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Re: [Qemu-devel] [PATCH 0/4] target/arm: Reduce overhead of cpu_get_tb_c
From: |
Laurent Desnogues |
Subject: |
Re: [Qemu-devel] [PATCH 0/4] target/arm: Reduce overhead of cpu_get_tb_cpu_state |
Date: |
Thu, 14 Feb 2019 11:28:48 +0100 |
Hi Richard,
On Thu, Feb 14, 2019 at 5:07 AM Richard Henderson
<address@hidden> wrote:
>
> We've talked about this before, caching state to reduce the
> amount of computation that happens looking up each TB.
>
> I know that Peter has been concerned that we would not be able to
> reliably maintain all of the places that need to be updates to
> keep this up-to-date.
>
> Well, modulo dirty tricks within linux-user, it appears as if
> exception delivery and return, plus after every TB-ending write
> to a system register is sufficient.
>
> There seems to be a noticable improvement, although wall-time
> is harder to come by -- all of my system-level measurements
> include user input, and my user-level measurements seem to be
> too small to matter.
FWIW this patch series made a run of linux-user AArch64 176.gcc 166.i
go from 29.5s down to 24.5s (on an E5-2650 v2). Though that'd need
more benchmarks, that looks quite good to me.
Thanks,
Laurent
>
> r~
>
>
> Richard Henderson (4):
> target/arm: Split out recompute_hflags et al
> target/arm: Rebuild hflags at el changes and MSR writes
> target/arm: Assert hflags is correct in cpu_get_tb_cpu_state
> target/arm: Rely on hflags correct in cpu_get_tb_cpu_state
>
> target/arm/cpu.h | 22 ++-
> target/arm/helper.h | 3 +
> target/arm/internals.h | 4 +
> linux-user/syscall.c | 1 +
> target/arm/cpu.c | 1 +
> target/arm/helper-a64.c | 3 +
> target/arm/helper.c | 267 ++++++++++++++++++++++---------------
> target/arm/machine.c | 1 +
> target/arm/op_helper.c | 1 +
> target/arm/translate-a64.c | 6 +-
> target/arm/translate.c | 14 +-
> 11 files changed, 204 insertions(+), 119 deletions(-)
>
> --
> 2.17.1
>
>
- [Qemu-devel] [PATCH 2/4] target/arm: Rebuild hflags at el changes and MSR writes, (continued)
- [Qemu-devel] [PATCH 2/4] target/arm: Rebuild hflags at el changes and MSR writes, Richard Henderson, 2019/02/13
- [Qemu-devel] [PATCH 1/4] target/arm: Split out recompute_hflags et al, Richard Henderson, 2019/02/13
- [Qemu-devel] [PATCH 4/4] target/arm: Rely on hflags correct in cpu_get_tb_cpu_state, Richard Henderson, 2019/02/13
- Re: [Qemu-devel] [PATCH 0/4] target/arm: Reduce overhead of cpu_get_tb_cpu_state,
Laurent Desnogues <=
- Re: [Qemu-devel] [PATCH 0/4] target/arm: Reduce overhead of cpu_get_tb_cpu_state, Alex Bennée, 2019/02/14
- Re: [Qemu-devel] [PATCH 0/4] target/arm: Reduce overhead of cpu_get_tb_cpu_state, Emilio G. Cota, 2019/02/14