2.6.13 SMP on Athlon X2: nanosleep returning waay to soon, clock_gettime(CLOCK_REALTIME...) proceeding too fast
From: Frank van Maarseveen
Date: Sun Sep 04 2005 - 06:39:39 EST
After replacing the kernel on a fresh FC4 install with a stock 2.6.13
(using gcc 3.2) and my own config it appears that the clock is going too
fast: it gains at least an hour every 12 hours or so. FC4 kernel (rpm:
kernel-2.6.11-1.1369_FC4) seems ok
I tried the following from another system with reliable clock:
for i in `yes|head -100`
do
/usr/bin/time -f %e rsh system_with_buggy_clock sleep 1
done | cat -n
annotated output:
1 1.03
2 1.03
3 1.03
4 1.03
5 1.03
6 1.03
7 1.02
8 1.03
9 1.03
10 1.03
11 1.03
12 1.03
13 1.03
14 1.03
15 1.03
16 0.72 <==
17 1.03
18 1.03
19 1.03
20 1.03
21 1.03
22 1.03
23 1.03
24 1.02
25 1.03
26 1.03
27 1.03
28 1.03
29 1.03
30 1.03
31 1.03
32 1.03
33 1.03
34 0.14 <==
35 1.03
36 1.03
37 1.03
38 1.03
39 1.03
40 1.03
41 1.03
42 1.02
43 1.03
44 1.03
45 1.03
46 1.03
47 1.03
48 1.03
49 1.03
50 1.03
51 1.03
52 0.18 <==
53 1.03
54 1.03
55 1.03
56 1.03
57 1.03
58 1.03
59 1.03
60 1.02
61 1.03
62 1.03
63 1.03
64 1.04
65 1.03
66 1.03
67 1.03
68 1.03
69 1.03
70 0.13 <==
71 1.03
72 1.03
73 1.03
74 1.03
75 1.03
76 1.03
77 1.03
78 1.02
79 1.03
80 1.03
81 1.03
82 1.03
83 1.03
84 1.03
85 1.03
86 1.03
87 1.03
88 0.15 <==
89 1.03
90 1.03
91 1.03
92 1.03
93 1.03
94 1.03
95 1.03
96 1.02
97 1.03
98 1.03
99 1.03
100 1.03
I also ran the following script on the system with the unstable clock,
measuring timer interrupts per CPU as visible in /proc/interrupts:
CPU0 CPU1
0: 6741707 5860969 IO-APIC-edge timer
1: 45 10 IO-APIC-edge i8042
2: 0 0 XT-PIC cascade
8: 0 1 IO-APIC-edge rtc
14: 807745 907612 IO-APIC-edge ide0
15: 834978 871118 IO-APIC-edge ide1
17: 45336986 45939432 IO-APIC-level SysKonnect SK-98xx
18: 0 0 IO-APIC-level libata
21: 0 0 IO-APIC-level ehci_hcd:usb1, uhci_hcd:usb2, uhci_hcd:usb3, uhci_hcd:usb4, uhci_hcd:usb5
22: 0 0 IO-APIC-level VIA8237
NMI: 0 0
LOC: 12601494 12601519
ERR: 0
MIS: 0
script:
#!/bin/sh
for i in `yes|head -100`
do
s1=`cat /proc/interrupts`
sleep 1
s2=`cat /proc/interrupts`
t10=`echo "$s1" | awk '$1=="0:"{ print $2}'`
t11=`echo "$s1" | awk '$1=="0:"{ print $3}'`
t20=`echo "$s2" | awk '$1=="0:"{ print $2}'`
t21=`echo "$s2" | awk '$1=="0:"{ print $3}'`
d1=`expr $t20 - $t10`
d2=`expr $t21 - $t11`
echo $d1 + $d2 = `expr $d1 + $d2`
done | cat -n
annotated output:
CPU0 CPU1 Total
-----------------------
1 0 + 251 = 251
2 0 + 251 = 251
3 0 + 251 = 251
4 0 + 251 = 251
5 0 + 251 = 251
6 52 + 196 = 248 <== (?)
7 251 + 0 = 251
8 251 + 0 = 251
9 251 + 0 = 251
10 251 + 0 = 251
11 251 + 0 = 251
12 251 + 0 = 251
13 251 + 0 = 251
14 251 + 0 = 251
15 251 + 0 = 251
16 147 + 1 = 148 <==
17 0 + 252 = 252
18 0 + 251 = 251
19 0 + 251 = 251
20 0 + 251 = 251
21 0 + 251 = 251
22 0 + 252 = 252
23 0 + 251 = 251
24 72 + 177 = 249 <== (?)
25 252 + 0 = 252
26 252 + 0 = 252
27 252 + 0 = 252
28 252 + 0 = 252
29 252 + 0 = 252
30 252 + 0 = 252
31 252 + 0 = 252
32 253 + 0 = 253
33 253 + 0 = 253
34 118 + 2 = 120 <==
35 0 + 253 = 253
36 0 + 253 = 253
37 0 + 253 = 253
38 0 + 253 = 253
39 0 + 252 = 252
40 0 + 252 = 252
41 0 + 252 = 252
42 78 + 171 = 249 <== (?)
43 252 + 0 = 252
44 252 + 0 = 252
45 252 + 0 = 252
46 252 + 0 = 252
47 251 + 0 = 251
48 251 + 0 = 251
49 251 + 0 = 251
50 251 + 0 = 251
51 251 + 0 = 251
52 121 + 1 = 122 <==
53 0 + 251 = 251
54 0 + 251 = 251
55 0 + 251 = 251
56 0 + 251 = 251
57 0 + 251 = 251
58 0 + 251 = 251
59 0 + 251 = 251
60 69 + 179 = 248 <== (?)
61 251 + 0 = 251
62 251 + 0 = 251
63 251 + 0 = 251
64 251 + 0 = 251
65 251 + 0 = 251
66 251 + 0 = 251
67 251 + 0 = 251
68 251 + 0 = 251
69 251 + 0 = 251
70 130 + 1 = 131 <==
71 0 + 252 = 252
72 0 + 252 = 252
73 0 + 252 = 252
74 0 + 252 = 252
75 0 + 252 = 252
76 0 + 252 = 252
77 0 + 252 = 252
78 77 + 172 = 249 <== (?)
79 253 + 0 = 253
80 253 + 0 = 253
81 253 + 0 = 253
82 253 + 0 = 253
83 253 + 0 = 253
84 253 + 0 = 253
85 252 + 0 = 252
86 252 + 0 = 252
87 252 + 0 = 252
88 112 + 2 = 114 <==
89 0 + 252 = 252
90 0 + 252 = 252
91 0 + 252 = 252
92 0 + 252 = 252
93 0 + 252 = 252
94 0 + 252 = 252
95 0 + 251 = 251
96 0 + 251 = 251
97 0 + 251 = 251
98 53 + 195 = 248 <== (?)
99 251 + 0 = 251
100 251 + 0 = 251
The hangcheck timer goes off when configured.
--
Frank
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