Date: Sun, 3 Mar 2024 16:28:23 -0800 From: Rick Macklem <rick.macklem@gmail.com> To: Garrett Wollman <wollman@bimajority.org> Cc: stable@freebsd.org Subject: Re: 13-stable NFS server hang Message-ID: <CAM5tNy7Ezs2XnAiWAf2wBrROhweyfWoeq2k%2B0Qqk4KCtw25ReA@mail.gmail.com> In-Reply-To: <CAM5tNy47qzCSCxUik3LyV=VtpYGgaLoWehP4AeJCXz0ik0JGaw@mail.gmail.com> References: <26078.50375.679881.64018@hergotha.csail.mit.edu> <CAM5tNy7ZZ2bVLmYnOCWzrS9wq6yudoV5JKG5ObRU0=wLt1ofZw@mail.gmail.com> <26083.64612.717082.366639@hergotha.csail.mit.edu> <CAM5tNy4BM3fwccjF53ROP-7NojsWMM2fUY2_RA-4GMWfc6Sn4g@mail.gmail.com> <CAM5tNy47qzCSCxUik3LyV=VtpYGgaLoWehP4AeJCXz0ik0JGaw@mail.gmail.com>
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On Sun, Mar 3, 2024 at 3:27=E2=80=AFPM Rick Macklem <rick.macklem@gmail.com= > wrote: > > On Sun, Mar 3, 2024 at 1:17=E2=80=AFPM Rick Macklem <rick.macklem@gmail.c= om> wrote: > > > > On Sat, Mar 2, 2024 at 8:28=E2=80=AFPM Garrett Wollman <wollman@bimajor= ity.org> wrote: > > > > > > > > > I wrote previously: > > > > PID TID COMM TDNAME KSTACK > > > > 997 108481 nfsd nfsd: master mi_switch sleepq= _timedwait _sleep nfsv4_lock nfsrvd_dorpc nfssvc_program svc_run_internal s= vc_run nfsrvd_nfsd nfssvc_nfsd sys_nfssvc amd64_syscall fast_syscall_common > > > > 997 960918 nfsd nfsd: service mi_switch sleepq= _timedwait _sleep nfsv4_lock nfsrv_setclient nfsrvd_exchangeid nfsrvd_dorpc= nfssvc_program svc_run_internal svc_thread_start fork_exit fork_trampoline > > > > 997 962232 nfsd nfsd: service mi_switch _cv_wa= it txg_wait_synced_impl txg_wait_synced dmu_offset_next zfs_holey zfs_freeb= sd_ioctl vn_generic_copy_file_range vop_stdcopy_file_range VOP_COPY_FILE_RA= NGE vn_copy_file_range nfsrvd_copy_file_range nfsrvd_dorpc nfssvc_program s= vc_run_internal svc_thread_start fork_exit fork_trampoline > > > > > > I spent some time this evening looking at this last stack trace, and > > > stumbled across the following comment in > > > sys/contrib/openzfs/module/zfs/dmu.c: > > > > > > | /* > > > | * Enable/disable forcing txg sync when dirty checking for holes wi= th lseek(). > > > | * By default this is enabled to ensure accurate hole reporting, it= can result > > > | * in a significant performance penalty for lseek(SEEK_HOLE) heavy = workloads. > > > | * Disabling this option will result in holes never being reported = in dirty > > > | * files which is always safe. > > > | */ > > > | int zfs_dmu_offset_next_sync =3D 1; > > > > > > I believe this explains why vn_copy_file_range sometimes takes much > > > longer than a second: our servers often have lots of data waiting to > > > be written to disk, and if the file being copied was recently modifie= d > > > (and so is dirty), this might take several seconds. I've set > > > vfs.zfs.dmu_offset_next_sync=3D0 on the server that was hurting the m= ost > > > and am watching to see if we have more freezes. > > > > > > If this does the trick, then I can delay deploying a new kernel until > > > April, after my upcoming vacation. > > Interesting. Please let us know how it goes. > Btw, I just tried this for my trivial test and it worked very well. > A 1Gbyte file was cpied in two Copy RPCs of 1sec and slightly less than > 1sec. Oops, I spoke too soon. The Copy RPCs worked fine (as above) but the Commit RPCs took a long time, so it still looks like you may need the patches. rick > > So, your vacation may be looking better, rick > > > > > And enjoy your vacation, rick > > > > > > > > -GAWollman > > >
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