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From: Daniel Borkmann <daniel@iogearbox.net>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Lorenzo Bianconi <lorenzo@kernel.org>,
	bpf@vger.kernel.org, netdev@vger.kernel.org, davem@davemloft.net,
	kuba@kernel.org, ast@kernel.org, toshiaki.makita1@gmail.com,
	lorenzo.bianconi@redhat.com, toke@redhat.com,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v3 bpf-next] net: veth: alloc skb in bulk for ndo_xdp_xmit
Date: Thu, 4 Feb 2021 16:43:10 +0100	[thread overview]
Message-ID: <65a218bc-3ebf-001e-174d-b67817c83b45@iogearbox.net> (raw)
In-Reply-To: <20210204100556.59459549@carbon.lan>

On 2/4/21 10:05 AM, Jesper Dangaard Brouer wrote:
[...]
> It was Andrew (AKPM) that wanted the API to either return the requested
> number of objects or fail. I respected the MM-maintainers request at
> that point, even-though I wanted the other API as there is a small
> performance advantage (not crossing page boundary in SLUB).
> 
> At that time we discussed it on MM-list, and I see his/the point:
> If API can allocate less objs than requested, then think about how this
> complicated the surrounding code. E.g. in this specific code we already
> have VETH_XDP_BATCH(16) xdp_frame objects, which we need to get 16 SKB
> objects for.  What should the code do if it cannot get 16 SKBs(?).

Right, I mentioned the error handling complications above wrt < n_skb case. I think iff this
ever gets implemented and there's a need, it would probably be best to add a new flag like
__GFP_BULK_BEST_EFFORT to indicate that it would be okay to return x elements with x being
in (0, size], so that only those callers need to deal with this, and all others can expect
[as today] that != 0 means all #size elements were bulk alloc'ed.

Thanks,
Daniel

      reply	other threads:[~2021-02-04 15:44 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-29 22:04 Lorenzo Bianconi
2021-01-31 14:16 ` Toshiaki Makita
2021-02-02 14:14 ` Jesper Dangaard Brouer
2021-02-04  0:10 ` patchwork-bot+netdevbpf
2021-02-04  0:14 ` Daniel Borkmann
2021-02-04  9:05   ` Jesper Dangaard Brouer
2021-02-04 15:43     ` Daniel Borkmann [this message]

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