netdev - Re: [PATCH] net/packet: simply allocations in alloc_one_pg_vec

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Date:   Sat, 16 May 2020 16:59:21 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     David Miller <davem@...emloft.net>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net/packet: simply allocations in alloc_one_pg_vec_page

On Sat, May 16, 2020 at 4:39 PM David Miller <davem@...emloft.net> wrote:
>
> From: Shakeel Butt <shakeelb@...gle.com>
> Date: Sat, 16 May 2020 15:35:46 -0700
>
> > So, my argument is if non-zero order vzalloc has failed (allocations
> > internal to vzalloc, including virtual mapping allocation and page
> > table allocations, are order 0 and use GFP_KERNEL i.e. triggering
> > reclaim and oom-killer) then the next non-zero order page allocation
> > has very low chance of succeeding.
>
> Also not true.
>
> Page table allocation strategies and limits vary by architecture, they
> may even need virtual mappings themselves.  So they can fail in situations
> where a non-zero GFP_KERNEL page allocator allocation would succeed.

Thanks for the explanation. Do you think calling vzalloc only for
non-zero order here has any value?