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Date:      Tue, 19 May 2020 23:47:10 +0200
From:      "Kristof Provost" <kp@FreeBSD.org>
To:        "Andrew Gallatin" <gallatin@cs.duke.edu>
Cc:        "Eric Joyner" <erj@FreeBSD.org>, "Jacob Keller" <jacob.e.keller@intel.com>, shurd@FreeBSD.org, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r347418 - head/sys/net
Message-ID:  <CE8E8A09-00DA-4496-B3A8-E7BFA83ECFBC@FreeBSD.org>
In-Reply-To: <c954afea-b96d-a2c3-7037-4a419d23be86@cs.duke.edu>
References:  <201905100041.x4A0fhNT083122@repo.freebsd.org> <3BBFB371-EA44-4EE9-8A55-542CDE273CC4@FreeBSD.org> <c954afea-b96d-a2c3-7037-4a419d23be86@cs.duke.edu>

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On 19 May 2020, at 17:02, Andrew Gallatin wrote:
> On 2020-05-19 04:21, Kristof Provost wrote:
>
>> The if_bnxt driver initialises |.isc_nrxd_max = {INT32_MAX, 
>> INT32_MAX, INT32_MAX},|, so presumably that’s the cause.
>> I don’t know what a sane value would be though. I’ve defaulted to 
>> 4096 (because that’s what some other iflib users seems to do) for 
>> now, and that seems to work. It doesn’t panic and I can get traffic 
>> through it at least:
>
> You seem to be setting the max, not the default, and 4K max 
> descriptors on a 100g device is going to basically cripple it.
>
Yeah, I just grabbed whatever number other iflib users used. My 
immediate concern was to get it to stop panicking.

> How about setting to the next power of 2 below max int so as to keep 
> with the authors intent?
>
Makes sense, yes.

> If we don't already have a macro, something like  (INT32_MAX >> 1) + 1
>
https://reviews.freebsd.org/D24922

Best regards,
Kristof



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