----- Am 1. Mai 2018 um 5:38 schrieb Chris Johns chr...@rtems.org:
> On 30/04/2018 20:05, Sebastian Huber wrote:
>>> 3) Investigate the importance of live tracing functionality and addition of
>>> kernel level tracing. I will design both possibilities and decide which one
>>> to
>>> work on by the end of phase 1 of my evaluation.
>>
>> I work currently on a new low level infrastructure to support gathering of
>> thread (create, delete, terminate, switch) and interrupt (entry, exit)
>> events.
>> Similar to the capture engine, but with less overhead.
>
> Why not improve the existing code?
There are some problems with the capture engine in terms of data structures,
synchronization, timestamping and the API.
* The sizeof(rtems_capture_record) is 20 bytes, I use only 12 bytes (16 on a
64-bit machine). I want to record high frequency events, so this 33% reduction
makes a difference.
* Synchronization is done via atomic read-modify-write operations (ticket
locks). The alternative implementation simply uses interrupt disable/enable.
* The timestamps use 64-bits and by default
rtems_clock_get_uptime_nanoseconds() is used. This function has a high overhead
for this purpose. The alternative implementation uses a 32-bit timestamp and
the CPU counter. The uptime and CPU counter values are synchronized via a
periodic event.
* Variable size records need more logic (branches) than fixed size records.
>
> Does this create a new interface and management structure?
> Do you have the requirements for this design documented anywhere?
There is not much to design. I just need a single producer single consumer
queue (ring buffer) per processor. Here is the assembler code of the main
function:
typedef CPU_Uint32ptr rtems_record_data;
#define RTEMS_RECORD_EVENT_EXTRA( domain, extra ) \
( ( ( extra ) << 6 ) | ( domain ) )
typedef enum {
#define RECORD_EVENT_SYSTEM_0( extra ) \
RTEMS_RECORD_EVENT_EXTRA( 0, extra )
RTEMS_RECORD_EVENT_OVERFLOW = RECORD_EVENT_SYSTEM_0( 0 ),
RTEMS_RECORD_EVENT_UPTIME_LOW = RECORD_EVENT_SYSTEM_0( 1 ),
RTEMS_RECORD_EVENT_UPTIME_HIGH = RECORD_EVENT_SYSTEM_0( 2 ),
RTEMS_RECORD_EVENT_PROCESSOR = RECORD_EVENT_SYSTEM_0( 3 ),
RTEMS_RECORD_EVENT_THREAD_CREATED = RECORD_EVENT_SYSTEM_0( 4 ),
RTEMS_RECORD_EVENT_THREAD_CREATED_BY = RECORD_EVENT_SYSTEM_0( 5 ),
RTEMS_RECORD_EVENT_THREAD_SWITCH = RECORD_EVENT_SYSTEM_0( 6 ),
RTEMS_RECORD_EVENT_THREAD_DELETED = RECORD_EVENT_SYSTEM_0( 7 ),
RTEMS_RECORD_EVENT_THREAD_DELETED_BY = RECORD_EVENT_SYSTEM_0( 8 ),
RTEMS_RECORD_EVENT_THREAD_TERMINATED = RECORD_EVENT_SYSTEM_0( 9 ),
RTEMS_RECORD_EVENT_INTERUPT_INSTALL = RECORD_EVENT_SYSTEM_0( 10 ),
RTEMS_RECORD_EVENT_INTERUPT_REMOVE = RECORD_EVENT_SYSTEM_0( 11 ),
RTEMS_RECORD_EVENT_INTERUPT_BEGIN = RECORD_EVENT_SYSTEM_0( 12 ),
RTEMS_RECORD_EVENT_INTERUPT_END = RECORD_EVENT_SYSTEM_0( 13 ),
/* Reserved system event domains */
RTEMS_RECORD_EVENT_SYSTEM_0 = 0,
RTEMS_RECORD_EVENT_SYSTEM_1,
RTEMS_RECORD_EVENT_SYSTEM_2,
RTEMS_RECORD_EVENT_SYSTEM_3,
RTEMS_RECORD_EVENT_SYSTEM_4,
RTEMS_RECORD_EVENT_SYSTEM_5,
RTEMS_RECORD_EVENT_SYSTEM_6,
RTEMS_RECORD_EVENT_SYSTEM_7,
RTEMS_RECORD_EVENT_SYSTEM_8,
RTEMS_RECORD_EVENT_SYSTEM_9,
