Hi folks, While running rally in OpenStack we found out that ovn-northd was at 100% CPU most of the time. It doesn't have to be necessarily a problem but I wanted to do a simple profiling by running a rally task which creates a network (Logical Switch) and creates 6 ports on it, repeating the whole operation 1000 times. The ports are networks are also deleted.
I used master branch and compiled it with -O1: CFLAGS="-O1 -g" ./configure --prefix=/usr/local/ --with-linux=/usr/lib/modules/`ls /usr/lib/modules/ | tail -n 1`/build gcc version 4.8.5 20150623 (Red Hat 4.8.5-16) (GCC) What I saw is that ~ 15% of the execution time was spent in uuid_from_string() function in util/uuid.c module which calls hexits_value() which ends up calling hexit_value(). This last function gets called >1M times. I thought that it was worth to inline hexit_value() and use a lookup table instead the switch/case [0] so I did it (find the patch below) and the gain is that instead of a 14%, uuid_from_string() now takes a 9% of the total execution time. See [1]. [0] https://github.com/openvswitch/ovs/blob/79feb3b0de83932c6cbf761d70051330db4d07f7/lib/util.c#L844 [1] https://imgur.com/a/3gzDF Patch: Note that we could make the table smaller to optimize the data cache usage but then we would have to accommodate the argument and include extra checks. ------------------------------------------------------- diff --git a/lib/util.c b/lib/util.c index a4d22df0c..a24472690 100644 --- a/lib/util.c +++ b/lib/util.c @@ -839,38 +839,6 @@ str_to_double(const char *s, double *d) } } -/* Returns the value of 'c' as a hexadecimal digit. */ -int -hexit_value(int c) -{ - switch (c) { - case '0': case '1': case '2': case '3': case '4': - case '5': case '6': case '7': case '8': case '9': - return c - '0'; - - case 'a': case 'A': - return 0xa; - - case 'b': case 'B': - return 0xb; - - case 'c': case 'C': - return 0xc; - - case 'd': case 'D': - return 0xd; - - case 'e': case 'E': - return 0xe; - - case 'f': case 'F': - return 0xf; - - default: - return -1; - } -} - /* Returns the integer value of the 'n' hexadecimal digits starting at 's', or * UINTMAX_MAX if one of those "digits" is not really a hex digit. Sets '*ok' * to true if the conversion succeeds or to false if a non-hex digit is diff --git a/lib/util.h b/lib/util.h index b6639b8b8..f41e2a030 100644 --- a/lib/util.h +++ b/lib/util.h @@ -217,7 +217,28 @@ bool ovs_scan_len(const char *s, int *n, const char *format, ...); bool str_to_double(const char *, double *); -int hexit_value(int c); + +static const char hextable[] = { + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1, 0,1,2,3,4,5,6,7,8,9,-1,-1,-1,-1,-1,-1,-1,10,11,12,13,14,15,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, + -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1 +}; + +/* Returns the value of 'c' as a hexadecimal digit. */ +static inline int +hexit_value(int c) +{ + return hextable[c & 0xff]; +} + uintmax_t hexits_value(const char *s, size_t n, bool *ok); int parse_int_string(const char *s, uint8_t *valuep, int field_width, -------------------------------------------------------
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