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From: "Laatz, Kevin" <kevin.laatz@intel.com>
To: "Björn Töpel" <bjorn.topel@gmail.com>
Cc: Netdev <netdev@vger.kernel.org>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Björn Töpel" <bjorn.topel@intel.com>,
	"Karlsson, Magnus" <magnus.karlsson@intel.com>,
	"Jonathan Lemon" <jonathan.lemon@gmail.com>,
	"Bruce Richardson" <bruce.richardson@intel.com>,
	ciara.loftus@intel.com, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next] libbpf: add xsk_umem__adjust_offset
Date: Fri, 13 Sep 2019 11:21:16 +0100	[thread overview]
Message-ID: <847dcd1e-81ba-4364-7242-d280a17f9244@intel.com> (raw)
In-Reply-To: <CAJ+HfNgQY6muwzGgBW6xLFzKeiCMQUwrz_yrywB3F_VSKbaadQ@mail.gmail.com>

On 13/09/2019 05:59, Björn Töpel wrote:
> On Thu, 12 Sep 2019 at 17:47, Kevin Laatz <kevin.laatz@intel.com> wrote:
>> Currently, xsk_umem_adjust_offset exists as a kernel internal function.
>> This patch adds xsk_umem__adjust_offset to libbpf so that it can be used
>> from userspace. This will take the responsibility of properly storing the
>> offset away from the application, making it less error prone.
>>
>> Since xsk_umem__adjust_offset is called on a per-packet basis, we need to
>> inline the function to avoid any performance regressions.  In order to
>> inline xsk_umem__adjust_offset, we need to add it to xsk.h. Unfortunately
>> this means that we can't dereference the xsk_umem_config struct directly
>> since it is defined only in xsk.c. We therefore add an extra API to return
>> the flags field to the user from the structure, and have the inline
>> function use this flags field directly.
>>
> Can you expand this to a series, with an additional patch where these
> functions are used in XDP socket sample application, so it's more
> clear for users?

These functions are currently not required in the xdpsock application and I think forcing them in would be messy :-). However, an example of the use of these functions could be seen in the DPDK AF_XDP PMD. There is a patch herehttp://patches.dpdk.org/patch/58624/  where we currently do the offset adjustment to the handle manually, but with this patch we could replace it with xsk_umem__adjust_offset and have a real use example of the functions being used.

Would this be enough for an example?

Thanks,
Kevin


  reply	other threads:[~2019-09-13 10:21 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-12  7:28 [PATCH bpf-next] libbpf: add xsk_umem__adjust_offset Kevin Laatz
2019-09-13  4:59 ` Björn Töpel
2019-09-13 10:21   ` Laatz, Kevin [this message]
2019-09-13 11:17     ` Björn Töpel
2019-09-13 22:49 ` Yonghong Song

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