RTEMS_RECORD_EVENT_SYSTEM_10,
RTEMS_RECORD_EVENT_SYSTEM_11,
RTEMS_RECORD_EVENT_SYSTEM_12,
RTEMS_RECORD_EVENT_SYSTEM_13,
RTEMS_RECORD_EVENT_SYSTEM_14,
RTEMS_RECORD_EVENT_SYSTEM_15,
/* User event domains */
RTEMS_RECORD_EVENT_USER_0,
RTEMS_RECORD_EVENT_USER_1,
RTEMS_RECORD_EVENT_USER_2,
RTEMS_RECORD_EVENT_USER_3,
RTEMS_RECORD_EVENT_USER_4,
RTEMS_RECORD_EVENT_USER_5,
RTEMS_RECORD_EVENT_USER_6,
RTEMS_RECORD_EVENT_USER_7,
RTEMS_RECORD_EVENT_USER_8,
RTEMS_RECORD_EVENT_USER_9,
RTEMS_RECORD_EVENT_USER_10,
RTEMS_RECORD_EVENT_USER_11,
RTEMS_RECORD_EVENT_USER_12,
RTEMS_RECORD_EVENT_USER_13,
RTEMS_RECORD_EVENT_USER_14,
RTEMS_RECORD_EVENT_USER_15,
RTEMS_RECORD_EVENT_USER_16,
RTEMS_RECORD_EVENT_USER_17,
RTEMS_RECORD_EVENT_USER_18,
RTEMS_RECORD_EVENT_USER_19,
RTEMS_RECORD_EVENT_USER_20,
RTEMS_RECORD_EVENT_USER_21,
RTEMS_RECORD_EVENT_USER_22,
RTEMS_RECORD_EVENT_USER_23,
RTEMS_RECORD_EVENT_USER_24,
RTEMS_RECORD_EVENT_USER_25,
RTEMS_RECORD_EVENT_USER_26,
RTEMS_RECORD_EVENT_USER_27,
RTEMS_RECORD_EVENT_USER_28,
RTEMS_RECORD_EVENT_USER_29,
RTEMS_RECORD_EVENT_USER_30,
RTEMS_RECORD_EVENT_USER_31,
RTEMS_RECORD_EVENT_USER_32,
RTEMS_RECORD_EVENT_USER_33,
RTEMS_RECORD_EVENT_USER_34,
RTEMS_RECORD_EVENT_USER_35,
RTEMS_RECORD_EVENT_USER_36,
RTEMS_RECORD_EVENT_USER_37,
RTEMS_RECORD_EVENT_USER_38,
RTEMS_RECORD_EVENT_USER_39,
RTEMS_RECORD_EVENT_USER_40,
RTEMS_RECORD_EVENT_USER_41,
RTEMS_RECORD_EVENT_USER_42,
RTEMS_RECORD_EVENT_USER_43,
RTEMS_RECORD_EVENT_USER_44,
RTEMS_RECORD_EVENT_USER_45,
RTEMS_RECORD_EVENT_USER_46,
RTEMS_RECORD_EVENT_USER_47,
RTEMS_RECORD_EVENT_LAST = 0xffffffff
} rtems_record_event;
void rtems_record_produce( rtems_record_event event, rtems_record_data data );
00000000 <rtems_record_produce>:
0: 7c a0 00 a6 mfmsr r5
4: 7c 00 01 46 wrteei 0
8: 7d 6e 82 a6 mfspr r11,526
c: 7d 30 42 a6 mfsprg r9,0
10: 81 09 02 b0 lwz r8,688(r9)
14: 80 e8 00 00 lwz r7,0(r8)
18: 81 28 00 04 lwz r9,4(r8)
1c: 80 c8 00 08 lwz r6,8(r8)
20: 39 29 ff ff addi r9,r9,-1
24: 7d 27 48 50 subf r9,r7,r9
28: 7d 29 30 38 and r9,r9,r6
2c: 2b 89 00 01 cmplwi cr7,r9,1
This is the only branch in the function:
30: 41 dd 00 40 bgt- cr7,70 <rtems_record_produce+0x70>
34: 54 ea 08 3c rlwinm r10,r7,1,0,30
38: 38 60 00 00 li r3,0
3c: 7d 4a 3a 14 add r10,r10,r7
40: 7d 27 4a 14 add r9,r7,r9
44: 55 4a 10 3a rlwinm r10,r10,2,0,29
48: 7d 29 30 38 and r9,r9,r6
4c: 7d 48 52 14 add r10,r8,r10
50: 90 6a 00 0c stw r3,12(r10)
54: 91 6a 00 10 stw r11,16(r10)
58: 90 8a 00 14 stw r4,20(r10)
5c: 7c 20 04 ac lwsync
60: 91 28 00 00 stw r9,0(r8)
64: 7c a0 01 06 wrtee r5
68: 4e 80 00 20 blr
Only 27 instructions in the common path (no ring buffer overflow, overflows are
special events).
6c: 60 00 00 00 nop
70: 54 ea 08 3c rlwinm r10,r7,1,0,30
74: 39 20 00 01 li r9,1
78: 7d 4a 3a 14 add r10,r10,r7
7c: 7d 27 4a 14 add r9,r7,r9
80: 55 4a 10 3a rlwinm r10,r10,2,0,29
84: 7d 29 30 38 and r9,r9,r6
88: 7d 48 52 14 add r10,r8,r10
8c: 90 6a 00 0c stw r3,12(r10)
90: 91 6a 00 10 stw r11,16(r10)
94: 90 8a 00 14 stw r4,20(r10)
98: 7c 20 04 ac lwsync
9c: 91 28 00 00 stw r9,0(r8)
a0: 7c a0 01 06 wrtee r5
a4: 4e 80 00 20 blr
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