Jörn Engel wrote:
xfs is quite interesting. No single function is particularly
stack-hungry, but the sheer depth of the call path adds up. Nathan,
can you see if some bytes can be saved here and there?
3k is not really bad yet, I just like to keep 1k of headroom for
surprises like an extra int foo[256] in a structure.
Are you doing some form of call chain analysis to arrive
at this stack?
Actually this one is impossible, the function xfs_bmapi is
confusing you analyser, it is used for read and write
calls to map from file offsets to disk blocks. The path
you chased down from xfs_bmapi is doing a realtime
allocation, the swapext call does not do allocations,
it is in this case looking up the contents of an acl
for a permission check - xfs_bmapi in this case will
not call much of anything.
The bmapi path you did follow, for an allocation in a
realtime file, is doing a read of the realtime bitmap
inode which holds the layout of the realtime component
of the filesystem.
Once it gets to schedule it is a little out of XFS's hands what
happens, or which stack is actually in use. I think the
path you followed out of schedule is the cleanup of the
audit structure of a dead process - it is the one doing
the panicing here. An xfs call into schedule to wait for
I/O will not be going down that path.
I think you have to be careful looking at these call chains.
Steve
stackframes for call path too long (3064):
size function
144 xfs_ioctl
328 xfs_swapext
0 xfs_iaccess
16 xfs_acl_iaccess
104 xfs_attr_fetch
0 xfs_attr_node_get
28 xfs_da_node_lookup_int
68 xfs_dir2_leafn_lookup_int
0 xfs_da_read_buf
288 xfs_bmapi
52 xfs_rtpick_extent
24 xfs_trans_iget
32 xfs_iget
32 xfs_iread
72 xfs_itobp
60 xfs_imap
84 xfs_dilocate
0 xfs_inobt_lookup_le
16 xfs_inobt_increment
28 xfs_btree_readahead_core
20 xfs_btree_reada_bufl
12 pagebuf_readahead
16 pagebuf_get
0 pagebuf_iostart
0 xfs_bdstrat_cb
68 pagebuf_iorequest
0 pagebuf_iodone
0 pagebuf_iodone_work
0 pagebuf_rele
0 preempt_schedule
84 schedule
16 __put_task_struct
20 audit_free
36 audit_log_start
16 __kmalloc
0 __get_free_pages
28 __alloc_pages
284 try_to_free_pages
0 out_of_memory
0 mmput
16 exit_aio
0 __put_ioctx
16 do_munmap
0 split_vma
36 vma_adjust
0 fput
0 __fput
0 locks_remove_flock
12 panic
0 sys_sync
0 sync_inodes
308 sync_inodes_sb
0 do_writepages
128 mpage_writepages
4 write_boundary_block
0 ll_rw_block
28 submit_bh
0 bio_alloc
88 mempool_alloc
256 wakeup_bdflush
20 pdflush_operation
0 printk
16 release_console_sem
16 __wake_up
0 printk
0 vscnprintf
32 vsnprintf
112 number
Jörn
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