If the length of the compressed page is greater than 75% of the PAGE_SIZE, then the page is stored uncompressed in zram space. Zram space utilization is improved if the threshold is 80%(5 compressed pages can be stored in 4 pages).
If the compressed length is greater than 3068 and less than 3261, pages still can be stored in compressed form in zs_malloc class 3264. Currently these compressed pages belong to 4096 zs malloc class. Tested on ARM: Before Patch: class size obj_allocated obj_used pages_used 190 3072 3820 3819 2865 202 3264 65 63 52 254 4096 11791 11791 11791 Total 65604 64616 29504 After Patch: class size obj_allocated obj_used pages_used 190 3072 4244 4243 3183 202 3264 1500 1499 1200 254 4096 6306 6306 6306 Total 65983 64896 26628 Signed-off-by: Gopi Sai Teja <gopi...@samsung.com> --- drivers/block/zram/zram_drv.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index 5ece255..f7d9ddd 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -31,8 +31,12 @@ static const unsigned max_num_devices = 32; /* * Pages that compress to size greater than this are stored * uncompressed in memory. + * 16 is zsmalloc class interval and unsigned long is extra memory + * used by zsmalloc to store metadata. */ -static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; + +static const size_t max_zpage_size = round_down((PAGE_SIZE / 5 * 4), 16) + - sizeof(unsigned long); /* * NOTE: max_zpage_size must be less than or equal to: -- 1.9.1
