[RFC 2/3] arm64: refactor save_stack_trace()

[Jungseok Lee]

On Jul 17, 2015, at 12:31 AM, Steven Rostedt wrote:
> On Fri, 17 Jul 2015 00:01:25 +0900
> Jungseok Lee <jungseoklee85 at 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.

Thanks for x86 data. It's really helpful!

> 
>> 
>> 		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.

Totally agree.

Best Regards
Jungseok Lee