Re: [Qemu-ppc] Profiling results

[BALATON Zoltan]

On Tue, 17 Jul 2018, Mark Cave-Ayland wrote:
> > MorphOS on mac99 this seems to be significant. This is with default 
> > configure (--enable-qom-cast-debug):
> >
> > %?????? cum. %???? linenr info???????????????? symbol name
> > 9.7057?? 9.7057??? exec-all.h:410????????????? helper_lookup_tb_ptr
> > 8.0330? 17.7387??? object.c:711 
> > object_class_dynamic_cast_assert
> > 6.9411? 24.6798??? cputlb.c:793??????????????? io_readx
> > 6.3219? 31.0017??? sm501_template.h:62???????? draw_line16_32
> > 5.3601? 36.3617??? cputlb.c:114??????????????? tlb_flush_nocheck
> > 3.6170? 39.9787??? translate-all.c:749???????? page_trylock_add
> > 3.1188? 43.0975??? translate-all.c:803???????? page_collection_lock
> > 3.0405? 46.1380??? exec.c:3025???????????????? iotlb_to_section
> > 2.7044? 48.8424??? softmmu_template.h:112????? helper_ret_ldub_mmu
> > 2.4154? 51.2578??? memory.c:1350?????????????? memory_region_access_valid
[...]
> My first thought is that there is a QOM cast somewhere in a hot path on -M 
> mac99 - can you show us the call stack information from the profile?

Not really. Oprofile that gave me this profile could not display call 
graph for this call. I've tried again with the perf tool but I'm not quite 
sure how to interpret its results. If I'm not mistaken it points me in the 
direction of cpu_asidx_from_attrs, called from iotlb_to_section, called 
from io_readx. The object_class_dynamic_cast_assert call likely comes from 
OBJECT_CLASS_CHECK, expanded from OBJECT_GET_CLASS, expanded from 
CPU_GET_CLASS. Would that make any sense? Any idea what to do about it?

Thank you,
BALATON Zoltan