dtrace_meta_lock[8] can become contentious under numerous conditions.
(Doc ID 2440527.1)
Last updated on JULY 07, 2023
Applies to:
Solaris Operating System - Version 10 1/13 U11 to 11.3 [Release 10.0 to 11.0]Information in this document applies to any platform.
Symptoms
Systems may experience unexpected performance impact, that is spiky. Looking at the lockstats output, you will see the lock dtrace_meta_lock[8] being very contentious. Note, the system does not have to be running dtrace directly to encounter this issue. A sample output of lockstat would look something like this (note the actual stack into the dtrace routine may be different from system to system.
Count indv cuml rcnt nsec Lock Hottest Caller
26 25% 84% 0.00 122228431 dtrace_meta_lock[8] dtrace_helper_provider_register+0x10
nsec ------ Time Distribution ------ count Stack
16384 |@ 1 dtrace_helper_slurp+0x21c
32768 |@ 1 dtrace_ioctl_helper+0xb0
65536 |@ 1 vnext_ioctl+0x70
131072 |@@ 2 sdev_fem_ioctl+0x78
262144 | 0 vhead_ioctl+0xe0
524288 | 0 fop_ioctl+0xd0
1048576 | 0 ioctl+0x16c
2097152 | 0 syscall_trap+0x228
Note the spin time on the lock, we are spinning an average of 0.12 seconds per event.
Also mutex blocks may show the issue
Adaptive mutex block: 240 events in 2.095 seconds (115 events/sec)
-------------------------------------------------------------------------------
Count indv cuml rcnt nsec Lock Hottest Caller
44 100% 100% 0.00 3814415376 dtrace_meta_lock[8] dtrace_helper_provider_register+0x10
nsec ------ Time Distribution ------ count Stack
33554432 | 1 dtrace_helper_slurp+0x21c
67108864 | 0 dtrace_ioctl_helper+0xb0
134217728 |@ 2 vnext_ioctl+0x70
268435456 | 1 sdev_fem_ioctl+0x78
536870912 |@@@ 5 vhead_ioctl+0xe0
1073741824 |@@ 3 fop_ioctl+0xd0
2147483648 |@@@@ 6 ioctl+0x16c
4294967296 |@@@@@@@ 14 syscall_trap+0x228
8589934592 |@@@ 5
17179869184 |@@@@ 6
34359738368 | 1
Which shows the mutex blocking for an average of almost 4 seconds per event.
Changes
Cause
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In this Document
| Symptoms |
| Changes |
| Cause |
| Solution |