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HEADS UP Re: slapd lightweight dispatcher
Howard Chu wrote:
Quanah Gibson-Mount wrote:
Given our positive results from eliminating the connections_mutex I'm
going to be stripping out all of the multi-conn stuff from HEAD.
I've done a lot of testing in the last several days on a binary with
the lightweight dispatcher code enabled (2.3 base), and I just want
to say I'm a very big fan of it. It allows slapd to scale under high
load at a rate I've not previously seen. I've also played with the
multi-conn flag as well, and haven't seen it particularly affect the
rates when only it is enabled, but I haven't tried the lightweight
dispatcher without it being enabled at the same time.The multi-conn code definitely needs more attention, it breaks the
Win32 build in its current state.
One thing I'll note about multi-conn is that it requires a variable
in connection.c to be set to the number of cpu's on the system where
slapd will be run. I think this should instead be changed to a
parameter in slapd.conf (slapd-cpus ??) so one doesn't have to have
fixed slapd's for given systems. That same parameter could be used
for giving guidelines to slapadd/slapdindex as well, and the
tool-threads parameter could be replaced by the new one.
Along those lines, in the normal (non-Win32) case I don't see an
actual need for the connections_mutex. Since we go directly from
descriptor number to connection slot, there's really no shared
resource to protect that isn't already protected by the conn->c_mutex.
I think the Win32 code will still need the connections_mutex. For Win32
performance I may consider keeping its descriptor table sorted so we can
do binary search on it, but that'll come later. Too bad there's not a
simple way to hash those things; apparently a Winsock descriptor is an
offset into a system-wide table, not per-process. If a simple solution
presents itself, we can eliminate the search here too.
-- Howard Chu
Chief Architect, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc
OpenLDAP Core Team http://www.openldap.org/project/