netdev - Re: [PATCH v4 net-next 1/5] net: xdp: introduce bulking for xdp tx return path

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Message-ID: <20201110115313.6654141b@carbon>
Date:   Tue, 10 Nov 2020 11:53:12 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        lorenzo.bianconi@...hat.com, davem@...emloft.net, kuba@...nel.org,
        ilias.apalodimas@...aro.org, brouer@...hat.com
Subject: Re: [PATCH v4 net-next 1/5] net: xdp: introduce bulking for xdp tx
 return path

On Fri,  6 Nov 2020 19:19:07 +0100
Lorenzo Bianconi <lorenzo@...nel.org> wrote:

> XDP bulk APIs introduce a defer/flush mechanism to return
> pages belonging to the same xdp_mem_allocator object
> (identified via the mem.id field) in bulk to optimize
> I-cache and D-cache since xdp_return_frame is usually run
> inside the driver NAPI tx completion loop.
> The bulk queue size is set to 16 to be aligned to how
> XDP_REDIRECT bulking works. The bulk is flushed when
> it is full or when mem.id changes.
> xdp_frame_bulk is usually stored/allocated on the function
> call-stack to avoid locking penalties.
> Current implementation considers only page_pool memory model.
> 
> Suggested-by: Jesper Dangaard Brouer <brouer@...hat.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
>  include/net/xdp.h | 11 ++++++++-
>  net/core/xdp.c    | 61 +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 71 insertions(+), 1 deletion(-)

I have a number of optimization improvements to this patch.  Mostly
related to simple likely/unlikely compiler annotations, that give
better code layout for I-cache benefit.  Details in[1]. (Lorenzo is informed)

[1] https://github.com/xdp-project/xdp-project/blob/master/areas/mem/xdp_bulk_return01.org
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer