6.5 Expanded Process IDs

6.5 Expanded Process IDs

You might be wondering, "What do expanded process IDs have to do with CDSLs and the file system hierarchy?" Nothing really, but we thought you might be interested in this bit of information and chose to offer it here.

Process IDs have been expanded to a 32-bit integer beginning in Tru64 UNIX version 5.0 (although it appears that the maximum value is 2147483647 which is actually 31-bits). In a standalone environment, you will not see any appreciable difference; for instance PID 0 is still [kernel_idle] and PID 1 is still the init daemon. The PID structure in a TruCluster environment, however, is defined to provide a unique range of process IDs (524288 PIDs/member) and is defined as follows:

1. Process ID (19-bits)

2. Member ID (8-bits)

3. Sequence Number (4-bits) – currently unused.

4. Sign-bit (1-bit) – this is reserved for future use.

The PID structure is defined in /usr/include/sys/types.h. The initial PID for each member is shown in Table 6-6.

Table 6-6: PID Range by Member

PID Range by Member ID
Memberid 219
Member ID	PID	Member ID	PID	Member ID	PID
1	524288	22	11534336	43	22544384
2	1048576	23	12058624	44	23068672
3	1572864	24	12582912	45	23592960
4	2097152	25	13107200	46	24617248
5	26211440	26	13631488	47	24641536
6	3145728	27	14155776	48	25165824
7	3670016	28	14680064	49	25690112
8	4194304	29	15204352	50	26214400
9	4718592	30	15728640	51	26738688
10	5242880	31	16252928	52	27262976
11	5767168	32	16777216	53	27787264
12	6291456	33	17301504	54	28311552
13	6815744	34	17825792	55	28835840
14	7340032	35	18350080	56	29360128
15	7864320	36	18874368	57	29884416
16	8388608	37	19398656	58	30408704
17	8912896	38	19922944	59	30932992
18	9437184	39	20447232	60	31457280
19	9961472	40	20971520	61	31981568
20	10485760	41	21495808	62	32505856
21	11010048	42	22020096	63	33030144

Let's take a closer look at the PID of the init daemon on a cluster to explore how the PID structure in a cluster affects the PID. On member1, the PID for init would be 524589.

 # sysconfig -q generic memberid generic: memberid = 1 

 # ps -eo pid,command | grep "/sbin/init" | grep -v grep 524289 /sbin/init -a 

If we convert the PID from decimal to binary, we can see the how the PID is composed.

 # perl -e 'printf ("%032b\n", 524289);' 00000000000010000000000000000001 

Figure 6-6 shows the bit field breakout.

Figure 6-6: PID Structure Illustrated