Re: new module 'aligned-malloc'

[Florian Weimer]

* Paul Eggert:

> On 7/23/20 5:24 AM, Florian Weimer wrote:
>> Ah, 4096 is too small.
>>
>> For large allocations (above the mmap threshold), what happens in the
>> example is that the process VMA limit is eventually exhausted, at which
>> malloc falls back to sbrk, and then the algorithm succeeds.  I don't
>> think it's a good idea to trigger ENOMEM, it's certainly not
>> thread-safe.
>
> I'm not sure I see what ENOMEM has to do with it if the algorithm is
> succeeding.

During the mmap phase, the algorithm never achieves alignment.  Once
mmap fails with ENOMEM (likely because the number of VMAs would exceed
the per-process limit), malloc switch to the brk heap, where the
algorithm eventually produces an aligned allocation.  Only then the loop
terminates.

Thanks,
Florian