Messages in this thread | | | From | Diwakar Tundlam <> | Date | Fri, 4 May 2012 16:18:08 -0700 | Subject | RE: [PATCH] sched: Enable arch-specific asym packing option in sched domain |
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Thanks for clarifying the Power7. I see the point - package vs cpu's within a package.
Yes, this is for Nvidia's ARM Quad-core Tegra CPU. It is a single package, organized flatly. To save power, we want cores to be loaded up in order from cpu0, 1, etc. The ASYM_PACKING flag seems to do exactly what we need if set in the domain flag.
Thanks, --Diwakar.
-----Original Message----- From: Peter Zijlstra [mailto:a.p.zijlstra@chello.nl] Sent: Friday, May 04, 2012 3:30 PM To: Diwakar Tundlam Cc: 'Ingo Molnar'; 'Andrew Morton'; 'Christoph Lameter'; 'Michael Neuling'; 'Stephen Rothwell'; 'Benjamin Herrenschmidt'; 'David Rientjes'; 'linux-kernel@vger.kernel.org'; Peter De Schrijver Subject: RE: [PATCH] sched: Enable arch-specific asym packing option in sched domain
On Fri, 2012-05-04 at 15:18 -0700, Diwakar Tundlam wrote: > > arch_sd_sibling_asym_packing() is already present under ifdef CONFIG_SMT. > I didn't touch that. I only added it to SD_CPU_INIT for all cpu's. > I assumed Power7 shouldn't use SD_CPU_INIT.
All archs use SD_CPU_INIT, its the default topology level for a package/socket. So now you've made Power7 prefer lower numbered sockets over higher numbered sockets.. not fatal, but not really nice either.
[ power7 is the only one that implements arch_sd_sibling_asym_packing ]
> Maybe I should define a separate weak symbol, say arch_sd_bias_to_lower_num_cpu()? > Then Power7 can define arch_sd_sibling_asym_packing() to be '1' and it > will not break all-cpu init.
A slightly saner name would be:
arch_sd_package_asym_packing()
FWIW, I suspect you're wanting to use this for some ARM chip (nvidia doesn't do much else -- aside from this graphics stuff) so that if there's hardly anything it runs on cpu0. Now, last time I checked, these ARM things had only 1 package, so I still don't see the point :-)
I suspect you want to modify SD_MC_INIT() with something like:
arch_sd_mc_asym_packing()
Or is this the big-little thing and you're representing them as separate packages?
See how a little extra information avoids me having to endlessly second guess wtf you're actually wanting to do?
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