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Calculate how many threads should be run

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This commit is contained in:
Eric Fischer 2015-07-09 15:24:47 -07:00
parent 5d4ab6df1b
commit 2bdb51e995
1 changed files with 18 additions and 7 deletions
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25
tile.cc
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@ -827,21 +827,32 @@ int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpo
unlink(geomname);
}
int useful_threads = 0;
long long todo = 0;
long long along = 0;
for (j = 0; j < TEMP_FILES; j++) {
todo += geom_size[j];
printf("%d", geom_size[j] != 0);
if (geom_size[j] > 0) {
useful_threads++;
}
}
printf("\n");
// XXX Should be the number of temp files that have data,
// capped by the number of processor threads we can actually run
// or by the number of temp files divided by 4, or by
// some number larger than 4 if we are trying to skip zooms.
//
// Will need to be a power of 2 to make sharding come out right.
int threads = 1;
#define MAX_THREADS 20 // XXX Obtain from sysctl(hw.ncpu), /proc/cpuinfo, etc.
int threads = MAX_THREADS;
if (threads > TEMP_FILES / 4) {
threads = TEMP_FILES / 4;
}
// XXX is it useful to divide further if we know we are skipping
// some zoom levels? Is it faster to have fewer CPUs working on
// sharding, but more deeply, or fewer CPUs, less deeply?
if (threads > useful_threads) {
threads = useful_threads;
}
// Round down to a power of 2
threads = 1 << (int)(log(threads) / log(2));
int thread = 0;