tdisksched.c - plan9port - [fork] Plan 9 from user space
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tdisksched.c (2107B)
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1 #include "stdinc.h"
2 #include "dat.h"
3 #include "fns.h"
4
5 ulong lasttime[2];
6 int manualscheduling;
7 int l0quantum = 120;
8 int l1quantum = 120;
9 ulong lasticachechange;
10
11 void
12 disksched(void)
13 {
14 int p, nwrite, nflush, ndirty, tdirty, toflush;
15 ulong t;
16 vlong cflush;
17 Stats *prev;
18
19 /*
20 * no locks because all the data accesses are atomic.
21 */
22 t = time(0);
23 if(manualscheduling){
24 lasticachechange = t;
25 return;
26 }
27
28 if(t-lasttime[0] < l0quantum){
29 /* level-0 disk access going on */
30 p = icachedirtyfrac();
31 if(p < IcacheFrac*5/10){ /* can wait */
32 icachesleeptime = SleepForever;
33 lasticachechange = t;
34 }else if(p > IcacheFrac*9/10){ /* can't wait */
35 icachesleeptime = 0;
36 lasticachechange = t;
37 }else if(t-lasticachechange > 60){
38 /* have minute worth of data for current rate */
39 prev = &stathist[(stattime-60+nstathist)%nstathist];
40
41 /* # entries written to index cache */
42 nwrite = stats.n[StatIcacheWrite] - prev->n[StatIcacheWrite];
43
44 /* # dirty entries in index cache */
45 ndirty = stats.n[StatIcacheDirty] - prev->n[StatIcacheDirty];
46
47 /* # entries flushed to disk */
48 nflush = nwrite - ndirty;
49
50 /* want to stay around 70% dirty */
51 tdirty = (vlong)stats.n[StatIcacheSize]*700/1000;
52
53 /* assume nflush*icachesleeptime is a constant */
54 cflush = (vlong)nflush*(icachesleeptime+1);
55
56 /* computer number entries to write in next minute */
57 toflush = nwrite + (stats.n[StatIcacheDirty] - tdirty);
58
59 /* schedule for that many */
60 if(toflush <= 0 || cflush/toflush > 100000)
61 icachesleeptime = SleepForever;
62 else
63 icachesleeptime = cflush/toflush;
64 }
65 arenasumsleeptime = SleepForever;
66 return;
67 }
68 if(t-lasttime[1] < l1quantum){
69 /* level-1 disk access (icache flush) going on */
70 icachesleeptime = 0;
71 arenasumsleeptime = SleepForever;
72 return;
73 }
74 /* no disk access going on - no holds barred*/
75 icachesleeptime = 0;
76 arenasumsleeptime = 0;
77 }
78
79 void
80 diskaccess(int level)
81 {
82 if(level < 0 || level >= nelem(lasttime)){
83 fprint(2, "bad level in diskaccess; caller=%#p\n",
84 getcallerpc(&level));
85 return;
86 }
87 lasttime[level] = time(0);
88 }