netdev - Re: [net-next PATCH 0/7] net: bulk alloc side and more bulk free drivers

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Message-ID: <20160304163641.GA52086@ast-mbp.thefacebook.com>
Date:	Fri, 4 Mar 2016 08:36:44 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	eugenia@...lanox.com, Alexander Duyck <alexander.duyck@...il.com>,
	saeedm@...lanox.com, gerlitz.or@...il.com
Subject: Re: [net-next PATCH 0/7] net: bulk alloc side and more bulk free
 drivers

On Fri, Mar 04, 2016 at 02:01:14PM +0100, Jesper Dangaard Brouer wrote:
> This patchset use the bulk ALLOC side of the kmem_cache bulk APIs, for
> SKB allocations.  The bulk free side got enabled in merge commit
> 3134b9f019f2 ("net: mitigating kmem_cache free slowpath").
> 
> The first two patches is a followup on the free-side, which enables
> bulk-free in the drivers mlx4 and mlx5 (dev_kfree_skb -> napi_consume_skb).
> 
> Rest of patchset is focused on bulk alloc-side.  We start with a
> conservative bulk alloc of 8 SKB, which all drivers using the
> napi_alloc_skb() call will benefit from.  Then the API is extended to,
> allow driver hinting on needed SKBs (only some drivers know this
> size), and mlx5 driver is the first user of hinting.

patches 1-5 look very good to me. Should help all cases afaik.
As far as 6-7 about hints I have a question. Does this hint
actually makes the difference? The fixed bulk alloc of 8 probably
easier for the main slub, but when mlx5 starts doing 'work_done' as
a hint there will be more 'random' bulking going on.
Was wondering whether you have the perf numbers to back up 6/7