netdev - Re: [PATCH 1/2] r8169: allocate with GFP

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Message-ID: <20101008160341.GC10393@redhat.com>
Date:	Fri, 8 Oct 2010 18:03:42 +0200
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Francois Romieu <romieu@...zoreil.com>, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] r8169: allocate with GFP_KERNEL flag when able to
 sleep

On Fri, Oct 08, 2010 at 05:04:07PM +0200, Eric Dumazet wrote:
> Le vendredi 08 octobre 2010 à 16:52 +0200, Stanislaw Gruszka a écrit :
> > On Fri, Oct 08, 2010 at 04:25:00PM +0200, Stanislaw Gruszka wrote:
> > > We have fedora bug report where driver fail to initialize after
> > > suspend/resume because of memory allocation errors:
> > > https://bugzilla.redhat.com/show_bug.cgi?id=629158
> > 
> > There is also one more thing to do regarding above. Calltraces from bug
> > reports, shows that order 3 allocation fail. On arch with 4kB pages,
> > order 3 mean 32kB allocation. We want to alloc 16kB, but there is also
> > internal sk_buff data what make that we exceed the boundary and take
> > 32kB from allocator, getting almost 50% wastage.
> > 
> 
> Or its only an 1460+overhead allocation, and SLUB uses order-3 pages to
> satisfy 2048 bytes allocations.

Rather not, trace show failure in rtl8169_rx_fill, where we allocate rx
buffers and these are 16kB big by default.

> Switch to SLAB -> no more problem ;)

yeh, I wish to, but fedora use SLUB because of some debugging
capabilities. 

> > To fix we can use similar method as in niu or iwlwifi drivers, alloc
> > pages directly form buddy allocator and attach them to skb (by
> > skb_add_rx_frag for example). I'm going to prepare such patch, but
> > I have one doubt, what happens if page size in system is bigger
> > than 16kB, should I care about such case? 
> 
> Seems tricky. Should we patch all drivers to do something like that ?

I think, only on these drivers which do alloc_skb(n*PAGE_SIZE).
As alternative we can be smarter in alloc_skb.

Stanislaw
> 
> 
> 
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