minix/lib/libminixfs/cache.c

61 lines
1.5 KiB
C
Raw Normal View History

#define _SYSTEM
#include <minix/libminixfs.h>
#include <minix/dmap.h>
#include <minix/u64.h>
#include <minix/sysutil.h>
#include <sys/param.h>
#include <errno.h>
u32_t fs_bufs_heuristic(int minbufs, u32_t btotal, u32_t bfree,
int blocksize, dev_t majordev)
{
struct vm_stats_info vsi;
int bufs;
u32_t kbytes_used_fs, kbytes_total_fs, kbcache, kb_fsmax;
u32_t kbytes_remain_mem, bused;
bused = btotal-bfree;
/* but we simply need minbufs no matter what, and we don't
* want more than that if we're a memory device
*/
if(majordev == MEMORY_MAJOR) {
return minbufs;
}
/* set a reasonable cache size; cache at most a certain
* portion of the used FS, and at most a certain %age of remaining
* memory
*/
if((vm_info_stats(&vsi) != OK)) {
bufs = 1024;
printf("fslib: heuristic info fail: default to %d bufs\n", bufs);
return bufs;
}
kbytes_remain_mem = div64u(mul64u(vsi.vsi_free, vsi.vsi_pagesize), 1024);
/* check fs usage. */
kbytes_used_fs = div64u(mul64u(bused, blocksize), 1024);
kbytes_total_fs = div64u(mul64u(btotal, blocksize), 1024);
/* heuristic for a desired cache size based on FS usage;
* but never bigger than half of the total filesystem
*/
kb_fsmax = sqrt_approx(kbytes_used_fs)*40;
kb_fsmax = MIN(kb_fsmax, kbytes_total_fs/2);
/* heuristic for a maximum usage - 10% of remaining memory */
kbcache = MIN(kbytes_remain_mem/10, kb_fsmax);
bufs = kbcache * 1024 / blocksize;
/* but we simply need MINBUFS no matter what */
if(bufs < minbufs)
bufs = minbufs;
return bufs;
}