Hi list!

I'm wondering about the usage of frontswap and cleancache. Now that all
pieces are in place in kernel-3.5, is it actually used?

I've found references to cleancache and frontswap in several source
files of the kernel (ext4, swapfile, page_io, ...).
/sys/kernel/mm/zcache is also present but seems to indicate no usage at
all. Content attached below.

So, what is the state of all this? Should it work? Does it work? Am I
missing a kernel parameter or something?

Content of /sys/kernel/mm/zcache:
compress_poor: 0
curr_obj_count: 0
curr_obj_count_max: 0
curr_objnode_count: 0
curr_objnode_count_max: 0
evicted_buddied_pages: 0
evicted_raw_pages: 0
evicted_unbuddied_pages: 0
failed_alloc: 0
failed_eph_puts: 0
failed_get_free_pages: 0
failed_pers_puts: 0
flobj_found: 0
flobj_total: 0
flush_found: 0
flush_total: 0
mean_compress_poor: 0
put_to_flush: 0
zbpg_unused_list_count: 0
zbud_buddied_count: 0
zbud_cumul_chunk_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 <=21:0 <=32:0 <=42:0, mean:0
zbud_cumul_zbytes: 0
zbud_cumul_zpages: 0
zbud_curr_raw_pages: 0
zbud_curr_zbytes: 0
zbud_curr_zpages: 0
zbud_unbuddied_list_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 zv_cumul_dist_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 mean:0
zv_curr_dist_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
mean:0
zv_max_mean_zsize: 2560
zv_max_zsize: 3584
zv_page_count_policy_percent: 75

Thanks in advance,
Florian Philipp