From linux/fs/dentry.c:
struct {
int nr_dentry;
int nr_unused;
int age_limit; /* age in seconds */
int want_pages; /* pages requested by system */
int dummy[2];
} dentry_stat = {0, 0, 45, 0,};
Dentries are dynamically allocated and deallocated, and nr_dentry seems to be 0 all the time. Hence it’s safe to assume that only nr_unused, age_limit and want_pages are used. Nr_unused seems to be exactly what its name says. Age_limit is the age in seconds after which dcache entries can be reclaimed when memory is short and want_pages is nonzero when shrink_dcache_pages() has been called and the dcache isn’t pruned yet.
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