On Thu, Feb 23, 2012 at 9:19 AM, Fabien Thomas <fabien.tho...@netasq.com>wrote:
> > Le 22 févr. 2012 à 22:51, Jack Vogel a écrit : > > > On Wed, Feb 22, 2012 at 1:44 PM, Luigi Rizzo <ri...@iet.unipi.it> wrote: > > > >> 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. > >>> > >>> No, we kept hitting mbuf pool limits on 64-bit systems when we started > >>> working on FreeBSD support. > >> > >> ok never mind then, the mechanism would be the same, though > >> the limits (especially VM_LIMIT) would be different. > >> > >>>> Here is a possible approach: > >>>> > >>>> 1. nmbclusters consume the kernel virtual address space so there > >>>> must be some upper limit, say > >>>> > >>>> VM_LIMIT = 256000 (translates to 512MB of address space) > >>>> > >>>> 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... > >>>> > >>>> MEM_LIMIT = (physical_ram / 2) / 2048 > >>>> > >>>> 3. one may try to set a suitably large, desirable number of buffers > >>>> > >>>> TARGET_CLUSTERS = 128000 > >>>> > >>>> 4. and finally we could use the current default as the absolute > minimum > >>>> > >>>> MIN_CLUSTERS = 1024 + maxusers*64 > >>>> > >>>> Then at boot the system could say > >>>> > >>>> nmbclusters = min(TARGET_CLUSTERS, VM_LIMIT, MEM_LIMIT) > >>>> > >>>> nmbclusters = max(nmbclusters, MIN_CLUSTERS) > >>>> > >>>> > >>>> 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, > >>> > >>> 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. > >> > >>>> if necessary reducing the number of active queues. > >>> > >>> So now I have too few queues on my interface even after I increase the > >>> limit. > >>> > >>> There ought to be a standard way to configure numbers of queues and > >>> default queue lengths. > >> > >> 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. > >> > >> cheers > >> luigi > >> > > > > 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. > > > > 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. > If interfaces have the possibility to use more queues, they should, imo so I'm all for rasing the default size. For those systems with very limited memory it's easily changed. > > > After the installed kernel is booted and the admin would do whatever post > > install > > modifications they wish it could be changed, along with nmbclusters. > > > > 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? > > > > Jack > > _______________________________________________ > > freebsd-net@freebsd.org mailing list > > http://lists.freebsd.org/mailman/listinfo/freebsd-net > > To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org" > > _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
