netdev - Re: order 7 allocations from xt

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Date:	Thu, 03 Jan 2013 10:00:46 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Dave Jones <davej@...hat.com>
Cc:	netdev@...r.kernel.org, h.reindl@...lounge.net,
	Fedora Kernel Team <kernel-team@...oraproject.org>
Subject: Re: order 7 allocations from xt_recent

On Thu, 2013-01-03 at 12:26 -0500, Dave Jones wrote:
> On Thu, Jan 03, 2013 at 12:11:15PM -0500, Dave Jones wrote:
>  > On Thu, Jan 03, 2013 at 08:55:04AM -0800, Eric Dumazet wrote:
>  >  > On Thu, 2013-01-03 at 11:43 -0500, Dave Jones wrote:
>  >  > > We had a report from a user that shows this code trying
>  >  > > to do enormous allocations, which isn't going to work too well..
>  >  > >  ...
>  >  > > Which is initialised thus..
>  >  > > 
>  >  > >         ip_list_hash_size = 1 << fls(ip_list_tot);
>  >  > > 
>  >  > > And ip_list_tot is 10000 in this case. Hmm ?
>  >  > > 
>  >  > > Complete report and setup described in his bug report at https://bugzilla.redhat.com/show_bug.cgi?id=890715
>  >  > 
>  >  > Yes, we had a report and a patch :
>  >  > 
>  >  > http://comments.gmane.org/gmane.linux.network/248216
>  >  > 
>  >  > I'll send it in a more formal way.
>  > 
>  > Ah! Excellent.
>  > 
>  > That 'check size and vmalloc/kmalloc accordingly' thing seems to be a pattern
>  > that comes up time and time again.  Is it worth maybe making a more generic
>  > version of that instead of open-coding it each time it comes up ?
> 
> Something else that I'm puzzled by.
> 
> In the report above, it failed to allocate 512kb, but..
> 
> Node 0 Normal: 2388*4kB 347*8kB 1029*16kB 3512*32kB 29*64kB 2*128kB 1*256kB 5*512kB 1*1024kB 0*2048kB 0*4096kB = 147128kB
>                                                                             ^^^^^^^^^^^^^^^^
> 
> Shouldn't the allocator have been able to satisfy that anyway ?
> 
> 	Dave
> 

Might be something related to the CONFIG_COMPACTION=y and lumpy reclaim
removal ?

Anyway, we keep a fraction of memory for ATOMIC allocations.





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