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This is a page tracks issues that we run into while testing the Multi-Rail Feature

Problem List

  • with 17 interfaces trying to discover on the any of the interface the first time returns an error "no route to host".
    • Ok was able to reproduce. If I follow the steps in UT-DD-EN-0005 exactly, then the first time I try to discover any of the nids it fails
    • steps to reproduce
      • P1 && P2
  756  lnetctl lnet configure
  757  lnetctl net add --net tcp --if eth0,eth1,eth2,eth3,eth4,eth5,eth6,eth7,eth8,eth9,eth10,eth11,eth12,eth13,eth14,eth15,eth16
 
P1:
lnetctl ping --nid 192.168.122.42@tcp


P2:
lnetctl ping --nid 192.168.122.23@tcp


P1:
[root@MRtest01 Lustre]# lnetctl discover --nid 192.168.122.46@tcp
manage:
    - discover:
          errno: -1
          descr: failed to discover 192.168.122.46@tcp: No route to host


Second time it works
  • With 17 interface discovered "show peer" hangs
    • When the rc from the kernel is not 0. The structure is not copied out of the kernel to user space. The code depends on that in order to pass the new size if the data to be copied out is too big for the buffer passed in by the user. Since that doesn't happen when rc == -E2BIG, user space code gets into an infinite loop sending IOCTLs to the kernel
    • from libcfs_ioctl()
 
145 »·······»·······»·······if (err == 0) {
146 »·······»·······»·······»·······if (copy_to_user(uparam, hdr, hdr->ioc_len))
147 »·······»·······»·······»·······»·······err = -EFAULT;
148 »·······»·······»·······}
149 »·······»·······»·······break;


The buffer is only copied to user space if the ioctl handler returns 0. Not really sure if it's safe to change that.
  • "lnetctl discover" command hangs with discovery off. This happened once, so an intermittent issue. Will try to reproduce.
  • "lnetctl discover" discovers the peer even with discovery off.
  • "lnetctl discover --force" expects a parameter (no parameter should be needed with --force).

  • Doug: I configured a Parallels VM with 16 interfaces (won't let me do 17 as 16 is a limit).  When I "lctl network configure" with no YAML or module parameters, I get this error from ksocklnd: "Mar 7 14:01:16 centos-7 kernel: LNet: 5111:0:(socklnd.c:2652:ksocknal_enumerate_interfaces()) Ignoring interface virbr0 (too many interfaces)".

  • Doug: When discovering a node with 16 interfaces via "lnetctl discover --nid", it works, but I am seeing this log: 

    Mar  7 15:48:04 centos-7 kernel: LNetError: 24769:0:(peer.c:1726:lnet_peer_push_event()) Push Put from unknown 0@<0:0> (source 0@<0:0>)

     

    • Olaf: I've seen the message before. Not sure how best to get rid of it, but it would be safe to just not emit it for the loopback case.
  • Doug: Tried the command "lnetctl set discovery" (no args) and got a core dump.
    • Olaf: As I recall, the problem is parse_long() is passed a NULL pointer for its number parameter in this case, and it doesn't check for that. Easiest to fix in parse_long() rather than fix all callers. This bug affects all lnetctl set commands.
  • Doug: How do I query the discovery setting?  There is no "lnetctl show discovery" (should there be?).  I tried "lnetctl set discovery" with no parameters and that core dumped (see previous bullet).  From a usability perspective, there is no obvious way to get this information.

  • Doug: When I enter "lnetctl set" to see what options I can set, I get this: 

    [root@centos-7 ~]# lnetctl set
set {tiny_buffers | small_buffers | large_buffers | routing}

    It does not mention "discovery" at all.

    • Olaf: So the text in list[] for the set subcommand needs to be updated. Note that max_interfaces needs to be added there as well.
  • When you do "lnetctl export" global section doesn't show discovery status

  • Doug: Test: UT-DD-EN-0002.  The first call to discover P2 fails with this: 

    [root@centos-7 ~]# lnetctl discover --nid 10.211.55.62@tcp
manage:
    - discover:
          errno: -1
          descr: failed to discover 10.211.55.62@tcp: No route to host

    The second attempt works as expected.  I repeated the test twice and got the same result each time.

  • Doug: Test: UT-DD-EN-0003.  Same behaviour as above.
  • Amir: There should be a way to turn off Multi-Rail. From the code the LNET_PING_FEAT_MULTI_RAIL is not unsettable.
  • Doug: Test: UT-DD-DIS-0001.  Test passed and worked as described.  However, I decided to run lnet-selftest to see how running some traffic after the test goes.  The lnet-selftest failed (never stopped running, did not show any stats).  I looked at top and can see that the "lnet-discovery" thread is using 70% CPU (it was not using any CPU prior to running lnet-selftest).  I suspect it is receiving all in coming traffic so lnet-selftest is not getting anything.  Additional note: I just redid the this test but ran lnet-selftest "before" trying to invoke discovery.  lnet-discovery thread still takes off and lnet-selftest locks.  Seems that turning off discovery causes lnet-discovery thread to misbehave.
  • Doug: After the previous point, I tried to kill the lnet-discovery thread.  It did not stop.  I then tried "kill -9".  It still did not stop.  I then did a reboot.  Node went away and could not complete the reboot because it could not unload LNet.  Had to reset the node.  We need a way to stop any of our worker threads when things do not go well.  Hard resetting a node in the field will be unacceptable to customers.

Usability Issues

  • Doug: How do I query the discovery setting?  There is no "lnetctl show discovery" (should there be?).  I tried "lnetctl set discovery" with no parameters and that core dumped (see previous section).  From a usability perspective, there is no obvious way to get this information.
  • Doug: I understand that Chris Morrone pushed for us to have "lnetctl set <key> <value>".  That breaks from the original paradigm to follow which was done with the Linux "ip" command.  It was designed to be: "ip <object> <action> <optional params>".  So, it would be more logical to have: "lnetctl discover set 0/1" than "lnetctl set discovery 0/1".  Then starting discovery can be: "lnetctl discover start <nids>".  Looking for discovery status can be: "lnetctl discovery show".  I found myself guessing at these commands as I have given here and had no idea to look at "set".
  • Doug: You set the max interfaces with "lnetctl set max_interfaces" but is it shown as "max_intf" in the global settings.  Should be the same for consistency.
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