Improve yield strategy for list_to_binary()/binary_to_list()

Avoid yield in the BIF when input is small. This either yielding
before beginning to work in the BIF, or by allowing some more
reductions before yielding.

1 files changed, 74 insertions, 7 deletions

diff --git a/erts/emulator/beam/binary.c b/erts/emulator/beam/binary.c
index e670fbf31c..d3e481c7f9 100644
--- a/erts/emulator/beam/binary.c
+++ b/erts/emulator/beam/binary.c
@@ -34,6 +34,9 @@
 #include "erl_binary.h"
 #include "erl_bits.h"
 
+#define L2B_B2L_MIN_EXEC_REDS (CONTEXT_REDS/4)
+#define L2B_B2L_RESCHED_REDS (CONTEXT_REDS/40)
+
 static Export binary_to_list_continue_export;
 static Export list_to_binary_continue_export;
 
@@ -415,10 +418,10 @@ binary_to_list_chunk(Process *c_p,
 }
 
 static ERTS_INLINE BIF_RETTYPE
-binary_to_list(Process *c_p, Eterm *hp, Eterm tail, byte *bytes, Uint size, Uint bitoffs)
+binary_to_list(Process *c_p, Eterm *hp, Eterm tail, byte *bytes,
+	       Uint size, Uint bitoffs, int reds_left, int one_chunk)
 {
-    int reds_left = ERTS_BIF_REDS_LEFT(c_p);
-    if (size < reds_left*ERTS_B2L_BYTES_PER_REDUCTION) {
+    if (one_chunk) {
 	Eterm res;
 	BIF_RETTYPE ret;
 	int bump_reds = (size - 1)/ERTS_B2L_BYTES_PER_REDUCTION + 1;
@@ -472,11 +475,29 @@ BIF_RETTYPE binary_to_list_1(BIF_ALIST_1)
     Uint size;
     Uint bitsize;
     Uint bitoffs;
+    int reds_left;
+    int one_chunk;
 
     if (is_not_binary(BIF_ARG_1)) {
 	goto error;
     }
+
     size = binary_size(BIF_ARG_1);
+    reds_left = ERTS_BIF_REDS_LEFT(BIF_P);
+    one_chunk = size < reds_left*ERTS_B2L_BYTES_PER_REDUCTION;
+    if (!one_chunk) {
+	if (size < L2B_B2L_MIN_EXEC_REDS*ERTS_B2L_BYTES_PER_REDUCTION) {
+	    if (reds_left <= L2B_B2L_RESCHED_REDS) {
+		/* Yield and do it with full context reds... */
+		ERTS_BIF_YIELD1(bif_export[BIF_binary_to_list_1],
+				BIF_P, BIF_ARG_1);
+	    }
+	    /* Allow a bit more reductions... */
+	    one_chunk = 1;
+	    reds_left = L2B_B2L_MIN_EXEC_REDS;
+	}
+    }
+
     ERTS_GET_REAL_BIN(BIF_ARG_1, real_bin, offset, bitoffs, bitsize);
     if (bitsize != 0) {
 	goto error;
@@ -486,7 +507,8 @@ BIF_RETTYPE binary_to_list_1(BIF_ALIST_1)
     } else {
 	Eterm* hp = HAlloc(BIF_P, 2 * size);
 	byte* bytes = binary_bytes(real_bin)+offset;
-	return binary_to_list(BIF_P, hp, NIL, bytes, size, bitoffs);
+	return binary_to_list(BIF_P, hp, NIL, bytes, size,
+			      bitoffs, reds_left, one_chunk);
     }
 
     error:
@@ -505,6 +527,8 @@ BIF_RETTYPE binary_to_list_3(BIF_ALIST_3)
     Uint start;
     Uint stop;
     Eterm* hp;
+    int reds_left;
+    int one_chunk;
 
