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Date:      Sun, 08 Mar 2020 00:45:00 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 244665] Very slow NFS I/O during ZFS resilver - _sleep() sleeps really long...
Message-ID:  <bug-244665-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D244665

            Bug ID: 244665
           Summary: Very slow NFS I/O during ZFS resilver - _sleep()
                    sleeps really long...
           Product: Base System
           Version: 11.3-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: pen@lysator.liu.se

I've been investigating an issue we're having that gives our users a really
lousy NFS experience during ZFS resilver on one of our servers.=20

In order to try to pinpoint exactly what's going on I've tried various thin=
gs.
Lately I've been dtrace the call path for "mkdir()" and it seems that it is=
 the
_sleep() kernel call that sometimes sleeps for _really_ long times like 1-20
seconds...

Sure, the kernel is busy doing the ZFS resilver and other stuff but this is
silly... Any ideas? Too low priority of the _sleep (prio=3D99?) compared to=
 other
kernel threads so it never gets scheduled?


One example:

 21  54842               nfsrvd_dorpc:entry Start
 21  47273                 nfsv4_lock:entry Start(lp->nfslock_lock=3D6,
iwantlock=3D0)
 21  37590                  nfsmsleep:entry Start(ffffffff81e9982c,
ffffffff81e998a0, 99)
 21  54396                     _sleep:entry Start(prio=3D99, timeo=3D0)
 16  54397                    _sleep:return   10942618 =C2=B5s
 16  37591                 nfsmsleep:return   10942626 =C2=B5s
 16  37590                  nfsmsleep:entry Start(ffffffff81e9982c,
ffffffff81e998a0, 99)
 16  54396                     _sleep:entry Start(prio=3D99, timeo=3D0)
  7  54397                    _sleep:return        344 =C2=B5s
  7  37591                 nfsmsleep:return        352 =C2=B5s
  7  47274                nfsv4_lock:return   10942987 =C2=B5s
  7  13973           nfsrvd_statstart:entry Start
  7  13974          nfsrvd_statstart:return          2 =C2=B5s
  7  44369     nfsrv_mallocmget_limit:entry Start
  7  44370    nfsrv_mallocmget_limit:return          2 =C2=B5s
  7  13971             nfsrvd_statend:entry Start
  7  13972            nfsrvd_statend:return          2 =C2=B5s
  7  13973           nfsrvd_statstart:entry Start
  7  13974          nfsrvd_statstart:return          1 =C2=B5s
  7  51444                nfsrv_mtofh:entry Start
  7  51445               nfsrv_mtofh:return          2 =C2=B5s
  7  47329                nfsd_fhtovp:entry Start
  7  48059           __mtx_lock_flags:entry Start
  7  48060          __mtx_lock_flags:return          2 =C2=B5s
  7  47330               nfsd_fhtovp:return         14 =C2=B5s
  7  13971             nfsrvd_statend:entry Start
  7  13972            nfsrvd_statend:return          1 =C2=B5s
  7  13973           nfsrvd_statstart:entry Start
  7  13974          nfsrvd_statstart:return          1 =C2=B5s
  7  43887             nfsrvd_getattr:entry Start
  7  38608      nfsv4root_getreferral:entry Start
  7  38609     nfsv4root_getreferral:return          2 =C2=B5s
  7  43888            nfsrvd_getattr:return         22 =C2=B5s
  7  13971             nfsrvd_statend:entry Start
  7  13972            nfsrvd_statend:return          1 =C2=B5s
  7  54843              nfsrvd_dorpc:return   10943076 =C2=B5s

--=20
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