Re: [dpdk-stable] [dpdk-dev] [PATCH v2] mempool: fix slow allocation of large mempools

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 1/17/20 1:01 PM, Olivier Matz wrote:
> On Fri, Jan 17, 2020 at 10:51:49AM +0100, Olivier Matz wrote:
>> 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>
> 
> Sorry I forgot to report Anatoly's ack on v1
> http://patchwork.dpdk.org/patch/64370/
> 
> Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

Reviewed-by: Andrew Rybchenko <arybchenko@solarflare.com>