On Apr 7, 2007, at 12:30, Timo Sirainen wrote:
Although Dovecot is already read-lockless and it uses only short-
lived write locks, it's be really nice to just get rid of the
locking completely. :)
I just figured out that O_APPEND is pretty great. If the operating
system updates seek position after writing to a file opened with
O_APPEND, writes to Dovecot's transaction log file can be made
lockless. I see that this works with Linux and Solaris, but not
with OS X. Could you BSD people try if it works there? http://
dovecot.org/tmp/append.c and see if it says "offset = 0" (bad) or
non-zero (yay). The O_APPEND at least doesn't work with NFS, so
it'll have to be optional anyway.
I tested on Mac OS X. Works on Intel (offset = 5), but not PowerPC
(offset = 0)... Both are running 10.4.9.
Kernel versions:
Darwin Kernel Version 8.9.0: Thu Feb 22 20:54:07 PST 2007;
root:xnu-792.17.14~1/RELEASE_PPC
Darwin Kernel Version 8.9.1: Thu Feb 22 20:55:00 PST 2007;
root:xnu-792.18.15~1/RELEASE_I386
-jim
