The existing implementation uses a switch with
many conditions, that when compiled is translated
to a not optimal series of conditional jumps.
With a lookup table the generated code has less conditional jumps,
that should translate in improving the CPU ability to predict the
jumps.
Performance Comparison:
All the timings are in nanoseconds, "OVS Master" corresponds to 13a1d36.
N is the number of repetitions
Serialize vswitch.ovsschema
N OVS Master Lookup Table Difference Diff per op
1 233182 200369 32813 32813
10 2724931 1919168 805763 80576.3
100 22802794 24406648 -1603854 -16038.54
1000 253645888 206259760 47386128 47386.128
10000 2352245703 1906839780 445405923 44540.5923
100000 23967770920 19012178655 4955592265 49555.92265
Serialize echo example
N OVS Master Lookup Table Difference Diff per op
1 3857 12565 -8708 -8708
10 17403 7312 10091 1009.1
100 57859 56613 1246 12.46
1000 592310 528110 64200 64.2
10000 6096334 5576109 520225 52.0225
100000 60970439 58477626 2492813 24.92813
Serialize mutate example
N OVS Master Lookup Table Difference Diff per op
1 7115 19051 -11936 -11936
10 34110 39561 -5451 -545.1
100 296613 298645 -2032 -20.32
1000 3510499 2930588 579911 579.911
10000 33898710 30278631 3620079 362.0079
100000 305069356 280622992 24446364 244.46364
Signed-off-by: Esteban Rodriguez Betancourt <esteb...@hpe.com>
---
I can't believe that I didn't send the patch in the previous mail, sorry about
that.
Regards,
Esteban
lib/json.c | 76 +++++++++++++++++++++++++++++++++-----------------------------
1 file changed, 40 insertions(+), 36 deletions(-)
diff --git a/lib/json.c b/lib/json.c
index 995f3c2..080e881 100644
--- a/lib/json.c
+++ b/lib/json.c
@@ -1610,49 +1610,53 @@ json_serialize_array(const struct json_array *array,
struct json_serializer *s)
ds_put_char(ds, ']');
}
+const char *chars_escaping[256] = {
+ "\\u0000", "\\u0001", "\\u0002", "\\u0003", "\\u0004", "\\u0005",
"\\u0006", "\\u0007",
+ "\\b", "\\t", "\\n", "\\u000b", "\\f", "\\r", "\\u000e", "\\u000f",
+ "\\u0010", "\\u0011", "\\u0012", "\\u0013", "\\u0014", "\\u0015",
"\\u0016", "\\u0017",
+ "\\u0018", "\\u0019", "\\u001a", "\\u001b", "\\u001c", "\\u001d",
"\\u001e", "\\u001f",
+ " ", "!", "\\\"", "#", "$", "%", "&", "'",
+ "(", ")", "*", "+", ",", "-", ".", "/",
+ "0", "1", "2", "3", "4", "5", "6", "7",
+ "8", "9", ":", ";", "<", "=", ">", "?",
+ "@", "A", "B", "C", "D", "E", "F", "G",
+ "H", "I", "J", "K", "L", "M", "N", "O",
+ "P", "Q", "R", "S", "T", "U", "V", "W",
+ "X", "Y", "Z", "[", "\\\\", "]", "^", "_",
+ "`", "a", "b", "c", "d", "e", "f", "g",
+ "h", "i", "j", "k", "l", "m", "n", "o",
+ "p", "q", "r", "s", "t", "u", "v", "w",
+ "x", "y", "z", "{", "|", "}", "~", "\x7f",
+ "\x80", "\x81", "\x82", "\x83", "\x84", "\x85", "\x86", "\x87",
+ "\x88", "\x89", "\x8a", "\x8b", "\x8c", "\x8d", "\x8e", "\x8f",
+ "\x90", "\x91", "\x92", "\x93", "\x94", "\x95", "\x96", "\x97",
+ "\x98", "\x99", "\x9a", "\x9b", "\x9c", "\x9d", "\x9e", "\x9f",
+ "\xa0", "\xa1", "\xa2", "\xa3", "\xa4", "\xa5", "\xa6", "\xa7",
+ "\xa8", "\xa9", "\xaa", "\xab", "\xac", "\xad", "\xae", "\xaf",
+ "\xb0", "\xb1", "\xb2", "\xb3", "\xb4", "\xb5", "\xb6", "\xb7",
+ "\xb8", "\xb9", "\xba", "\xbb", "\xbc", "\xbd", "\xbe", "\xbf",
+ "\xc0", "\xc1", "\xc2", "\xc3", "\xc4", "\xc5", "\xc6", "\xc7",
+ "\xc8", "\xc9", "\xca", "\xcb", "\xcc", "\xcd", "\xce", "\xcf",
+ "\xd0", "\xd1", "\xd2", "\xd3", "\xd4", "\xd5", "\xd6", "\xd7",
+ "\xd8", "\xd9", "\xda", "\xdb", "\xdc", "\xdd", "\xde", "\xdf",
+ "\xe0", "\xe1", "\xe2", "\xe3", "\xe4", "\xe5", "\xe6", "\xe7",
+ "\xe8", "\xe9", "\xea", "\xeb", "\xec", "\xed", "\xee", "\xef",
+ "\xf0", "\xf1", "\xf2", "\xf3", "\xf4", "\xf5", "\xf6", "\xf7",
+ "\xf8", "\xf9", "\xfa", "\xfb", "\xfc", "\xfd", "\xfe", "\xff"
+};
+
static void
json_serialize_string(const char *string, struct ds *ds)
{
uint8_t c;
+ uint8_t c2;
+ const char *escape;
ds_put_char(ds, '"');
while ((c = *string++) != '\0') {
- switch (c) {
- case '"':
- ds_put_cstr(ds, "\\\"");
- break;
-
- case '\\':
- ds_put_cstr(ds, "\\\\");
- break;
-
- case '\b':
- ds_put_cstr(ds, "\\b");
- break;
-
- case '\f':
- ds_put_cstr(ds, "\\f");
- break;
-
- case '\n':
- ds_put_cstr(ds, "\\n");
- break;
-
- case '\r':
- ds_put_cstr(ds, "\\r");
- break;
-
- case '\t':
- ds_put_cstr(ds, "\\t");
- break;
-
- default:
- if (c >= 32) {
- ds_put_char(ds, c);
- } else {
- ds_put_format(ds, "\\u%04x", c);
- }
- break;
+ escape = chars_escaping[c];
+ while ((c2 = *escape++) != '\0') {
+ ds_put_char(ds, c2);
}
}
ds_put_char(ds, '"');
--
2.7.4
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