Re: [Qemu-devel] [PATCH v4 00/11] TCG optimizations for 2.10

[Aurelien Jarno]

On 2017-04-26 23:29, Emilio G. Cota wrote:
> v3 for context: 
> https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg04795.html
> 
> Changes from v3:
> 
> - Added reviewed-by tags.
> 
> - Added a couple of suggested-by tags that I forgot to add in v3
>   regarding lookup_and_goto_ptr and i386's implementation of goto_ptr.
> 
> - lookup_tb_ptr
>   + Dropped the unnecessary exit_request check, as suggested by Paolo and
>     Richard.
>   + Only get the CPU state if we get a tb from the jmp_cache, as suggested
>     by Richard.
>   + Added tb_htable_lookup if we miss in tb_jmp_cache, as suggested by
>     Richard. This requires an extra patch to export tb_htable_lookup.
> 
> - goto_ptr: add IMPL(has_goto_ptr), as pointed out by Richard.
> 
> - target/arm: added a comment about gen_jr. See the v3 thread for why
>   it is needed.
> 
> - target/i386: use TCGV_UNUSED instead of (ab)using NULL on a TCGv,
>   as suggested by Richard. Also took his suggestion to simplify
>   the addition of jr + cs_base.
>   To minimize churn I renamed gen_eob_worker to do_gen_eob_worker,
>   which takes the newly added argument.
> 
> I have *not* re-run all experiments, because it takes several hours and
> performance hasn't changed much from v3, as can be seen in these two charts:
> * spec06int user-mode, test input, v2.9.0 baseline: http://imgur.com/ME2eMq1
> * spec06int softmmu, test input, v3 baseline: http://imgur.com/Clolu9Z
> The perf differences are mostly due to adding the htable check. Note that
> its impact is small, since tb_jmp_cache has a %hit rate in the high 90's.
> 
> You can inspect/fetch the changes at:
>   https://github.com/cota/qemu/tree/tcg-opt-v4

Thanks for this patchset. I have tested it with an arm target, but also
with a mips target with and additional patch. I haven't done any precise
benchmark yet. The patch is trivial and only changes 3 lines, but I am
not 100% sure I have done things correctly (see my comment on patch 7).

Tested-by: Aurelien Jarno <address@hidden>

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
address@hidden                 http://www.aurel32.net