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Commit 6a83472c authored by Minchan Kim's avatar Minchan Kim Committed by Peter Kalauskas
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UPSTREAM: zram: record accessed second 

zRam as swap is useful for small memory device.  However, swap means
those pages on zram are mostly cold pages due to VM's LRU algorithm.
Especially, once init data for application are touched for launching,
they tend to be not accessed any more and finally swapped out.  zRAM can
store such cold pages as compressed form but it's pointless to keep in
memory.  Better idea is app developers free them directly rather than
remaining them on heap.

This patch records last access time of each block of zram so that With
upcoming zram memory tracking, it could help userspace developers to
reduce memory footprint.

Link: http://lkml.kernel.org/r/20180416090946.63057-4-minchan@kernel.org


Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Reviewed-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit d7eac6b6e1838ef1a1400df4ec55daa34bbc855e)
Signed-off-by: default avatarPeter Kalauskas <peskal@google.com>
Bug: 112488418
Change-Id: I34f5de4dd58ba54bb1cc85d558e60231b2810780
parent 97ceebc2

drivers/block/zram/zram_drv.c

+16 −0
Original line number Diff line number Diff line
@@ -102,6 +102,16 @@ static inline void zram_set_element(struct zram *zram, u32 index, 
	zram->table[index].element = element;

}



static void zram_accessed(struct zram *zram, u32 index)

{

	zram->table[index].ac_time = sched_clock();

}



static void zram_reset_access(struct zram *zram, u32 index)

{

	zram->table[index].ac_time = 0;

}



static unsigned long zram_get_element(struct zram *zram, u32 index)

{

	return zram->table[index].element;
@@ -799,6 +809,8 @@ static void zram_free_page(struct zram *zram, size_t index) 
{

	unsigned long handle;



	zram_reset_access(zram, index);



	if (zram_test_flag(zram, index, ZRAM_HUGE)) {

		zram_clear_flag(zram, index, ZRAM_HUGE);

		atomic64_dec(&zram->stats.huge_pages);
@@ -1170,6 +1182,10 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index, 


	generic_end_io_acct(q, rw_acct, &zram->disk->part0, start_time);



	zram_slot_lock(zram, index);

	zram_accessed(zram, index);

	zram_slot_unlock(zram, index);



	if (unlikely(ret < 0)) {

		if (!is_write)

			atomic64_inc(&zram->stats.failed_reads);

drivers/block/zram/zram_drv.h

+1 −0
Original line number Diff line number Diff line
@@ -78,6 +78,7 @@ struct zram_table_entry { 
		unsigned long element;

	};

	unsigned long value;

	u64 ac_time;

};



struct zram_stats {