Re: BUG: Slowdown on 3000 socket-machines tracked down

From: Ben Greear
Date: Thu Mar 10 2005 - 14:26:01 EST

Andi Kleen wrote:

If he had a lot of RX traffic (it is hard to figure out because his
bug reports are more or less useless and mostly consists of rants):
The packets are allocated with GFP_ATOMIC and a lot of traffic
overwhelms the free memory.

Some drivers work around this by doing the RX ring refill in process
context (easier with NAPI), but not all do.

I think his traffic is mostly 'send' from his server's perspective.

He's reading from disk with sendfile too, I believe, so maybe that
would be consuming lots of pages of memory?

However, in my case, I would definately welcome something that auto-tuned
the VM to give me lots and lots of GFP_ATOMIC pages. As it is now, I
end up setting the /proc/sys/vm/freepages much higher. Since it appears
the name has changed and I didn't notice, I guess my script to set
this has not actually been doing anything useful in the 2.6 kernel series :P

Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc

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