On 16-Sep-20 12:19 PM, Burakov, Anatoly wrote:
On 16-Sep-20 5:32 AM, Kamaraj P wrote:
Hi Anatoly,
We just dump the memory contents when it fails to allocate the memory.
Hi Kamaraj,
Yes, i can see that the memory is fragmented. That's not what i was
asking though, because memory fragmentation is *expected* if you're
using igb_uio. You're not using VFIO and IOVA as VA addressing, so
you're at the mercy of your kernel when it comes to getting
IOVA-contiguous address. We in DPDK cannot do anything about it, because
we don't control which pages we get and what addresses they get
assigned. There's nothing to fix on our side in this situation.
Here are the things you can do to avoid allocation failure in your case:
1) Drop the IOVA-contiguous allocation flag [1]
2) Use legacy mode [2] [3]
3) Switch to using VFIO [4]
4) Use bigger page size
The first point is crucial! Your allocation *wouldn't have failed* if
your code didn't specify for the allocation to require
IOVA-contiguousness. The fact that it has failed means that your
allocation has requested such memory, so it's on you to ensure that
whatever you're allocating, IOVA-contiguousness is *required*. I cannot
decide that for you as it is your code, so it is up to you to figure out
if whatever you're allocating actually requires such memory, or if you
can safely remove this allocation flag from your code.
[1]
http://doc.dpdk.org/api/rte__memzone_8h.html#a3ccbea77ccab608c6e683817a3eb170f
[2]
http://doc.dpdk.org/guides/prog_guide/env_abstraction_layer.html#memory-mapping-discovery-and-memory-reservation
[3] http://doc.dpdk.org/guides/linux_gsg/linux_eal_parameters.html#id3
[4] I understand the requirement for PF driver, but i think support for
PF in VFIO is coming in 20.11 release
Also, to add to this, we still haven't established that the allocation
error is in fact due to memory fragmentation. You *claim* that is the
case, but memory allocations can fail for other reasons, and you haven't
provided me with anything that would confirm this, as *merely* the fact
that the memory is fragmented will not, in and of itself, necessarily
cause any allocation failures *unless* you are trying to allocate memory
area that is bigger than your page size *and* is required to be contiguous.
If you can't tell me *what* you're allocating, at least tell me the size
of the allocation, the memzone flags it is allocated with, and any debug
log messages around the allocation, so that we can at least be sure that
we know the reason why the allocation fails. You're forcing me to fly
blind here, i can't help you if i don't know what i'm dealing with.
--
Thanks,
Anatoly
