From: Martin Mares <mj@ucw.cz>
Date: Sat, 10 Feb 2007 18:05:13 +0000 (+0100)
Subject: Much better decisions on radix sorter parameters.
X-Git-Tag: holmes-import~506^2~13^2~149
X-Git-Url: http://mj.ucw.cz/gitweb/?a=commitdiff_plain;h=ae3892dc4f3c3a759315969e2ab5156f034707b2;p=libucw.git

Much better decisions on radix sorter parameters.
---

diff --git a/lib/sorter/common.h b/lib/sorter/common.h
index 3097ea2d..504afda1 100644
--- a/lib/sorter/common.h
+++ b/lib/sorter/common.h
@@ -14,7 +14,7 @@
 
 /* Configuration, some of the variables are used by the old sorter, too. */
 extern uns sorter_trace, sorter_presort_bufsize, sorter_stream_bufsize;
-extern uns sorter_debug;
+extern uns sorter_debug, sorter_min_radix_bits, sorter_max_radix_bits;
 extern u64 sorter_bufsize;
 
 #define SORT_TRACE(x...) do { if (sorter_trace) log(L_DEBUG, x); } while(0)
@@ -41,12 +41,18 @@ struct sort_context {
   size_t big_buf_size, big_buf_half_size;
 
   int (*custom_presort)(struct fastbuf *dest, void *buf, size_t bufsize);
+
   // Take as much as possible from the source bucket, sort it in memory and dump to destination bucket.
   // Return 1 if there is more data available in the source bucket.
   int (*internal_sort)(struct sort_context *ctx, struct sort_bucket *in, struct sort_bucket *out, struct sort_bucket *out_only);
+
+  // Estimate how much input data from `b' will fit in the internal sorting buffer.
+  u64 (*internal_estimate)(struct sort_context *ctx, struct sort_bucket *b);
+
   // Two-way split/merge: merge up to 2 source buckets to up to 2 destination buckets.
   // Bucket arrays are NULL-terminated.
   void (*twoway_merge)(struct sort_context *ctx, struct sort_bucket **ins, struct sort_bucket **outs);
+
   // Radix split according to hash function
   void (*radix_split)(struct sort_context *ctx, struct sort_bucket *in, struct sort_bucket **outs, uns bitpos, uns numbits);
 
@@ -63,6 +69,7 @@ void sorter_run(struct sort_context *ctx);
 /* Buffers */
 
 void *sorter_alloc(struct sort_context *ctx, uns size);
+void sorter_prepare_buf(struct sort_context *ctx);
 void sorter_alloc_buf(struct sort_context *ctx);
 void sorter_free_buf(struct sort_context *ctx);
 
diff --git a/lib/sorter/config.c b/lib/sorter/config.c
index 26581902..60dca3da 100644
--- a/lib/sorter/config.c
+++ b/lib/sorter/config.c
@@ -17,6 +17,8 @@ uns sorter_presort_bufsize = 65536;
 uns sorter_stream_bufsize = 65536;
 u64 sorter_bufsize = 65536;
 uns sorter_debug;
+uns sorter_min_radix_bits;
+uns sorter_max_radix_bits;
 
 static struct cf_section sorter_config = {
   CF_ITEMS {
@@ -25,6 +27,8 @@ static struct cf_section sorter_config = {
     CF_UNS("StreamBuffer", &sorter_stream_bufsize),
     CF_U64("SortBuffer", &sorter_bufsize),
     CF_UNS("Debug", &sorter_debug),
+    CF_UNS("MinRadixBits", &sorter_min_radix_bits),
+    CF_UNS("MaxRadixBits", &sorter_max_radix_bits),
     CF_END
   }
 };
diff --git a/lib/sorter/govern.c b/lib/sorter/govern.c
index b15b5eab..388fac4a 100644
--- a/lib/sorter/govern.c
+++ b/lib/sorter/govern.c
@@ -168,20 +168,30 @@ sorter_twoway(struct sort_context *ctx, struct sort_bucket *b)
   clist_insert_after(&ins[0]->n, list_pos);
 }
 
-static int
-sorter_radix_p(struct sort_context *ctx, struct sort_bucket *b)
+static uns
+sorter_radix_bits(struct sort_context *ctx, struct sort_bucket *b)
 {
-  return b->hash_bits && ctx->radix_split &&
-    !(sorter_debug & SORT_DEBUG_NO_RADIX) &&
-    sbuck_size(b) > (sh_off_t)sorter_bufsize;
+  if (!b->hash_bits || !ctx->radix_split || (sorter_debug & SORT_DEBUG_NO_RADIX))
+    return 0;
+
+  u64 in = sbuck_size(b);
+  u64 mem = ctx->internal_estimate(ctx, b);
+  if (in < mem)
+    return 0;
+
+  uns n;
+  for (n = sorter_min_radix_bits; n < sorter_max_radix_bits && n < b->hash_bits; n++)
+    if ((in >> n) < mem)
+      break;
+  return n;
 }
 
 static void
-sorter_radix(struct sort_context *ctx, struct sort_bucket *b)
+    sorter_radix(struct sort_context *ctx, struct sort_bucket *b, uns bits)
 {
-  uns bits = MIN(b->hash_bits, 4);	/* FIXME */
   uns nbuck = 1 << bits;
-  SORT_XTRACE(2, "Running radix sort on %s with %d bits of %d", F_BSIZE(b), bits, b->hash_bits);
+  SORT_XTRACE(2, "Running radix sort on %s with %d bits of %d (expected size %s)",
+	      F_BSIZE(b), bits, b->hash_bits, stk_fsize(sbuck_size(b) / nbuck));
   sorter_start_timer(ctx);
 
   struct sort_bucket **outs = alloca(nbuck * sizeof(struct sort_bucket *));
@@ -201,6 +211,8 @@ sorter_radix(struct sort_context *ctx, struct sort_bucket *b)
       min = MIN(min, s);
       max = MAX(max, s);
       sum += s;
+      if (nbuck > 4)
+	sbuck_swap_out(outs[i]);
     }
 
