linux-kernel - Re: [RFC][PATCH][NET] Fix never pruned tcp out-of-order queue

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Date:	Tue, 15 Apr 2008 13:33:47 +0400
From:	Vitaliy Gusev <vgusev@...nvz.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	David Miller <davem@...emloft.net>, kuznet@....inr.ac.ru,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH][NET] Fix never pruned tcp out-of-order queue

On 15 April 2008 12:30:34 Andi Kleen wrote:
> Vitaliy Gusev wrote:
> > On 15 April 2008 12:18:10 David Miller wrote:
> >> From: Andi Kleen <andi@...stfloor.org>
> >> Date: Tue, 15 Apr 2008 10:14:56 +0200
> >>
> >>> The main difference seems to be that
> >>> sk_rmem_schedule/__sk_mem_schedule is called more often, but it is 
> >>> unclear how this affects the ooo pruning which only checks
> >>> the queue length anyways.
> >> tcp_data_queue() would not do the tcp_prune_ofo_queue() in some
> >> cases, it's the whole point of the patch.
> 
> I still think the guards are pretty much the same as before, sorry:)
> 
> > Yes, if second sk_rmem_schedule() failed then tcp_prune_ofo_queue() is force called
> > and try sk_rmem_schedule() again.
> 
> Yes but that doesn't affect the ooo prune guards at all, they only check
> rmem_alloc and neither sk_rmem_schedule() nor __sk_mem_schedule
> change that. Also the two callers are the same too in their checks.
>
> But why not repeat the whole prune for all cases in this case then?
> 
> e.g. you should probably at least repeat the third step (setting
> pred_flags to 0) too.

Did you mean merely add check on tcp_memory_allocated < prot->sysctl_mem[2]
to tcp_prune_queue() ?
It is not enough as __sk_mem_schedule() can fail also
because of memory_pressure is on and there are too many opened sockets.

i.e. I avoid duplicating checks from __sk_mem_schedule().


> 
> -Andi



-- 
Thank,
Vitaliy Gusev
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