Mimalloc vs dlmalloc

[technopedi]

A multithreaded application is causing memory access out of bounds with Mimalloc , but doesn't cause any issue with any other allocator like dlmalloc. I have enabled pthreads as well. What could be the possible reason of same?

[sbc100]

It could be a bug in mimalloc, or it could be existing memory corruption bug doesn't show up except under certain memory layout conditions.

Can you try emmalloc? Can you try mimalloc + -fsanitize=address?

[technopedi]

I get issue in mimalloc with below stack. Can we say that memory was exhausted

[kripken]

An access out of bounds sounds like a bug in mimalloc or our port of it. Can you provide a testcase?

The bug could be related to memory being exhausted, if there is a code path that doesn't handle OOM properly.

[technopedi]

How can new give memory access out of bounds? Shouldn't it be coming when trying to access something out of buffer allocated?

[kripken]

A bug inside new itself could cause strange things like this. Without a testcase it's hard to say. But in general, you are right that the more likely reason for an access out of bounds is a read past a buffer size.

[technopedi]

I'm trying to figure out the best test case and reduce the application into this error.Because unfortunately the asan+mimalloc in my application is giving heap_buffer_overflow in starting on main itself, due to which unable to use asan to figure out memory access out of bounds issue. Meanwhile is it safe to assume that if list of heaps per thread is exhausted, then block->next will ideally return garbage value, resulting in memory access out of bounds?

[gozetor]

After switching to mimalloc, we started seeing the exact same problem - we are pretty sure that the reason is the memory exhaustion. We don't have the same issue with dlmalloc, but there is a very high overhead in our multithreaded app.
We think that the reason is that mimalloc does not free memory pages as aggressively.
Maybe there are some mimalloc settings that may improve that. I tried a few, but they don't change much.