   SORT_TRACE("Radix split (%d buckets, %s min, %s max, %s avg, %dMB/s)", nbuck,
@@ -213,6 +225,7 @@ sorter_run(struct sort_context *ctx)
 {
   ctx->pool = mp_new(4096);
   clist_init(&ctx->bucket_list);
+  sorter_prepare_buf(ctx);
 
   /* FIXME: Remember to test sorting of empty files */
 
@@ -239,6 +252,7 @@ sorter_run(struct sort_context *ctx)
   clist_add_head(&ctx->bucket_list, &bout->n);
 
   struct sort_bucket *b;
+  uns bits;
   while (bout = clist_head(&ctx->bucket_list), b = clist_next(&ctx->bucket_list, &bout->n))
     {
       SORT_XTRACE(2, "Next block: %s, %d hash bits", F_BSIZE(b), b->hash_bits);
@@ -246,8 +260,8 @@ sorter_run(struct sort_context *ctx)
 	sbuck_drop(b);
       else if (b->runs == 1)
 	sorter_join(b);
-      else if (sorter_radix_p(ctx, b))
-	sorter_radix(ctx, b);
+      else if (bits = sorter_radix_bits(ctx, b))
+	sorter_radix(ctx, b, bits);
       else
 	sorter_twoway(ctx, b);
     }
diff --git a/lib/sorter/s-fixint.h b/lib/sorter/s-fixint.h
index a36be558..2eca66ff 100644
--- a/lib/sorter/s-fixint.h
+++ b/lib/sorter/s-fixint.h
@@ -57,3 +57,9 @@ static int P(internal)(struct sort_context *ctx, struct sort_bucket *bin, struct
 
   return (n == maxkeys);
 }
+
+static u64
+P(internal_estimate)(struct sort_context *ctx, struct sort_bucket *b UNUSED)
+{
+  return ctx->big_buf_half_size;
+}
diff --git a/lib/sorter/s-internal.h b/lib/sorter/s-internal.h
index a3c38128..05fc7e98 100644
--- a/lib/sorter/s-internal.h
+++ b/lib/sorter/s-internal.h
@@ -137,3 +137,16 @@ static int P(internal)(struct sort_context *ctx, struct sort_bucket *bin, struct
 
   return ctx->more_keys;
 }
+
+static u64
+P(internal_estimate)(struct sort_context *ctx, struct sort_bucket *b UNUSED)
+{
+  uns avg;
+#ifdef SORT_VAR_KEY
+  avg = ALIGN_TO(sizeof(P(key))/4, CPU_STRUCT_ALIGN);	// Wild guess...
+#else
+  avg = ALIGN_TO(sizeof(P(key)), CPU_STRUCT_ALIGN);
+#endif
+  // We ignore the data part of records, it probably won't make the estimate much worse
+  return (ctx->big_buf_half_size / (avg + sizeof(P(internal_item_t))) * avg);
+}
diff --git a/lib/sorter/sbuck.c b/lib/sorter/sbuck.c
index b1297c15..515115e2 100644
--- a/lib/sorter/sbuck.c
+++ b/lib/sorter/sbuck.c
@@ -135,17 +135,22 @@ sbuck_swap_out(struct sort_bucket *b)
 }
 
 void
-sorter_alloc_buf(struct sort_context *ctx)
+sorter_prepare_buf(struct sort_context *ctx)
 {
-  if (ctx->big_buf)
-    return;
   u64 bs = MAX(sorter_bufsize/2, 1);
   bs = ALIGN_TO(bs, (u64)CPU_PAGE_SIZE);
-  ctx->big_buf = big_alloc(2*bs);
   ctx->big_buf_size = 2*bs;
-  ctx->big_buf_half = ((byte*) ctx->big_buf) + bs;
   ctx->big_buf_half_size = bs;
-  SORT_XTRACE(2, "Allocated sorting buffer (2*%s)", stk_fsize(bs));
+}
+
+void
+sorter_alloc_buf(struct sort_context *ctx)
+{
+  if (ctx->big_buf)
+    return;
+  ctx->big_buf = big_alloc(ctx->big_buf_size);
+  ctx->big_buf_half = ((byte*) ctx->big_buf) + ctx->big_buf_half_size;
+  SORT_XTRACE(2, "Allocated sorting buffer (2*%s)", stk_fsize(ctx->big_buf_half_size));
 }
 
 void
diff --git a/lib/sorter/sorter.h b/lib/sorter/sorter.h
index 39bdcb97..89cf9f0d 100644
--- a/lib/sorter/sorter.h
+++ b/lib/sorter/sorter.h
@@ -241,6 +241,7 @@ static struct fastbuf *P(sort)(
 #endif
 
   ctx.internal_sort = P(internal);
+  ctx.internal_estimate = P(internal_estimate);
   ctx.twoway_merge = P(twoway_merge);
 
   sorter_run(&ctx);