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Date:      Fri, 21 Nov 2014 09:05:17 +0000
From:      "Robert N. M. Watson" <rwatson@FreeBSD.org>
To:        Marko Zec <zec@fer.hr>
Cc:        Craig Rodrigues <rodrigc@freebsd.org>, FreeBSD Net <freebsd-net@freebsd.org>, "Bjoern A.Zeeb" <bz@freebsd.org>
Subject:   Re: VIMAGE UDP memory leak fix
Message-ID:  <36975BCB-1F45-4128-9FB6-004F07489E53@FreeBSD.org>
In-Reply-To: <20141121095847.11601640@x23>
References:  <CAG=rPVehky00X4MuQQ-_Oe5ezWg52ZZrPASAh9GBy7baYv78CA@mail.gmail.com> <20141121002937.4f82daea@x23> <A4D676B3-6C50-47F7-8CFD-50B44FF4BE98@FreeBSD.org> <20141121095847.11601640@x23>

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On 21 Nov 2014, at 08:58, Marko Zec <zec@fer.hr> wrote:

> Nevertheless, I'd prefer most of network stack UMA zones to be
> de-virtualized, at least those which cannot cause interference between
> VNETs, and that excludes syncache, reassembly, hostcache and the =
likes.
> De-virtualization doesn't require touching the UMA_ZONE_NOFREE flag, =
so
> doesn't affect non-VIMAGE builds.  Any objections to that approach?

To my mind, the only real concern is whether or not you lose access to =
resource allocation limits that would previously have been present. On =
the whole, we've tried to centralise resource limitations on kernel =
memory allocation in UMA, and it would be great if we could find a nice =
approach to implementing both per-vimage and per-system allocation =
limits. One thing I'd pondered in the past was whether we could move to =
a single zone, with its own limits/etc, but also the ability to pass an =
optional uma_resourcepool_t that allowed additional limits to be imposed =
based on some other criteria -- e.g., vimage membership. That strikes me =
as a somewhat complex proposal that would bring new =
performance/synchronisation concerns, so isn't necessarily something to =
act on. However, the upshot is that, although I do not oppose combining =
the zones, we should be aware that we're eliminating a form of resource =
partitioning between vimages that we may want to find some other =
solution for (ideally, an elegant one).

Robert=



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