Re: tar x cpu bound

To: tech-kern%netbsd.org@localhost
Subject: Re: tar x cpu bound
From: Edgar Fuß <ef%math.uni-bonn.de@localhost>
Date: Mon, 12 May 2025 18:45:06 +0200

As suggested privately by riastradh@, I ran the tar command under dtrace
	dtrace -n 'profile:::profile-97 { @[stack()] = count() }' -c ...
and got output I can't make sense of. I attach the last (top-count) lines.

The first thing I don't understand is why the top (or the two top) hits 
are in idle_loop. Is that because the other fives cores are idle?

The second question is what the single number without a backtrace means.

And the third question is that I would have expected a large amount of 
hits in the write system call if the problem really was stdio to issue 
small writes.

              netbsd`0xffffffff8021ff62
              netbsd`intr_biglock_wrapper+0x16
              netbsd`Xhandle_ioapic_level5+0x6a
              netbsd`acpicpu_cstate_idle_enter+0xdb
              netbsd`acpicpu_cstate_idle+0xdb
              netbsd`idle_loop+0x111
              netbsd`lwp_trampoline+0x17
              287

              netbsd`0xffffffff8022008f
              netbsd`AcpiHwReadPort+0xc1
              netbsd`AcpiHwRead+0x11f
              netbsd`acpitimer_read_fast+0x11
              netbsd`acpicpu_cstate_idle_enter+0x82
              netbsd`acpicpu_cstate_idle+0xdb
              netbsd`idle_loop+0x111
              netbsd`lwp_trampoline+0x17
              292

              netbsd`0xffffffff8021ff62
              netbsd`intr_biglock_wrapper+0x16
              netbsd`Xhandle_ioapic_level5+0x6a
              netbsd`biodone2+0x6d
              netbsd`biointr+0x33
              netbsd`softint_dispatch+0x91
              netbsd`Xsoftintr+0x4f
              297

              netbsd`0xffffffff8022008f
              netbsd`AcpiHwReadPort+0xc1
              netbsd`AcpiHwRead+0x11f
              netbsd`acpitimer_read_fast+0x11
              netbsd`acpicpu_cstate_idle_enter+0x1c
              netbsd`acpicpu_cstate_idle+0xdb
              netbsd`idle_loop+0x111
              netbsd`lwp_trampoline+0x17
              314

              netbsd`ufs_lookup+0x2f7
              netbsd`VOP_LOOKUP+0x4d
              netbsd`lookup_once+0x18d
              netbsd`namei_tryemulroot.constprop.9+0x3c5
              netbsd`namei+0x43
              netbsd`fd_nameiat.isra.2+0x54
              netbsd`do_sys_renameat.isra.6+0x155
              netbsd`syscall+0x1ec
              netbsd`handle_syscall+0x2d
              431

              netbsd`ufs_lookup+0x2f7
              netbsd`VOP_LOOKUP+0x4d
              netbsd`relookup+0x42
              netbsd`do_sys_renameat.isra.6+0x2ef
              netbsd`syscall+0x1ec
              netbsd`handle_syscall+0x2d
              436

              netbsd`ufs_lookup+0x2f7
              netbsd`VOP_LOOKUP+0x4d
              netbsd`relookup+0x42
              netbsd`ufs_gro_lookup+0x3c
              netbsd`genfs_sane_rename+0x1e7
              netbsd`ufs_sane_rename+0x3a
              netbsd`genfs_insane_rename+0x93
              netbsd`VOP_RENAME+0x7c
              netbsd`do_sys_renameat.isra.6+0x4d1
              netbsd`syscall+0x1ec
              netbsd`handle_syscall+0x2d
              443

              netbsd`ufs_lookup+0x2f7
              netbsd`VOP_LOOKUP+0x4d
              netbsd`lookup_once+0x18d
              netbsd`namei_tryemulroot.constprop.9+0x3c5
              netbsd`namei+0x43
              netbsd`vn_open+0xa3
              netbsd`do_open+0x112
              netbsd`do_sys_openat+0x68
              netbsd`sys_open+0x24
              netbsd`syscall+0x1ec
              netbsd`handle_syscall+0x2d
              486

