linux-kernel - RE: Memory policy question for NUMA arch....

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Message-ID: <301842.27948.qm@web111913.mail.gq1.yahoo.com>
Date:	Tue, 20 Apr 2010 13:34:10 -0700 (PDT)
From:	Chetan Loke <generationgnu@...oo.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	rick.sherm@...oo.com, andi@...stfloor.org,
	linux-numa@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: RE: Memory policy question for NUMA arch....

Lee,

--- On Mon, 4/19/10, Lee Schermerhorn <Lee.Schermerhorn@...com> wrote:
> You should never change the system default once the system
> is up and
> running.
> 

Not sure what I was thinking.Agreed, we should leave the default-policy alone.

> Still not clear on what your requirements are 

Thanks for pointing me to the other post. I might have a similar problem.I've a nehalem box.

1) Drivers supports MSI-X.
  1.1) Drivers at load time allocate a chunk of DMA'able memory.
   
2) Sometime later, after the OS boots, I need to load my apps.

3) Now, the apps and the drivers communicate via a mmap'd region.

I need a deterministic way of allocating memory depending on my needs(interleave or localalloc).So I can't be at the mercy of either 'current' or 'global-policy' or anyone else.Also, why reference 'current' to begin with? And everytime I reference 'current' from within my driver, current points to 'work_for_cpu' kthread. So that clearly doesn't help.

> A device-centric interface--e.g.,
> 'get_free_pages_dev()'--could get the
> device/bus node affinity via dev_to_node() and then do the
> allocation/conversion.   I think this is
> close to what you're suggesting
> above. See dma_generic_alloc_coherent() [in
> arch/x86/kernel/pci-dma.c]
> for an example of a wrapper that does the device affinity
> lookup and
> allocation in one function.
> 

> Of course, you could just do this in your driver, as well.
> 
Very helpful thanks.I will mimic 'dma_generic_alloc_coherent' in my driver when I need local-node memory.


> > Also, is there a way to configure irqbalance and ask
> it to leave these
> > guys alone? Like a config file that says - leave
> these
> > irqs/pci-devices alone.For now I've shut down
> irqbalance.
> 
> You can set the environment variable
> IRQBALANCE_BANNED_INTERRUPTS--when
> starting irqbalance--to list of interrupts that irqbalance
> should ignore
> if you're using a version that supports that.  Check
> the init script
> that starts irqbalance on your distro of choice.
> 
aaaah...mine is old and I could see IRQBALANCE_BANNED_CPUS and not _INTERRUPTS.I will upgrade it.

> Regards,
> Lee

Thanks
Chetan Loke



      

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