On 14-Nov-19 8:12 AM, Venumadhav Josyula wrote:
Hi Oliver,Bruce,
* we were using --SOCKET-MEM Eal flag.
* We did not wanted to avoid going back to legacy mode.
* we also wanted to avoid 1G huge-pages.
Thanks for your inputs.
Hi Anatoly,
We were using vfio with iommu, but by default it s iova-mode=pa, after
changing to iova-mode=va via EAL it kind of helped us to bring down
allocation time(s) for mempools drastically. The time taken was brought
from ~4.4 sec to 0.165254 sec.
Thanks and regards
Venu
That's great to hear.
As a final note, --socket-mem is no longer necessary, because 18.11 will
allocate memory as needed. It is however still advisable to use it if
you see yourself end up in a situation where the runtime allocation
could conceivably fail (such as if you have other applications running
on your system, and DPDK has to compete for hugepage memory).
I would also suggest using --limit-mem if you desire to limit the
maximum amount of memory DPDK will be able to allocate. This will make
DPDK behave similarly to older releases in that it will not attempt to
allocate more memory than you allow it.
On Wed, 13 Nov 2019 at 22:56, Burakov, Anatoly
<anatoly.bura...@intel.com <mailto:anatoly.bura...@intel.com>> wrote:
On 13-Nov-19 9:19 AM, Bruce Richardson wrote:
> On Wed, Nov 13, 2019 at 10:37:57AM +0530, Venumadhav Josyula wrote:
>> Hi ,
>> We are using 'rte_mempool_create' for allocation of flow memory.
This has
>> been there for a while. We just migrated to dpdk-18.11 from
dpdk-17.05. Now
>> here is problem statement
>>
>> Problem statement :
>> In new dpdk ( 18.11 ), the 'rte_mempool_create' take
approximately ~4.4 sec
>> for allocation compared to older dpdk (17.05). We have som 8-9
mempools for
>> our entire product. We do upfront allocation for all of them (
i.e. when
>> dpdk application is coming up). Our application is run to
completion model.
>>
>> Questions:-
>> i) is that acceptable / has anybody seen such a thing ?
>> ii) What has changed between two dpdk versions ( 18.11 v/s 17.05
) from
>> memory perspective ?
>>
>> Any pointer are welcome.
>>
> Hi,
>
> from 17.05 to 18.11 there was a change in default memory model
for DPDK. In
> 17.05 all DPDK memory was allocated statically upfront and that
used for
> the memory pools. With 18.11, no large blocks of memory are
allocated at
> init time, instead the memory is requested from the kernel as it
is needed
> by the app. This will make the initial startup of an app faster,
but the
> allocation of new objects like mempools slower, and it could be
this you
> are seeing.
>
> Some things to try:
> 1. Use "--socket-mem" EAL flag to do an upfront allocation of
memory for use
> by your memory pools and see if it improves things.
> 2. Try using "--legacy-mem" flag to revert to the old memory model.
>
> Regards,
> /Bruce
>
I would also add to this the fact that the mempool will, by default,
attempt to allocate IOVA-contiguous memory, with a fallback to non-IOVA
contiguous memory whenever getting IOVA-contiguous memory isn't
possible.
If you are running in IOVA as PA mode (such as would be the case if you
are using igb_uio kernel driver), then, since it is now impossible to
preallocate large PA-contiguous chunks in advance, what will likely
happen in this case is, mempool will try to allocate IOVA-contiguous
memory, fail and retry with non-IOVA contiguous memory (essentially
allocating memory twice). For large mempools (or large number of
mempools) that can take a bit of time.
The obvious workaround is using VFIO and IOVA as VA mode. This will
cause the allocator to be able to get IOVA-contiguous memory at the
outset, and allocation will complete faster.
The other two alternatives, already suggested in this thread by Bruce
and Olivier, are:
1) use bigger page sizes (such as 1G)
2) use legacy mode (and lose out on all of the benefits provided by the
new memory model)
The recommended solution is to use VFIO/IOMMU, and IOVA as VA mode.
--
Thanks,
Anatoly
--
Thanks,
Anatoly