              netbsd`ufs_lookup+0x2f7
              netbsd`VOP_LOOKUP+0x4d
              netbsd`relookup+0x42
              netbsd`ufs_gro_lookup+0x3c
              netbsd`genfs_sane_rename+0x1a5
              netbsd`ufs_sane_rename+0x3a
              netbsd`genfs_insane_rename+0x93
              netbsd`VOP_RENAME+0x7c
              netbsd`do_sys_renameat.isra.6+0x4d1
              netbsd`syscall+0x1ec
              netbsd`handle_syscall+0x2d
              512

              netbsd`ufs_lookup+0x2f7
              netbsd`VOP_LOOKUP+0x4d
              netbsd`lookup_once+0x18d
              netbsd`namei_tryemulroot.constprop.9+0x3c5
              netbsd`namei+0x43
              netbsd`fd_nameiat.isra.2+0x54
              netbsd`do_sys_renameat.isra.6+0xc3
              netbsd`syscall+0x1ec
              netbsd`handle_syscall+0x2d
              556

              netbsd`0xffffffff8021ff62
              netbsd`biodone2+0x6d
              netbsd`biointr+0x33
              netbsd`softint_dispatch+0x91
              netbsd`Xsoftintr+0x4f
              560

              611

              netbsd`0xffffffff8021ff3e
              netbsd`acpicpu_cstate_idle_enter+0xdb
              netbsd`acpicpu_cstate_idle+0xdb
              netbsd`idle_loop+0x111
              netbsd`lwp_trampoline+0x17
            86750

              netbsd`Xspllower+0xe
              netbsd`md_root_setconf
              203

              netbsd`uvm_map_space_avail.constprop.0+0x5c
              netbsd`uvm_map+0xd8
              netbsd`uvm_pagermapin+0x97
              netbsd`genfs_gop_write+0x2d
              netbsd`genfs_do_putpages+0x661
              netbsd`VOP_PUTPAGES+0x43
              netbsd`ffs_full_fsync+0x146
              netbsd`VOP_FSYNC+0x47
              netbsd`sched_sync+0x15b
              netbsd`lwp_trampoline+0x17
              362

              netbsd`_kernel_lock+0xca
              netbsd`cv_wait+0xb7
              netbsd`DAGExecutionThread+0x136
              netbsd`lwp_trampoline+0x17
              507

              netbsd`_kernel_lock+0xca
              netbsd`spec_strategy+0x58
              netbsd`VOP_STRATEGY+0x3c
              netbsd`dkstart+0x13e
              netbsd`bdev_strategy+0x81
              netbsd`spec_strategy+0x58
              netbsd`VOP_STRATEGY+0x3c
              netbsd`genfs_do_io+0x16a
              netbsd`genfs_gop_write+0x52
              netbsd`genfs_do_putpages+0x661
              netbsd`VOP_PUTPAGES+0x43
              netbsd`ffs_full_fsync+0x146
              netbsd`VOP_FSYNC+0x47
              netbsd`sched_sync+0x15b
              netbsd`lwp_trampoline+0x17
              926

              netbsd`_kernel_lock+0xca
              netbsd`cv_wait+0xb7
              netbsd`rf_RaidIOThread+0x14e
              netbsd`lwp_trampoline+0x17
             1691

             2124

              netbsd`x86_stihlt+0x6
              netbsd`idle_loop+0xb7
              netbsd`lwp_trampoline+0x17
             3894

              netbsd`x86_stihlt+0x6
              netbsd`idle_loop+0xb7
              netbsd`md_root_setconf
            25933

Follow-Ups:
- Re: tar x cpu bound
  - From: Christoph Badura
- Re: tar x cpu bound
  - From: RVP
- Re: tar x cpu bound
  - From: RVP
- re: tar x cpu bound
  - From: matthew green

References:
- tar x cpu bound
  - From: Edgar Fuß
- Re: tar x cpu bound
  - From: Edgar Fuß

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