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Re: [Qemu-devel] [PATCH v2 0/3] memory: an optimization
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH v2 0/3] memory: an optimization |
Date: |
Tue, 23 Feb 2016 11:49:35 +0800 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, 02/22 11:22, Paolo Bonzini wrote:
>
>
> On 22/02/2016 09:34, Gonglei wrote:
> > Perf top tells me qemu_get_ram_ptr consume some cpu cycles.
> >
> > Before this optimization:
> > 1.26% qemu-kvm [.] qemu_get_ram_ptr
> > 0.89% qemu-kvm [.] qemu_get_ram_block
> >
> > Applied the patch set:
> > 0.87% qemu-kvm [.] qemu_get_ram_ptr
> >
> > And Paolo suggested that we can get rid of qemu_get_ram_ptr
> > by storing the RAMBlock pointer into the memory region,
> > instead of the ram_addr_t value. And after appling this change,
> > I got much better performance indeed.
> >
> > BTW, PATCH 3 is an occasional find.
> >
> > v2:
> > - using 'struct RAMBlock *' instead of 'void *' in patch 1 [Fam]
> > - drop superfluous comments in patch 1 [Fam]
> >
> > Gonglei (3):
> > exec: store RAMBlock pointer into memory region
> > memory: optimize qemu_get_ram_ptr and qemu_ram_ptr_length
> > memory: Remove the superfluous code
> >
> > exec.c | 48 ++++++++++++++++++++++++++++++------------------
> > include/exec/memory.h | 8 ++++----
> > memory.c | 3 ++-
> > 3 files changed, 36 insertions(+), 23 deletions(-)
> >
>
> Thanks Lei and Fam, patches queued.
Thanks!
Actually I'd like to clean this up a bit more: moving assigning to
mr->ram_block from exec.c to memory.c, and drop mr->ram_addr.
I've already done these on top of master last Friday before v1 of this was
posted (oops! :), but I can rebase on top of these patches.
And upon that, I think we can replicate the ram_list.mru_block trick as
AddressSpaceDispatch.mru_section, to further reduce the calls to
qemu_get_ram_ptr.
Paolo, is there a git branch I can base off?
Fam