On Tue, 10 Aug 2010 11:59:25 -0400 James Carlson <carls...@workingcode.com> wrote:
> I'm afraid I don't follow the example. How is it that getting data > from the network (which involves at least a read() system call and > data copying) isn't several orders of magnitude slower than getting > the current time of day? How is it that clock_gettime() isn't > completely buried in the noise? It depends on what your application is doing, and how fast/slow clock_gettime() is. For example a quick test on Linux shows that on average calling clock_gettime() is 1.6 times slower than calling read() on /etc/passwd. If you can decrease system time by 1.6 times, that's a big improvement. Another example, you cache file data in memory. Suppose this data is dynamically generated by an fcgi script, or similar, hence you don't want to cache it for more than 5 seconds. For every file you find in cache, you need to get current time and calculate if the file has expired and needs to be reloaded, or can be served from cache. If the rate at which you scan your cache is high, calling clock_gettime() for every file will add to your system time. In fact, calling clock_gettime every second would be sufficient. _______________________________________________ opensolaris-code mailing list opensolaris-code@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/opensolaris-code
