Date: Wed, 25 Apr 2018 22:21:43 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: Ryan Stone <rysto32@gmail.com>, Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Current <current@freebsd.org>, "menny@mellanox.com" <menny@mellanox.com>, FreeBSD Net <net@freebsd.org> Subject: Re: mlx5(4) jumbo receive Message-ID: <YQBPR0101MB104231911340A77D6DDC360EDD8F0@YQBPR0101MB1042.CANPRD01.PROD.OUTLOOK.COM> 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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Ryan Stone wrote:
>On Tue, Apr 24, 2018 at 4:55 AM, Konstantin Belousov >><kostikbel@gmail.co=
m>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.
Actually, when I was playing with using jumbo mbuf clusters for NFS, I was =
able
to get it to fragment to the point where allocations failed when mixing 2K =
and
4K mbuf clusters.
Admittedly I was using a 256Mbyte i386 and it wasn't easily reproduced, but
it was possible.
--> Using a mix of 2K and 4K mbuf clusters can result in fragmentation, alt=
hough
I suspect that it isn't nearly as serious as what can happen when usi=
ng 9K
mbuf clusters.
rick=
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