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Date:   Wed, 5 Dec 2018 16:17:31 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To:     Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     Felix Fietkau <nbd@nbd.name>,
        linux-wireless <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH 2/2] mt76: dma: add rx buffer recycle support
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> On Wed, Dec 05, 2018 at 11:37:33AM +0100, Lorenzo Bianconi wrote:
> > >
> > > Add support for recycling rx buffers if they are not forwarded
> > > to network stack instead of reallocate them from scratch
> > >
> > > Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
> > > ---
> > 
> > Felix,
> > 
> > could you please drop this patch since it does not help to reduce pressure
> > on page_frag_cache.
> 
> What is the problem ? Maybe using kmalloc() instead of page_frag_alloc()
> could help (kmalloc has standard kmem_cache for 2048 bytes object) ?

Hi Stanislaw,

I think the only difference in using a recycle buffer with page_frag_cache is
we are a little bit less greedy in consuming the compound page since in case of
error we will reuse the previously allocated fragment. However we will need to
reallocate a new compound page if we have a leftover fragment that 'locks'
the previous compound (we have the same issue if we do not use the recycle
buffer). Does this 'little' improvement worth a more complex code?
Do you agree or is there something I am missing here?

Regards,
Lorenzo

> 
> Thanks
> Stanislaw