[dpdk-users] Slow DPDK startup with many 1G hugepages
Marco Varlese
marco.varlese at suse.com
Thu Jun 1 12:12:08 CEST 2017
On Thu, 2017-06-01 at 08:50 +0000, Tan, Jianfeng wrote:
>
> >
> > -----Original Message-----
> > From: users [mailto:users-bounces at dpdk.org] On Behalf Of Imre Pinter
> > Sent: Thursday, June 1, 2017 3:55 PM
> > To: users at dpdk.org
> > Cc: Gabor Halász; Péter Suskovics
> > Subject: [dpdk-users] Slow DPDK startup with many 1G hugepages
> >
> > Hi,
> >
> > We experience slow startup time in DPDK-OVS, when backing memory with
> > 1G hugepages instead of 2M hugepages.
> > Currently we're mapping 2M hugepages as memory backend for DPDK OVS.
> > In the future we would like to allocate this memory from the 1G hugepage
> > pool. Currently in our deployments we have significant amount of 1G
> > hugepages allocated (min. 54G) for VMs and only 2G memory on 2M
> > hugepages.
> >
> > Typical setup for 2M hugepages:
> > GRUB:
> > hugepagesz=2M hugepages=1024 hugepagesz=1G hugepages=54
> > default_hugepagesz=1G
> >
> > $ grep hugetlbfs /proc/mounts
> > nodev /mnt/huge_ovs_2M hugetlbfs rw,relatime,pagesize=2M 0 0
> > nodev /mnt/huge_qemu_1G hugetlbfs rw,relatime,pagesize=1G 0 0
> >
> > Typical setup for 1GB hugepages:
> > GRUB:
> > hugepagesz=1G hugepages=56 default_hugepagesz=1G
> >
> > $ grep hugetlbfs /proc/mounts
> > nodev /mnt/huge_qemu_1G hugetlbfs rw,relatime,pagesize=1G 0 0
> >
> > DPDK OVS startup times based on the ovs-vswitchd.log logs:
> >
> > * 2M (2G memory allocated) - startup time ~3 sec:
> >
> > 2017-05-03T08:13:50.177Z|00009|dpdk|INFO|EAL ARGS: ovs-vswitchd -c 0x1
> > --huge-dir /mnt/huge_ovs_2M --socket-mem 1024,1024
> >
> > 2017-05-03T08:13:50.708Z|00010|ofproto_dpif|INFO|netdev at ovs-netdev:
> > Datapath supports recirculation
> >
> > * 1G (56G memory allocated) - startup time ~13 sec:
> > 2017-05-03T08:09:22.114Z|00009|dpdk|INFO|EAL ARGS: ovs-vswitchd -c 0x1
> > --huge-dir /mnt/huge_qemu_1G --socket-mem 1024,1024
> > 2017-05-03T08:09:32.706Z|00010|ofproto_dpif|INFO|netdev at ovs-netdev:
> > Datapath supports recirculation
> > I used DPDK 16.11 for OVS and testpmd and tested on Ubuntu 14.04 with
> > kernel 3.13.0-117-generic and 4.4.0-78-generic.
>
>
> You can shorten the time by this:
>
> (1) Mount 1 GB hugepages into two directories.
> nodev /mnt/huge_ovs_1G hugetlbfs rw,relatime,pagesize=1G,size=<how much you
> want to use in OVS> 0 0
> nodev /mnt/huge_qemu_1G hugetlbfs rw,relatime,pagesize=1G 0 0
I understood (reading Imre) that this does not really work because of non-
deterministic allocation of hugepages in a NUMA architecture.
e.g. we would end up (potentially) using hugepages allocated on different nodes
even when accessing the OVS directory.
Did I understand this correctly?
>
> (2) Force to use memory interleave policy
> $ numactl --interleave=all ovs-vswitchd ...
>
> Note: keep the huge-dir and socket-mem option, "--huge-dir /mnt/huge_ovs_1G --
> socket-mem 1024,1024".
>
> >
> >
> > We had a discussion with Mark Gray (from Intel), and he come up with the
> > following items:
> >
> > · The ~10 sec time difference is there with testpmd as well
> >
> > · They believe it is a kernel overhead (mmap is slow, perhaps it is
> > zeroing
> > pages). The following code from eal_memory.c does the above mentioned
> > printout in EAL startup:
>
> Yes, correct.
>
> >
> > 469 /* map the segment, and populate page tables,
> > 470 * the kernel fills this segment with zeros */
> > 468 uint64_t start = rte_rdtsc();
> > 471 virtaddr = mmap(vma_addr, hugepage_sz, PROT_READ | PROT_WRITE,
> > 472 MAP_SHARED | MAP_POPULATE, fd, 0);
> > 473 if (virtaddr == MAP_FAILED) {
> > 474 RTE_LOG(DEBUG, EAL, "%s(): mmap failed: %s\n", __func__,
> > 475 strerror(errno));
> > 476 close(fd);
> > 477 return i;
> > 478 }
> > 479
> > 480 if (orig) {
> > 481 hugepg_tbl[i].orig_va = virtaddr;
> > 482 printf("Original mapping of page %u took: %"PRIu64"
> > ticks, %"PRIu64" ms\n ",
> > 483 i, rte_rdtsc() - start,
> > 484 (rte_rdtsc() - start) * 1000 /
> > 485 rte_get_timer_hz());
> > 486 }
> >
> >
> > A solution could be to mount 1G hugepages to 2 separate directory: 2G for
> > OVS and the remaining for the VMs, but the NUMA location for these
> > hugepages is non-deterministic. Since mount cannot handle NUMA related
> > parameters during mounting hugetlbfs, and fstab forks the mounts during
> > boot.
>
> Oh, similar idea :-)
>
> >
> >
> > Do you have a solution on how to use 1G hugepages for VMs and have
> > reasonable DPDK EAL startup time?
>
> No, we still don't have such options.
>
> Thanks,
> Jianfeng
>
> >
> >
> > Thanks,
> > Imre
>
>
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