On Sat, Mar 2, 2024 at 8:28 PM Garrett Wollman <woll...@bimajority.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 svc_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_wait > > txg_wait_synced_impl txg_wait_synced dmu_offset_next zfs_holey > > zfs_freebsd_ioctl vn_generic_copy_file_range vop_stdcopy_file_range > > VOP_COPY_FILE_RANGE vn_copy_file_range nfsrvd_copy_file_range nfsrvd_dorpc > > nfssvc_program svc_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 with > 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 = 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 modified > (and so is dirty), this might take several seconds. I've set > vfs.zfs.dmu_offset_next_sync=0 on the server that was hurting the most > 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.
And enjoy your vacation, rick > > -GAWollman >
