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Re: [Qemu-devel] [PATCH] exec: limit system memory size
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] exec: limit system memory size |
Date: |
Mon, 4 Nov 2013 14:04:31 +0200 |
On Mon, Nov 04, 2013 at 12:22:35PM +0100, Paolo Bonzini wrote:
> Il 04/11/2013 12:14, Michael S. Tsirkin ha scritto:
> >> >
> >> > This patch looks good; however, on top of it can you test
> >> > kvm-unit-tests with TARGET_PHYS_ADDR_SPACE_BITS=64 and see whether
> >> > there is a measurable slowdown (in the inl_from_qemu tests)? If not,
> >> > we can just get rid of TARGET_PHYS_ADDR_SPACE_BITS in exec.c.
> > I'd rather we fixed a bug first - we need to fix it on stable too - any
> > cleanups can come on top.
>
> This is not necessarily a cleanup. Getting rid of
> TARGET_PHYS_ADDR_SPACE_BITS in exec.c means fixing device-to-device DMA
> bugs for example.
>
> Of course a smaller patch can be done that avoids the renaming of L2_*
> constants.
>
> > Also, I'm not sure what will this test tell
> > us: inl reads io space, not memory, right?
>
> The number of levels in the dispatch radix tree is independent of the
> size of the AddressSpace; it is P_L2_LEVELS for both the 64K io space
> and the 2^TARGET_PHYS_ADDRESS_SPACE_BITS memory space.
>
> Paolo
Hmm I think it's *at most* that deep but can be more shallow, no?
--
MST
Re: [Qemu-devel] [PATCH] exec: limit system memory size, Paolo Bonzini, 2013/11/04