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SubjectRe: [RFC 2/3] arm64: refactor save_stack_trace()
On Fri, 17 Jul 2015 00:01:25 +0900
Jungseok Lee <jungseoklee85@gmail.com> wrote:

> I've gathered stack tracer data with your update.
>
> 1) stack_trace
> Depth Size Location (35 entries)
> ----- ---- --------
> 0) 4424 16 put_cpu_partial+0x28/0x1d0
> 1) 4408 80 get_partial_node.isra.64+0x13c/0x344
> 2) 4328 256 __slab_alloc.isra.65.constprop.67+0xd8/0x37c
> 3) 4072 32 kmem_cache_alloc+0x258/0x294
> 4) 4040 304 __alloc_skb+0x48/0x180
> 5) 3736 96 alloc_skb_with_frags+0x74/0x234
> 6) 3640 112 sock_alloc_send_pskb+0x1d0/0x294
> 7) 3528 160 sock_alloc_send_skb+0x44/0x54
> 8) 3368 64 __ip_append_data.isra.40+0x78c/0xb48
> 9) 3304 224 ip_append_data.part.42+0x98/0xe8
> 10) 3080 112 ip_append_data+0x68/0x7c
> 11) 2968 96 icmp_push_reply+0x7c/0x144
> 12) 2872 96 icmp_send+0x3c0/0x3c8
> 13) 2776 192 __udp4_lib_rcv+0x5b8/0x684
> 14) 2584 96 udp_rcv+0x2c/0x3c
> 15) 2488 32 ip_local_deliver+0xa0/0x224
> 16) 2456 48 ip_rcv+0x360/0x57c
> 17) 2408 64 __netif_receive_skb_core+0x4d0/0x80c
> 18) 2344 128 __netif_receive_skb+0x24/0x84
> 19) 2216 32 process_backlog+0x9c/0x15c
> 20) 2184 80 net_rx_action+0x1ec/0x32c
> 21) 2104 160 __do_softirq+0x114/0x2f0
> 22) 1944 128 do_softirq+0x60/0x68
> 23) 1816 32 __local_bh_enable_ip+0xb0/0xd4
> 24) 1784 32 ip_finish_output+0x1f4/0xabc
> 25) 1752 96 ip_output+0xf0/0x120
> 26) 1656 64 ip_local_out_sk+0x44/0x54
> 27) 1592 32 ip_send_skb+0x24/0xbc
> 28) 1560 48 udp_send_skb+0x1b4/0x2f4
> 29) 1512 80 udp_sendmsg+0x2a8/0x7a0
> 30) 1432 272 inet_sendmsg+0xa0/0xd0
> 31) 1160 48 sock_sendmsg+0x30/0x78
> 32) 1112 32 ___sys_sendmsg+0x15c/0x26c
> 33) 1080 400 __sys_sendmmsg+0x94/0x180
> 34) 680 320 SyS_sendmmsg+0x38/0x54
> 35) 360 360 el0_svc_naked+0x20/0x28
>
> 2) stack_max_size
> 4504

Strange, on x86 I have this (with my patch applied):

Depth Size Location (39 entries)
----- ---- --------
0) 3704 64 _raw_spin_lock+0x5/0x30
1) 3640 200 get_partial_node.isra.80+0x54/0x1da
2) 3440 208 __slab_alloc.isra.82+0x199/0x3f7
3) 3232 80 kmem_cache_alloc+0x151/0x160
4) 3152 16 mempool_alloc_slab+0x15/0x20
5) 3136 128 mempool_alloc+0x58/0x150
6) 3008 16 scsi_sg_alloc+0x42/0x50
7) 2992 112 __sg_alloc_table+0x10b/0x150
8) 2880 48 scsi_alloc_sgtable+0x43/0x80
9) 2832 32 scsi_init_sgtable+0x2b/0x70
10) 2800 80 scsi_init_io+0x59/0x1e0
11) 2720 128 sd_init_command+0x66/0xd80
12) 2592 24 scsi_setup_cmnd+0xa9/0x160
13) 2568 88 scsi_prep_fn+0x7d/0x160
14) 2480 48 blk_peek_request+0x168/0x2a0
15) 2432 112 scsi_request_fn+0x3f/0x610
16) 2320 8 __blk_run_queue+0x37/0x50
17) 2312 104 queue_unplugged+0x41/0xe0
18) 2208 112 blk_flush_plug_list+0x1b7/0x1e0
19) 2096 80 blk_queue_bio+0x257/0x340
20) 2016 48 generic_make_request+0xb1/0xf0
21) 1968 96 submit_bio+0x76/0x130
22) 1872 48 submit_bh_wbc.isra.35+0x10b/0x140
23) 1824 112 __block_write_full_page.constprop.40+0x188/0x310
24) 1712 64 block_write_full_page+0xdd/0x130
25) 1648 16 blkdev_writepage+0x18/0x20
26) 1632 8 __writepage+0x17/0x40
27) 1624 312 write_cache_pages+0x21e/0x480
28) 1312 96 generic_writepages+0x4a/0x70
29) 1216 16 do_writepages+0x20/0x30
30) 1200 96 __writeback_single_inode+0x45/0x350
31) 1104 176 writeback_sb_inodes+0x218/0x3d0
32) 928 80 __writeback_inodes_wb+0x8c/0xc0
33) 848 128 wb_writeback+0x239/0x2c0
34) 720 192 wb_workfn+0x24b/0x460
35) 528 80 process_one_work+0x14b/0x430
36) 448 128 worker_thread+0x117/0x460
37) 320 144 kthread+0xc9/0xe0
38) 176 176 ret_from_fork+0x3f/0x70

# cat /debug/tracing/stack_max_size
3704


>
> In case of the number of entries, the following diff might be needed
> as I suggested in the previous reply. ;)
>
> ----8<----
>
> @@ -330,7 +333,7 @@ static int t_show(struct seq_file *m, void *v)
> seq_printf(m, " Depth Size Location"
> " (%d entries)\n"
> " ----- ---- --------\n",
> - max_stack_trace.nr_entries - 1);
> + max_stack_trace.nr_entries);

This would break x86.

>
> if (!stack_tracer_enabled && !max_stack_size)
> print_disabled(m);
>
> ----8<----
>
> However, 80-byte gap still appears.

This seems to be specific to your arch.

>
> Since max_stack_trace.skip is 3 in your update, save_stack_trace in arm64
> should be refactored to align with this value.
>
> max_stack_trace.skip should be set to 4 if AKASHI's [RFC 2/3] patch is merged.
> However, arch code is supposed to follow generic framework's rule in this case.
> Isn't it?
>

yeah, you don't want to update the skip level. It should just work.

I'll run this on my powerpc box and see if it shows something
different. If I have to, I'll even boot up my arm (not 64) board and
try it there.

-- Steve


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