Good blog post explaining the behavior of glibc, I also saw this first hand when profiling Apache awhile back too: http://mail-archives.apache.org/mod_mbox/htt

Good blog post explaining the behavior of glibc, I also saw this first hand when profiling Apache awhile back too: http://mail-archives.apache.org/mod_mbox/httpd-dev/201111.mbox/%3CCAMDeyhzRAZ4eyz%3D%2BstA%3DwoTibM-W6QL8TqT%2BaPio07UddCz7Tg%40mail.gmail.com%3E http://mail-archives.apache.org/mod_mbox/httpd-dev/201111.mb... https://github.com/apache/httpd/blob/trunk/server/util_time.c#L310-L327 https://github.com/apache/httpd/blob/trunk/server/util_time.... The internals of glibc can often be pretty surprising sometimes, I'd really encourage people to go spelunking into the glibc source when they are profiling applications.