[dpdk-dev] [PATCH 0/2] eal/malloc: fix wrong heap initialization over multiple memsegs
gowrishankar muthukrishnan
gowrishankar.m at linux.vnet.ibm.com
Sat May 19 03:35:34 CEST 2018
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 at linux.vnet.ibm.com>
>
>
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