Date: Thu, 23 Feb 2012 09:19:13 +0100 From: Fabien Thomas <fabien.thomas@netasq.com> To: Jack Vogel <jfvogel@gmail.com> Cc: Ben Hutchings <bhutchings@solarflare.com>, FreeBSD Net <freebsd-net@freebsd.org>, Luigi Rizzo <rizzo@iet.unipi.it>, re <re@freebsd.org>, FreeBSD stable <freebsd-stable@freebsd.org> Subject: Re: nmbclusters: how do we want to fix this for 8.3 ? Message-ID: <134564BB-676B-49BB-8BDA-6B8EB8965969@netasq.com> In-Reply-To: <CAFOYbc=BWkvGuqAOVehaYEVc7R_4b1Cq1i7Ged=-YEpCekNvfA@mail.gmail.com> References: <CAFOYbc=oU5DxZDZQZZe4wJhVDoP=ocVOnpDq7bT=HbVkAjffLQ@mail.gmail.com> <20120222205231.GA81949@onelab2.iet.unipi.it> <1329944986.2621.46.camel@bwh-desktop> <20120222214433.GA82582@onelab2.iet.unipi.it> <CAFOYbc=BWkvGuqAOVehaYEVc7R_4b1Cq1i7Ged=-YEpCekNvfA@mail.gmail.com>
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--Apple-Mail=_D789DF06-0C84-453C-AD51-1C13DBE43289 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 Le 22 f=E9vr. 2012 =E0 22:51, Jack Vogel a =E9crit : > On Wed, Feb 22, 2012 at 1:44 PM, Luigi Rizzo <rizzo@iet.unipi.it> = wrote: >=20 >> On Wed, Feb 22, 2012 at 09:09:46PM +0000, Ben Hutchings wrote: >>> On Wed, 2012-02-22 at 21:52 +0100, Luigi Rizzo wrote: >> ... >>>> I have hit this problem recently, too. >>>> Maybe the issue mostly/only exists on 32-bit systems. >>>=20 >>> No, we kept hitting mbuf pool limits on 64-bit systems when we = started >>> working on FreeBSD support. >>=20 >> ok never mind then, the mechanism would be the same, though >> the limits (especially VM_LIMIT) would be different. >>=20 >>>> Here is a possible approach: >>>>=20 >>>> 1. nmbclusters consume the kernel virtual address space so there >>>> must be some upper limit, say >>>>=20 >>>> VM_LIMIT =3D 256000 (translates to 512MB of address space) >>>>=20 >>>> 2. also you don't want the clusters to take up too much of the >> available >>>> memory. This one would only trigger for minimal-memory systems, >>>> or virtual machines, but still... >>>>=20 >>>> MEM_LIMIT =3D (physical_ram / 2) / 2048 >>>>=20 >>>> 3. one may try to set a suitably large, desirable number of buffers >>>>=20 >>>> TARGET_CLUSTERS =3D 128000 >>>>=20 >>>> 4. and finally we could use the current default as the absolute = minimum >>>>=20 >>>> MIN_CLUSTERS =3D 1024 + maxusers*64 >>>>=20 >>>> Then at boot the system could say >>>>=20 >>>> nmbclusters =3D min(TARGET_CLUSTERS, VM_LIMIT, MEM_LIMIT) >>>>=20 >>>> nmbclusters =3D max(nmbclusters, MIN_CLUSTERS) >>>>=20 >>>>=20 >>>> In turn, i believe interfaces should do their part and by default >>>> never try to allocate more than a fraction of the total number >>>> of buffers, >>>=20 >>> Well what fraction should that be? It surely depends on how many >>> interfaces are in the system and how many queues the other = interfaces >>> have. >>=20 >>>> if necessary reducing the number of active queues. >>>=20 >>> So now I have too few queues on my interface even after I increase = the >>> limit. >>>=20 >>> There ought to be a standard way to configure numbers of queues and >>> default queue lengths. >>=20 >> Jack raised the problem that there is a poorly chosen default for >> nmbclusters, causing one interface to consume all the buffers. >> If the user explicitly overrides the value then >> the number of cluster should be what the user asks (memory = permitting). >> The next step is on devices: if there are no overrides, the default >> for a driver is to be lean. I would say that topping the request = between >> 1/4 and 1/8 of the total buffers is surely better than the current >> situation. Of course if there is an explicit override, then use >> it whatever happens to the others. >>=20 >> cheers >> luigi >>=20 >=20 > Hmmm, well, I could make the default use only 1 queue or something = like > that, > was thinking more of what actual users of the hardware would want. >=20 I think this is more reasonable to setup interface with one queue. Even if the cluster does not hit the max you will end up with unbalanced = setting that let very low mbuf count for other uses. > After the installed kernel is booted and the admin would do whatever = post > install > modifications they wish it could be changed, along with nmbclusters. >=20 > This was why i sought opinions, of the algorithm itself, but also = anyone > using > ixgbe and igb in heavy use, what would you find most convenient? >=20 > Jack > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" --Apple-Mail=_D789DF06-0C84-453C-AD51-1C13DBE43289--
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