ref: 347bb2a7a7110e55debd5ebe57ba03bbe315c5ba
dir: /sys/src/cmd/venti/srv/disksched.c/
#include "stdinc.h" #include "dat.h" #include "fns.h" ulong lasttime[2]; int manualscheduling; int l0quantum = 120; int l1quantum = 120; ulong lasticachechange; void disksched(void) { int p, nwrite, nflush, ndirty, tdirty, toflush; ulong t; vlong cflush; Stats *prev; /* * no locks because all the data accesses are atomic. */ t = time(0); if(manualscheduling){ lasticachechange = t; return; } if(t-lasttime[0] < l0quantum){ /* level-0 disk access going on */ p = icachedirtyfrac(); if(p < IcacheFrac*5/10){ /* can wait */ icachesleeptime = SleepForever; lasticachechange = t; }else if(p > IcacheFrac*9/10){ /* can't wait */ icachesleeptime = 0; lasticachechange = t; }else if(t-lasticachechange > 60){ /* have minute worth of data for current rate */ prev = &stathist[(stattime-60+nstathist)%nstathist]; /* # entries written to index cache */ nwrite = stats.n[StatIcacheWrite] - prev->n[StatIcacheWrite]; /* # dirty entries in index cache */ ndirty = stats.n[StatIcacheDirty] - prev->n[StatIcacheDirty]; /* # entries flushed to disk */ nflush = nwrite - ndirty; /* want to stay around 70% dirty */ tdirty = (vlong)stats.n[StatIcacheSize]*700/1000; /* assume nflush*icachesleeptime is a constant */ cflush = (vlong)nflush*(icachesleeptime+1); /* computer number entries to write in next minute */ toflush = nwrite + (stats.n[StatIcacheDirty] - tdirty); /* schedule for that many */ if(toflush <= 0 || cflush/toflush > 100000) icachesleeptime = SleepForever; else icachesleeptime = cflush/toflush; } arenasumsleeptime = SleepForever; return; } if(t-lasttime[1] < l1quantum){ /* level-1 disk access (icache flush) going on */ icachesleeptime = 0; arenasumsleeptime = SleepForever; return; } /* no disk access going on - no holds barred*/ icachesleeptime = 0; arenasumsleeptime = 0; } void diskaccess(int level) { if(level < 0 || level >= nelem(lasttime)){ fprint(2, "bad level in diskaccess; caller=%#p\n", getcallerpc(&level)); return; } lasttime[level] = time(0); }