On Wed, Apr 11, 2018 at 11:26:06AM -0700, Matthew Wilcox wrote:
> I had a Thought. And it seems to work:
Now I realised that slub doesn't use s_mem. That gives us more space
to use for pages/pobjects.
struct page {
unsigned long flags;
union { /* Five words */
struct { /* Page cache & anonymous pages */
struct list_head lru;
unsigned long private;
struct address_space *mapping;
pgoff_t index;
};
struct { /* Slob */
struct list_head slob_list;
int units;
};
struct { /* Slab */
struct kmem_cache *slab_cache;
void *freelist;
void *s_mem;
unsigned int active;
};
struct { /* Slub */
struct kmem_cache *slub_cache;
/* Dword boundary */
void *slub_freelist;
unsigned short inuse;
unsigned short objects:15;
unsigned short frozen:1;
struct page *next;
#ifdef CONFIG_64BIT
int pobjects;
int pages;
#endif
short int pages;
short int pobjects;
#endif
};
struct rcu_head rcu_head;
... tail pages, page tables, etc, etc ...
};
union {
atomic_t _mapcount;
unsigned int page_type;
};
atomic_t _refcount;
struct mem_cgroup *mem_cgroup;
};
> Now everybody gets 5 contiguous words to use as they want with the only
> caveat that they can't use bit 0 of the first word (PageTail).
^^^ still true ;-)
I'd want to change slob to use slob_list instead of ->lru. Or maybe even do
something radical like _naming_ the struct in the union so we don't have to
manually namespace the names of the elements.
