[PATCH] D107097: [llvm-profgen] An option to ignore parsing MMap events

[Lei Wang via Phabricator via llvm-commits]

wlei added a comment.

In D107097#2914659 <https://reviews.llvm.org/D107097#2914659>, @hoy wrote:

> In D107097#2914645 <https://reviews.llvm.org/D107097#2914645>, @wlei wrote:
>
>> In D107097#2914634 <https://reviews.llvm.org/D107097#2914634>, @hoy wrote:
>>
>>> In D107097#2914616 <https://reviews.llvm.org/D107097#2914616>, @wlei wrote:
>>>
>>>> In D107097#2914552 <https://reviews.llvm.org/D107097#2914552>, @hoy wrote:
>>>>
>>>>> In D107097#2914528 <https://reviews.llvm.org/D107097#2914528>, @wlei wrote:
>>>>>
>>>>>> In D107097#2914487 <https://reviews.llvm.org/D107097#2914487>, @hoy wrote:
>>>>>>
>>>>>>> Can the mmap events be treated as optional, so when they present we parse them otherwise just move forward to other events?
>>>>>>
>>>>>> That might have issues with the leading samples before we meet a MMAP, they won't know which binary it belongs to. Currently If not specify `ignore-mmap-events`, we will always check the `Addr2Binary` table which is empty without mmap events parsed.
>>>>>
>>>>> Can this be fixed? Without mmap events we can just use the preferred address as the load address.
>>>>>
>>>>> It sounds a bit unclear to me by giving `ignore-mmap-events` when the map events are there. That means we basically do not trust those events.
>>>>
>>>> Understood! My concern is if the scripts has mmap events and only the leading sample missed the load address, they still can be loaded at a different base address which is not the preferred address. it's wrong base address in that case,
>>>
>>> If that's a real case, we'll need to fix that. For now I think we want to cover to cases: 1. with leading mmaps 2. without leading mmaps (assuming the preferred address is the real load address). Have you seen a third case? I'm wondering if the input is invalid.
>>
>> Oh, I see, you mean if turn on `--show-mmap-events`, it will always have the leading mmap event, otherwise it's the invalid input? I indeed haven't seen the third case before. If so, that makes sense to use preferred address when without leading mmaps.
>
> I think `--show-mmap-events` should always give leading mmap events or no mmap events at all. We should warn or error out when only interior mmap events are seen.

That makes sense, let me change it, thanks for the feedback!


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107097/new/

https://reviews.llvm.org/D107097