     if (is_not_binary(BIF_ARG_1)) {
 	goto error;
@@ -513,6 +537,21 @@ BIF_RETTYPE binary_to_list_3(BIF_ALIST_3)
 	goto error;
     }
     size = binary_size(BIF_ARG_1);
+    reds_left = ERTS_BIF_REDS_LEFT(BIF_P);
+    one_chunk = size < reds_left*ERTS_B2L_BYTES_PER_REDUCTION;
+    if (!one_chunk) {
+	if (size < L2B_B2L_MIN_EXEC_REDS*ERTS_B2L_BYTES_PER_REDUCTION) {
+	    if (reds_left <= L2B_B2L_RESCHED_REDS) {
+		/* Yield and do it with full context reds... */
+		ERTS_BIF_YIELD3(bif_export[BIF_binary_to_list_3],
+				BIF_P, BIF_ARG_1, BIF_ARG_2, BIF_ARG_3);
+	    }
+	    /* Allow a bit more reductions... */
+	    one_chunk = 1;
+	    reds_left = L2B_B2L_MIN_EXEC_REDS;
+	}
+    }
+
     ERTS_GET_BINARY_BYTES(BIF_ARG_1, bytes, bitoffs, bitsize);
     if (start < 1 || start > size || stop < 1 ||
 	stop > size || stop < start ) {
@@ -520,7 +559,8 @@ BIF_RETTYPE binary_to_list_3(BIF_ALIST_3)
     }
     i = stop-start+1;
     hp = HAlloc(BIF_P, 2*i);
-    return binary_to_list(BIF_P, hp, NIL, bytes+start-1, i, bitoffs);
+    return binary_to_list(BIF_P, hp, NIL, bytes+start-1, i,
+			  bitoffs, reds_left, one_chunk);
     error:
 	BIF_ERROR(BIF_P, BADARG);
 }
@@ -537,11 +577,27 @@ BIF_RETTYPE bitstring_to_list_1(BIF_ALIST_1)
     byte* bytes;
     Eterm previous = NIL;
     Eterm* hp;
+    int reds_left;
+    int one_chunk;
 
     if (is_not_binary(BIF_ARG_1)) {
 	BIF_ERROR(BIF_P, BADARG);
     }
     size = binary_size(BIF_ARG_1);
+    reds_left = ERTS_BIF_REDS_LEFT(BIF_P);
+    one_chunk = size < reds_left*ERTS_B2L_BYTES_PER_REDUCTION;
+    if (!one_chunk) {
+	if (size < L2B_B2L_MIN_EXEC_REDS*ERTS_B2L_BYTES_PER_REDUCTION) {
+	    if (reds_left <= L2B_B2L_RESCHED_REDS) {
+		/* Yield and do it with full context reds... */
+		ERTS_BIF_YIELD1(bif_export[BIF_bitstring_to_list_1],
+				BIF_P, BIF_ARG_1);
+	    }
+	    /* Allow a bit more reductions... */
+	    one_chunk = 1;
+	    reds_left = L2B_B2L_MIN_EXEC_REDS;
+	}
+    }
     ERTS_GET_REAL_BIN(BIF_ARG_1, real_bin, offset, bitoffs, bitsize);
     bytes = binary_bytes(real_bin)+offset;
     if (bitsize == 0) {
@@ -566,7 +622,8 @@ BIF_RETTYPE bitstring_to_list_1(BIF_ALIST_1)
 	hp += 2;
     }
 
-    return binary_to_list(BIF_P, hp, previous, bytes, size, bitoffs);
+    return binary_to_list(BIF_P, hp, previous, bytes, size,
+			  bitoffs, reds_left, one_chunk);
 }
 
 
@@ -795,8 +852,19 @@ static BIF_RETTYPE list_to_binary_continue(BIF_ALIST_1)
 
 BIF_RETTYPE erts_list_to_binary_bif(Process *c_p, Eterm arg, Export *bif)
 {
+    int orig_reds_left = ERTS_BIF_REDS_LEFT(c_p);
     BIF_RETTYPE ret;
 
+    if (orig_reds_left < L2B_B2L_MIN_EXEC_REDS) {
+	if (orig_reds_left <= L2B_B2L_RESCHED_REDS) {
+	    /* Yield and do it with full context reds... */
+	    ERTS_BIF_PREP_YIELD1(ret, bif, c_p, arg);
+	    return ret;
+	}
+	/* Allow a bit more reductions... */
+	orig_reds_left = L2B_B2L_MIN_EXEC_REDS;
+    }
+
     if (is_nil(arg))
 	ERTS_BIF_PREP_RET(ret, new_binary(c_p, (byte *) "", 0));
     else if (is_not_list(arg))
@@ -818,7 +886,6 @@ BIF_RETTYPE erts_list_to_binary_bif(Process *c_p, Eterm arg, Export *bif)
 						       bif,
 						       erts_iolist_size_yielding,
 						       erts_iolist_to_buf_yielding);
-	    int orig_reds_left = ERTS_BIF_REDS_LEFT(c_p);
 
 	    /*
 	     * First try to do it all at once without having to use