Date: Thu, 26 Apr 2018 11:02:58 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Ryan Stone <rysto32@gmail.com> Cc: FreeBSD Current <current@freebsd.org>, menyy@mellanox.com, FreeBSD Net <net@freebsd.org> Subject: Re: mlx5(4) jumbo receive Message-ID: <20180426080258.GI6887@kib.kiev.ua> In-Reply-To: <CAFMmRNwKXCxGbz7zmOsiCMWbY3%2BrBzGwJJo_HHkAbbhEz2UfLQ@mail.gmail.com> References: <20180424085553.GA6887@kib.kiev.ua> <CAFMmRNwKXCxGbz7zmOsiCMWbY3%2BrBzGwJJo_HHkAbbhEz2UfLQ@mail.gmail.com>
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On Wed, Apr 25, 2018 at 04:04:13PM -0400, Ryan Stone wrote: > On Tue, Apr 24, 2018 at 4:55 AM, Konstantin Belousov > <kostikbel@gmail.com> wrote: > > +#ifndef MLX5E_MAX_RX_BYTES > > +#define MLX5E_MAX_RX_BYTES MCLBYTES > > +#endif > > Why do you use a 2KB buffer rather than a PAGE_SIZE'd buffer? > MJUMPAGESIZE should offer significantly better performance for jumbo > frames without increasing the risk of memory fragmentation. Part of the answer is that the patch was not written in one go (even not by one person), but evolved, and this is how it shaped. Another part is that indeed, as Rick stated, I am not sure about mixing the different sizes for mbuf allocator. This might be more FUD than factual-based considerations, but still. I believe that the patch as is provides the important improvements. If developing mlx4(4) change of the same nature, I will probably take this into the exp stage from the beginning. For mlx5(4), I think that the patch should be applied as is, then I might experiment with PAGE_SIZE as the later step.
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