zipf: cap range calculation at 10M

[fio.git] / lib / zipf.c

diff --git a/lib/zipf.c b/lib/zipf.c
index c7bb8a80799ce88adedae2a139dd3ea5e59a30d4..c348c9c3fd5cbac2eb2985092157a4e29dd72902 100644 (file)
--- a/lib/zipf.c
+++ b/lib/zipf.c
@@ -10,82 +10,25 @@
 #include "zipf.h"
 #include "../minmax.h"
 #include "../hash.h"
-#include "../os/os.h"
 
-struct fio_zipf_disk {
-       uint64_t ver_magic;
-       uint64_t nranges;
-       uint64_t zetan;
-};
-
-#define FIO_ZIPF_DISK_MAGIC    0x7a697066
-#define FIO_ZIPF_DISK_VER      1
-#define FIO_ZIPF_MAGIC         ((FIO_ZIPF_DISK_MAGIC << 16) | FIO_ZIPF_DISK_VER)
-
-static void write_zipf(struct zipf_state *zs)
-{
-       struct fio_zipf_disk f;
-       char tmp[80];
-       int fd;
-
-       sprintf(tmp, "fio.zipf.%f.%llu", zs->theta, (unsigned long long) zs->nranges);
-       fd = open(tmp, O_CREAT | O_WRONLY, 0644);
-       if (fd == -1)
-               return;
-
-       f.ver_magic = __cpu_to_le64(FIO_ZIPF_MAGIC);
-       f.nranges = __cpu_to_le64(zs->nranges);
-       f.zetan = __cpu_to_le64(fio_double_to_uint64(zs->zetan));
-       if (write(fd, &f, sizeof(f)) != sizeof(f))
-               unlink(tmp);
-
-       close(fd);
-}
+#define ZIPF_MAX_GEN   10000000
 
 static void zipf_update(struct zipf_state *zs)
 {
+       unsigned long to_gen;
        unsigned int i;
 
        log_info("fio: generating zetan for theta=%f, ranges=%lu\n", zs->theta, zs->nranges);
 
-       for (i = 0; i < zs->nranges; i++)
-               zs->zetan += pow(1.0 / (double) (i + 1), zs->theta);
+       /*
+        * It can become very costly to generate long sequences. Just cap it at
+        * 10M max, that should be doable in 1-2s on even slow machines. Precision
+        * will take a slight hit, but nothing major.
+        */
+       to_gen = min(zs->nranges, ZIPF_MAX_GEN);
 
-       write_zipf(zs);
-}
-
-static void zipf_load_gen_zeta(struct zipf_state *zs)
-{
-       struct fio_zipf_disk f;
-       char tmp[80];
-       int fd;
-
-       sprintf(tmp, "fio.zipf.%f.%llu", zs->theta, (unsigned long long) zs->nranges);
-       fd = open(tmp, O_RDONLY);
-       if (fd == -1) {
-punt:
-               zipf_update(zs);
-               return;
-       }
-
-       if (read(fd, &f, sizeof(f)) != sizeof(f)) {
-               close(fd);
-               goto punt;
-       }
-
-       close(fd);
-
-       f.ver_magic = le64_to_cpu(f.ver_magic);
-       f.nranges = le64_to_cpu(f.nranges);
-       f.zetan = le64_to_cpu(f.zetan);
-
-       if (f.ver_magic != FIO_ZIPF_MAGIC) {
-               unlink(tmp);
-               goto punt;
-       }
-
-       zs->zetan = fio_uint64_to_double(f.zetan);
-       zs->nranges = f.nranges;
+       for (i = 0; i < to_gen; i++)
+               zs->zetan += pow(1.0 / (double) (i + 1), zs->theta);
 }
 
 static void shared_rand_init(struct zipf_state *zs, unsigned long nranges,
@@ -106,7 +49,7 @@ void zipf_init(struct zipf_state *zs, unsigned long nranges, double theta,
        zs->theta = theta;
        zs->zeta2 = pow(1.0, zs->theta) + pow(0.5, zs->theta);
 
-       zipf_load_gen_zeta(zs);
+       zipf_update(zs);
 }
 
 unsigned long long zipf_next(struct zipf_state *zs)