Re: [dpdk-dev] [PATCH 0/2] eal/malloc: fix wrong heap initialization over multiple memsegs

[gowrishankar muthukrishnan <gowrishankar.m@linux.vnet.ibm.com>]

Hi Thomas,

On Friday 18 May 2018 06:40 PM, Thomas Monjalon wrote:
> Hi,
>
> What is the status of DPDK 18.05 on IBM POWER?
>
> This patch suggests there are some issues but there were no news for
> two weeks, after comments from Anatoly.
> Are we going to release a DPDK which does not work well on POWER?

This issue is not applicable in v18.05 onwards (due to memory rework 
changes there).

Apologies for no update meanwhile, I will check on Anatoly's comments 
and get back.
My idea is to address this before next candidate ready on LTS releases 
(v17.11, v16.11).

Regards,
Gowrishankar
>
> 03/05/2018 12:11, Gowrishankar:
>> When there are multiple memsegs (each per hugepage), there are couple of
>> problems observed:
>>
>>    1. Same heap size index is always chosen to add new malloc_elems
>>       again and again, while there is an increasing heap size actually.
>>       Hence, when there is memalloc request for size *more than*
>>       elem->size available in free heap, malloc_heap_alloc would fail.
>>       In elem_start_pt(), we are actually relying on elem->size at the
>>       best, for finding suitable element, which is lower than requested
>>       size, in this case.
>>
>>       Hence, patch 1 in this series addresses this by merging
>>       contiguous malloc_elem (by virt addresses), so that there is
>>       better chance of finding suitable elem for the requested size.
>>       
>>    2. Even after resizing the heap malloc_elems, its free_head index
>>       is still the same, as the memsegs are just added in every malloc_
>>       elem. If larger memory is requested in rte_malloc, in a way
>>       that, heap index of requested size is beyond the slot where the
>>       entire heap is available, malloc_heap_alloc would fail.
>>       Because, at the time of heap init, only the lower index is
>>       always chosen to fill up memsegs. Hence, patch 2 addresses this
>>       by moving the list of malloc_elems into new slot in heap, as its
>>       size grows.
>>       
>> We encountered these situations as we run ip_reassembly example app,
>> when multiple segments are created in VA (when overcommit hugepages set
>> in powerpc arch).
>>
>> These problems are found only in the current releases (until v18.05
>> which carries new implementation for dynamic memory allocation).
>> These patches are tested with unit tests as well as some of the
>> examples apps. I request more testing if possible, on other archs
>> as these are problems in available LTS codes as well.
>>
>> Signed-off-by: Gowrishankar Muthukrishnan <gowrishankar.m@linux.vnet.ibm.com>
>
>