[Tarantool-patches] [PATCH] test: stabilize flaky fiber memory leak detection

[Kirill Yukhin]

Hello,

On 29 янв 20:03, Alexander Turenko wrote:
> After #4736 regression fix (in fact it just reverts the new logic in
> small) it is possible again that a fiber's region may hold a memory for
> a while, but release it eventually. When the used memory exceeds 128 KiB
> threshold, fiber_gc() puts 'garbage' slabs back to slab_cache and
> subtracts them from region_used() metric. But until this point those
> slabs are accounted in region_used() and so in fiber.info() metrics.
> 
> This commit fixes flakiness of test cases of the following kind:
> 
>  | fiber.info()[fiber.self().id()].memory.used -- should be zero
>  | <...workload...>
>  | fiber.info()[fiber.self().id()].memory.used -- should be zero
> 
> The problem is that the first `<...>.memory.used` value may be non-zero.
> It depends of previous tests that were executed on this tarantool
> instance. It is resolved by restarting of a tarantool instance before
> such test cases to ensure that there are no 'garbage' slabs in a current
> fiber's region.
> 
> Note: This works only if a test case reserves only one slab at the
> moment: otherwise some memory may be hold after the case (and so a
> memory check after a workload will fail). However it seems that our
> cases are small enough to don't trigger this situation.
> 
> Call of region_free() would be enough, but we have no Lua API for it.
> 
> Fixes #4750.

I've checked your patch into 2.2, 2.3 and master as temporary
workaround.

--
Regards, Kirill Yukhin