Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1190049

Having Linux handle different "types" of memory

Show all headers | View raw

Hello everyone,

I'm using an ARMv7 platform (Cortex A9) on Linux 3.14

The system supports two memory modules.

For performance reasons, memory is "transparently" interleaved
(with a 128-byte grain). That is, when the CPU accesses addresses
0-127, it hits DRAM0; addresses 128-255, it hits DRAM1, and so on.

The problem is that other devices in the system, mainly the
Ethernet controller, didn't get the "transparent interleaving"
treatment. They just see DRAM0 and DRAM1. And I'm guessing this
will generate all kinds of "interesting" problems when I try to
DMA from the Ethernet controller's memory to DRAM...

Is there a way to tell Linux:

1) this 1GB memory chunk here is for you and your private allocations,
but don't use it for talking to devices/peripherals.

2) this 1GB memory chunk there is for talking to devices/peripherals,
but it has lower performance, so try not to use it for your own
private memory pools, but you can if memory is /really/ tight.

Is there something like this?

Maybe one of the NUMA policies?
https://www.kernel.org/doc/Documentation/vm/numa_memory_policy.txt
(I don't see any arch/arm/mm/numa.c however)

Maybe I can pretend that there is some kind of IOMMU?
https://www.kernel.org/doc/Documentation/DMA-API-HOWTO.txt
arch/arm/include/asm/dma-iommu.h

Or maybe there is an obvious solution that I'm missing?

Regards.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Having Linux handle different "types" of memory Mason <slash.tmp@free.fr> - 2015-07-22 17:20 +0200
  Re: Having Linux handle different "types" of memory Laura Abbott <labbott@redhat.com> - 2015-07-22 18:30 +0200

csiph-web