Re: [dpdk-dev] [PATCH] mempool: fix slow allocation of large mempools

[Ali Alnubani <alialnu@mellanox.com>]

Hi Olivier,

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Olivier Matz
> Sent: Thursday, January 9, 2020 3:28 PM
> To: dev@dpdk.org
> Cc: Andrew Rybchenko <arybchenko@solarflare.com>; Anatoly Burakov
> <anatoly.burakov@intel.com>; stable@dpdk.org
> Subject: [dpdk-dev] [PATCH] mempool: fix slow allocation of large mempools
> 
> When allocating a mempool which is larger than the largest available area, it
> can take a lot of time:
> 
> a- the mempool calculate the required memory size, and tries
>    to allocate it, it fails
> b- then it tries to allocate the largest available area (this
>    does not request new huge pages)
> c- add this zone to the mempool, this triggers the allocation
>    of a mem hdr, which request a new huge page
> d- back to a- until mempool is populated or until there is no
>    more memory
> 
> This can take a lot of time to finally fail (several minutes): in step
> a- it takes all available hugepages on the system, then release them after it
> fails.
> 
> The problem appeared with commit eba11e364614 ("mempool: reduce
> wasted space on populate"), because smaller chunks are now allowed.
> Previously, it had to be at least one page size, which is not the case in step b-.
> 
> To fix this, implement our own way to allocate the largest available area
> instead of using the feature from memzone: if an allocation fails, try to divide
> the size by 2 and retry. When the requested size falls below min_chunk_size,
> stop and return an error.
> 
> Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---

Testpmd (testpmd -n4 -- -i) fails to start after applying this patch with:
"""
EAL: Error - exiting with code: 1
  Cause: Creation of mbuf pool for socket 0 failed: File exists
"""

This is why the check ci/iol-mellanox-Performance is failing (not sure if the other tests are failing for the same reason).

Regards,
Ali