Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-Q8

[Rusty Russell]

On Thu, 2004-09-02 at 17:46, Ingo Molnar wrote:
> Rusty, what's going on in this code?

Good question!  Not my code, fortunately...

> #1: we kmalloc(GFP_KERNEL) with a spinlock held and softirqs off - ouch!
> 
> #2: why does it do the kmalloc() anyway? It could store the position in
>     the seq pointer just fine. No need to alloc an integer pointer to
>     store the value in ...
> 
> #3: to fix the latency, ct_seq_show() could take the ip_conntrack_lock 
>     and could check the current index against ip_conntrack_htable_size. 
>     There's not much point in making this non-preemptible, there's 
>     a 4K granularity anyway.

The code tries to put an entire hash bucket into a single seq_read(). 
That's not going to work if the hash is really deep.  On the other hand,
not much will, and it's simple.

The lock is only needed on traversing: htable_size can't change after
init anyway, so it should be done in ct_seq_show.

Fix should be fairly simple...
Rusty.
-- 
Anyone who quotes me in their signature is an idiot -- Rusty Russell

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