netdev - Re: [RFC] net/core/dst.c : Should'nt dst_run_gc() be more scalable and friendly ?

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Message-ID: <20070817081522.GA16720@gondor.apana.org.au>
Date:	Fri, 17 Aug 2007 16:15:22 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC] net/core/dst.c : Should'nt dst_run_gc() be more scalable and friendly ?

On Fri, Aug 17, 2007 at 10:10:30AM +0200, Eric Dumazet wrote:
>
> Will a workqueue react the same in case of a DDOS situation, 
> where softirq could use all CPU cycles to handle incoming
> packets and feed the GC list, and GC would never
> have a chance to scan and free some items ?

Well when that happens the softirqs will be deferred to
ksoftirqd which should share the CPU fairly with the
workqueue.

> About chunk processing, I did it on purpose, to not throw away
> all CPU cache. Goal is to process entries, but not all of them
> in a row, especially if we find many yet referenced entries
> (and thus not candidates to freeing)

I agree that chunks are desirable for a timer since you'd
be hogging the CPU otherwise.  However, if you went to a
workqueue then it's less of a concern and would simplify
things.  In particular, you won't have to pick a good
chunk size :)

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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