=0; j < sub_i; j++) {
+						hash_entry_t *he = NULL;
+
+						/*
+						 * Check for duplicate checksum which need not be looked up
+						 * again.
+						 */
+						if (crc == *((uint64_t *)sim_ck)) {
+							he = NULL;
+						} else {
+							he = db_lookup_insert_s(cfg, sim_ck, 0, seg_offset, 0, 1);
+							/*
+							 * Check for different checksum but same segment match.
+							 * This is not a complete check but does help to reduce
+							 * wasted processing.
+							 */
+							if (he && off1 == he->item_offset) {
+								crc = *((uint64_t *)sim_ck);
+								he = NULL;
+							}
+						}
+						if (he) {
+							crc = *((uint64_t *)sim_ck);
+							off1 = he->item_offset;
+							*((uint64_t *)tgt) = off1;
+							tgt += cfg->similarity_cksum_sz;
+							k++;
+						}
+						sim_ck += cfg->similarity_cksum_sz;
+					}
+					*src = k; // Number of entries
+					src++;
+
+					/*
+					 * At this point we have a list of segment offsets from the segcache
+					 * file. Sort the offsets to avoid subsequent random access.
+					 */
+					isort_uint64((uint64_t *)src, k);
+					src = tgt;
+					i = blks;
+				}
+
+				/*
+				 * Signal the next thread in sequence to access the index.
+				 */
+				sem_post(ctx->index_sem_next);
+				db_segcache_sync(cfg);
+
+				/*
+				 * Now go through all the matching segments for all the current segments
+				 * and perform actual deduplication.
+				 */
+				src = sim_offsets;
+				for (i=0; i<blknum;) {
+					blks = *((uint32_t *)src) + i;
+					src += sizeof (blks);
 
 					/*
 					 * Insert current segment blocks into local hashtable and do partial
@@ -944,44 +1057,21 @@ process_blocks:
 					}
 
 					/*
-					 * Now lookup all the similarity hashes. We sort the hashes first so that
+					 * Now go through segment match list which was prepared earlier
-					 * all duplicate hash values can be easily eliminated.
+					 * and deduplicate with the matching segment blocks.
 					 */
-					qsort(ctx->similarity_cksums, sub_i, 8, cmpint);
+					sub_i = *src;
-					crc = 0;
+					src++;
-					off1 = UINT64_MAX;
+					sim_ck = src;
-					for (j=sub_i; j > 0; j--) {
+					for (j=0; j < sub_i; j++) {
-						hash_entry_t *he = NULL;
-
 						/*
-						 * Check for duplicate checksum which need not be looked up
+						 * Load segment metadata from disk and perform identity deduplication
-						 * again.
+						 * with the segment chunks.
 						 */
-						if (crc == *((uint64_t *)sim_ck)) {
+						offset = *((uint64_t *)sim_ck);
-							he = NULL;
-						} else {
-							he = db_lookup_insert_s(cfg, sim_ck, 0, seg_offset, 0, 1);
-							/*
-							 * Check for different checksum but same segment match.
-							 * This is not a complete check but does help to reduce
-							 * wasted processing.
-							 */
-							if (he && off1 == he->item_offset) {
-								crc = *((uint64_t *)sim_ck);
-								he = NULL;
-							}
-						}
-						if (he) {
-							/*
-							 * Match found. Load segment metadata from disk and perform
-							 * identity deduplication with the segment chunks.
-							 */
-							crc = *((uint64_t *)sim_ck);
-							offset = he->item_offset;
-							off1 = offset;
 						if (db_segcache_map(cfg, ctx->id, &o_blks, &offset,
 						    (uchar_t **)&seg_blocks) == -1) {
-								fprintf(stderr, "Segment cache mmap failed.\n");
+							fprintf(stderr, "** Segment cache mmap failed.\n");
 							ctx->valid = 0;
 							return (0);
 						}
@@ -1020,17 +1110,12 @@ next_ent:
 								} while(1);
 							}
 						}
+						sim_ck += cfg->similarity_cksum_sz;
 					}
-						sim_ck -= cfg->similarity_cksum_sz;
+					src = sim_ck;
-					}
 					i = blks;
 				}
 
-				/*
-				 * Signal the next thread in sequence to access the index.
-				 */
-				sem_post(ctx->index_sem_next);
-
 				/*======================================================================
 				 * Finally scan the blocks array and update dedupe index.
 				 *======================================================================