Re: cmp(1) has a bottleneck, but where?
Adrian Chadd <[email protected]>
| Newsgroups | gmane.os.freebsd.performance |
|---|---|
| Message-ID | <CAJ-Vmo=JL8Kqu2uw-t1eKWUhdZx6CgP+PSiGgt91WV9WAs3idg@mail.gmail.com> |
On 3 January 2012 00:34, Marc Olzheim <[email protected]> wrote: > On Tue, Jan 03, 2012 at 12:21:10AM -0800, Garrett Cooper wrote: >> The file is 3.0GB in size. Look at all those page faults though! >> Thanks! >> -Garrett > > From usr.bin/cmp/c_regular.c: > > #define MMAP_CHUNK (8*1024*1024) > ... > for (..) { > mmap() chunk of size MMAP_CHUNK. > compare > munmap()k > } > > That 8 MB chunk size sounds like a bad plan to me. I can imagine > something needed to be done to compare files larger than X GB on a 32bit > system, but 8MB is pretty small... Er, hint: look at the average IO size in the cmp versus cp stats above? Something/somehow it's issuing smaller IOs when using mmap? Adrian _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "[email protected]"