Hi Andriy, thanks for your reply. I guess that contiguous memory is requested because of the performance reasons. Do you know if I can expect a noticeable performance drop using non-contiguous memory?
Renata On 10/04/2016 12:13 PM, Andriy Berestovskyy wrote: > Hi Renata, > DPDK supports non-contiguous memory pools, but > rte_pktmbuf_pool_create() uses rte_mempool_create_empty() with flags > set to zero, i.e. requests contiguous memory. > > As a workaround, in rte_pktmbuf_pool_create() try to pass > MEMPOOL_F_NO_PHYS_CONTIG flag as the last argument to > rte_mempool_create_empty(). > > Note that KNI and some PMDs in 16.07 still require contiguous memory > pools, so the trick might not work for your setup. For the KNI try the > DPDK's master branch which includes the commit by Ferruh Yigit: > > 8451269 kni: remove continuous memory restriction > > Regards, > Andriy > > > On Tue, Oct 4, 2016 at 11:38 AM, Renata Saiakhova > <Renata.Saiakhova at oneaccess-net.com> wrote: >> Hi Sergio, >> >> thank you for your quick answer. I also tried to allocate 1GB hugepage, but >> seems kernel fails to allocate it: previously I've seen that HugePages_Total >> in /proc/meminfo is set to 0, now - kernel hangs at boot time (don't know >> why). >> But anyway, if there is no way to control hugepage allocation in the sense >> they are in contiguous memory there is only way to accept it and adapt the >> code that it creates several pools which in total satisfy the requested >> size. >> >> Renata >> >> >> On 10/04/2016 10:27 AM, Sergio Gonzalez Monroy wrote: >>> On 04/10/2016 09:00, Renata Saiakhova wrote: >>>> Hi all, >>>> >>>> I'm using dpdk 16.04 (I tried 16.07 with the same results) and linux >>>> kernel 4.4.20 in a virtual machine (I'm using libvirt framework). I pass a >>>> parameter in kernel command line to allocate 512 hugepages of 2 MB at boot >>>> time. They are successfully allocated. When an application with dpdk starts >>>> it calls rte_pktmbuf_pool_create() which in turns requests internally >>>> 649363712 bytes. Those bytes should be allocated from one of rte_memseg. >>>> rte_memsegs describes contiguous portions of memory (both physical and >>>> virtual) built on hugepages. This allocation fails, because there are no >>>> rte_memsegs of this size (or bigger). Further debugging shows that >>>> hugepages >>>> are allocated in non-contiguous physical memory and therefore rte_memsegs >>>> are built respecting gaps in physical memory. >>>> Below are the sizes of segments built on hugepages (in bytes) >>>> 2097152 >>>> 6291456 >>>> 2097152 >>>> 524288000 >>>> 2097152 >>>> 532676608 >>>> 2097152 >>>> 2097152 >>>> So there are 5 segments which includes only one hugepage! >>>> This behavior is completely different to what I observe with linux kernel >>>> 3.8 (used with the same application with dpdk) - where all hugepages are >>>> allocated in contiguous memory. >>>> Does anyone experience the same issue? Could it be some kernel option >>>> which can do the magic? If not, and kernel can allocated hugepages in >>>> non-contiguous memory how dpdk is going to resolve it? >>>> >>> I don't think there is anything we can do to force the kernel to >>> pre-allocate contig hugepages on boot. If there was, we wouldn't need to do >>> all this mapping sorting and grouping we do on DPDK >>> as we would rely on the kernel giving us pre-allocated contig hugepages. >>> >>> If you have plenty of memory one possible work around would be to increase >>> the number of default hugepages so we are likely to find more contiguous >>> ones. >>> >>> Is using 1GB hugepages a possibility in your case? >>> >>> Sergio >>> >>>> Thanks in advance, >>>> Renata >>>> >>> . >>> > >
