From: Aurelien LAJOIE <orel@melix.net>
To: util-linux@vger.kernel.org
Cc: Aurelien LAJOIE <orel@melix.net>
Subject: [PATCH v2] libuuid: improve uuid_unparse() performance
Date: Thu, 26 Mar 2020 15:38:27 +0100 [thread overview]
Message-ID: <20200326143827.25879-1-orel@melix.net> (raw)
There is 2 improvements:
* remove useless uuid_unpack,
* directly print the hexa format from memory without using printf
we can do this as the bytes order is the network byte order
https://tools.ietf.org/html/rfc4122#section-4.1.2
even the spatially unique node identifier(the last 6 bytes)
The improvement is important, some results for 1000000 uuid_unparse calls:
Little Endian Ubuntu:
before took 382623 us
after took 36740 us
Big Endian OpenBSD:
before took 3138172 us
after took 180116 us
Signed-off-by: Aurelien LAJOIE <orel@melix.net>
---
libuuid/src/unparse.c | 45 ++++++++++++++++++++-----------------------
1 file changed, 21 insertions(+), 24 deletions(-)
diff --git a/libuuid/src/unparse.c b/libuuid/src/unparse.c
index a95bbb042..0e7e8eae4 100644
--- a/libuuid/src/unparse.c
+++ b/libuuid/src/unparse.c
@@ -36,41 +36,38 @@
#include "uuidP.h"
-static const char *fmt_lower =
- "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x";
+static char const hexdigits_lower[16] = "0123456789abcdef";
+static char const hexdigits_upper[16] = "0123456789ABCDEF";
-static const char *fmt_upper =
- "%08X-%04X-%04X-%02X%02X-%02X%02X%02X%02X%02X%02X";
-
-#ifdef UUID_UNPARSE_DEFAULT_UPPER
-#define FMT_DEFAULT fmt_upper
-#else
-#define FMT_DEFAULT fmt_lower
-#endif
-
-static void uuid_unparse_x(const uuid_t uu, char *out, const char *fmt)
+static void uuid_fmt(const uuid_t uuid, char *buf, char const fmt[restrict])
{
- struct uuid uuid;
+ char *p = buf;
- uuid_unpack(uu, &uuid);
- sprintf(out, fmt,
- uuid.time_low, uuid.time_mid, uuid.time_hi_and_version,
- uuid.clock_seq >> 8, uuid.clock_seq & 0xFF,
- uuid.node[0], uuid.node[1], uuid.node[2],
- uuid.node[3], uuid.node[4], uuid.node[5]);
+ for (int i = 0; i < 16; i++) {
+ if (i == 4 || i == 6 || i == 8 || i == 10) {
+ *p++ = '-';
+ }
+ size_t tmp = uuid[i];
+ *p++ = fmt[tmp >> 4];
+ *p++ = fmt[tmp & 15];
+ }
+ *p = '\0';
}
void uuid_unparse_lower(const uuid_t uu, char *out)
{
- uuid_unparse_x(uu, out, fmt_lower);
+ uuid_fmt(uu, out, hexdigits_lower);
}
void uuid_unparse_upper(const uuid_t uu, char *out)
{
- uuid_unparse_x(uu, out, fmt_upper);
+ uuid_fmt(uu, out, hexdigits_upper);
}
+#ifdef UUID_UNPARSE_DEFAULT_UPPER
void uuid_unparse(const uuid_t uu, char *out)
-{
- uuid_unparse_x(uu, out, FMT_DEFAULT);
-}
+ __attribute__((alias("uuid_unparse_upper")));
+#else
+void uuid_unparse(const uuid_t uu, char *out)
+ __attribute__((alias("uuid_unparse_lower")));
+#endif
--
2.20.1
next reply other threads:[~2020-03-26 14:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 14:38 Aurelien LAJOIE [this message]
2020-03-31 13:30 ` [PATCH v2] libuuid: improve uuid_unparse() performance Karel Zak
2020-04-01 8:31 ` Karel Zak
2020-04-01 9:34 ` Peter Cordes
2020-04-01 10:00 ` Karel Zak
2020-04-01 10:05 ` Karel Zak
2020-04-01 11:09 ` Peter Cordes
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