On 09/27/2012 04:27 PM, Gregory Farnum wrote:
On Thu, Sep 27, 2012 at 3:23 PM, Jim Schutt<jaschut@xxxxxxxxxx> wrote:
On 09/27/2012 04:07 PM, Gregory Farnum wrote:
Have you tested that this does what you want? If it does, I think
we'll want to implement this so that we actually release the memory,
but continue accounting it.
Yes. I have diagnostic patches where I add an "advisory" option
to Throttle, and apply it in advisory mode to the cluster throttler.
In advisory mode Throttle counts bytes but never throttles.
Can't you also do this if you just set up a throttler with a limit of 0? :)
Hmmm, I expect so. I guess I just didn't think of doing it that way....
When I run all the clients I can muster (222) against a relatively
small number of OSDs (48-96), with osd_client_message_size_cap set
to 10,000,000 bytes I see spikes of> 100,000,000 bytes tied up
in ops that came through the cluster messenger, and I see long
wait times (> 60 secs) on ops coming through the client throttler.
With this patch applied, I can raise osd_client_message_size_cap
to 40,000,000 bytes, but I rarely see more than 80,000,000 bytes
tied up in ops that came through the cluster messenger. Wait times
for ops coming through the client policy throttler are lower,
overall daemon memory usage is lower, but throughput is the same.
Overall, with this patch applied, my storage cluster "feels" much
less brittle when overloaded.
Okay, cool. Are you interested in reducing the memory usage a little
more by deallocating the memory separately from accounting it?
My testing doesn't indicate a need -- even keeping the memory
around until the op is done, my daemons use less memory overall
to get the same throughput. So, unless some other load condition
indicates a need, I'd counsel simplicity.
-- Jim
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