Re: kern/55402: amd64/9.99.68/9.99.68: xen/zfs - kernel: double fault trap, code=0

[Frank Kardel <kardel%netbsd.org@localhost>]

Looking at the stack allocation I see quite a signiicant stack usage 
(10552 bytes)

each recursive invocation of dsl_scan_visitbp add 352+ bytes to the 
stack. Also

vdev_queue_io_to_issue framesize uses over 1 k of stack.

What is our kernel stack size?

0: vdev_queue_offset_compare framesize 8
1: vdev_queue_io_to_issue framesize 1152
2: vdev_queue_io_remove framesize 32
3: vdev_queue_io_to_issue framesize 1152
4: vdev_queue_io framesize 64
5: vdev_queue_io_done framesize 64
6: zio_vdev_io_start framesize 96
7: zio_execute framesize 80
8: zio_nowait framesize 48
9: vdev_mirror_io_start framesize 128
10: zio_vdev_io_start framesize 96
11: zio_execute framesize 80
12: zio_nowait framesize 48
13: vdev_mirror_io_start framesize 128
14: zio_vdev_io_start framesize 96
15: zio_execute framesize 80
16: zio_nowait framesize 48
17: zio_ddt_read_start framesize 256
18: zio_execute framesize 80
19: zio_nowait framesize 48
20: dsl_scan_scrub_cb framesize 160
21: dsl_scan_visitbp framesize 352
22: dsl_scan_visitbp framesize 352
23: dsl_scan_visitbp framesize 352
24: dsl_scan_visitdnode framesize 144
25: dsl_scan_visitbp framesize 352
26: dsl_scan_visitbp framesize 352
27: dsl_scan_visitbp framesize 352
28: dsl_scan_visitbp framesize 352
29: dsl_scan_visitbp framesize 352
30: dsl_scan_visitbp framesize 352
31: dsl_scan_visitdnode framesize 144
32: dsl_scan_visitbp framesize 352
33: dsl_scan_visitds framesize 144
34: dsl_scan_visitdnode framesize 144
35: dsl_scan_visitbp framesize 352
36: dsl_scan_visitds framesize 144
37: dsl_scan_visit framesize 560
38: dsl_scan_sync_state framesize 32
39: dsl_scan_sync framesize 112
40: spa_sync_version framesize 48
41: spa_sync_nvlist framesize 96
42: spa_sync_config_object framesize 432
43: spa_sync_aux_dev.part.6 framesize 112
44: spa_sync_props framesize 128
45: spa_sync framesize 208
46: spa_sync_allpools framesize 32
47: spa_sync_pass framesize 8
48: spa_syncing_txg framesize 8
49: txg_sync_thread framesize 240

frame size sum = 10552, # frames 50