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

[Hongtao Yu via Phabricator via llvm-commits]

hoy added a comment.

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.


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