On May 10, 2007, at 14:58 , Steve Grimm wrote:
On 5/10/07 11:09 AM, "Dustin Sallings" <[EMAIL PROTECTED]> wrote:
No, I don't wait, but with a single connection to memcached
(where "single"
may be substituted with a small number), requests naturally stack
up and can
be merged. Write buffers can pull from all queued events.
Reducing the
number of packets moved around the network for requests would seem
like it
should increase performance.
Yes, absolutely it will, both from a server CPU point of view
(multi-get is
much more efficient than get) and, if you're really pushing a lot of
traffic, from a network capacity point of view. So you're saying the
batching only happens when the socket buffer on your memcached
connection is
full and you have to hang on to data and wait for the connection to
become
writeable again anyway? That makes sense. (Yes, sorry, I know I
could just
go look at the code...)
Right. I'm a bit lazier in this than I could be (partially because
buffers in java are...weird), but effectively, the IO thread
maintains its own write buffer that it fills from buffers from other
operations. There's a special case in the fill method that merges
sequential gets.
Even without the get merging, multiple requests to the same server
may be sent in the same packet.
I think it isn't something we ever considered because the ratio of
number of
memcached hosts to number of client processes on any single client
machine
here is pretty high; the chances of enough separate client
processes on one
host needing to write enough requests to the same memcached host at
the same
time to clog up a connection are pretty slim. But if your number of
clients
per host is much higher than your number of memcached servers, then
that
wouldn't be so true.
This makes sense. In a java app server context like mine, I'd get
very little benefit from such a thing because I'm already able to
share the connection resource very effectively. I'm thinking more
about the cases where people aren't able to.
You seem to have your farm well under control.
It's interesting that you tried this. Do you still have the proxy
application available? It may be a good starting point for my
experiments,
and it may not be as optimal as what I'm thinking.
We do still have it, and the plan from the start was to release it
as open
source at some point. Since it ended up being less useful than we
thought it
would be, I didn't finish the prep work for that. It still needs a
bit of
cleaning up (not to mention documentation) before I'd be comfortable
unleashing it on the world. If people are really interested I'll
see what I
can do, but don't expect it tomorrow or anything.
Well, don't worry about the state of it too much, but take your
time. I'm not in a huge hurry to take on more work now anyway.
--
Dustin Sallings
