BACKPORT: 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: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit d7eac6b6e1838ef1a1400df4ec55daa34bbc855e)
Signed-off-by: Peter Kalauskas <peskal@google.com>
Bug: 112488418
Change-Id: I5b217d3cd4da57e548196658e0824d65a0cad631

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 8e74cafe9008feafa31e532e67382312a2b74e12..de4fdb599a585e510d30d23693d4c0312517c973 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -101,6 +101,16 @@ 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;
@@ -814,6 +824,8 @@ 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);
@@ -1183,6 +1195,10 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 
        generic_end_io_acct(rw, &zram->disk->part0, start_time);
 
+       zram_slot_lock(zram, index);
+       zram_accessed(zram, index);
+       zram_slot_unlock(zram, index);
+
        if (unlikely(ret < 0)) {
                if (rw == READ)
                        atomic64_inc(&zram->stats.failed_reads);

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 4c4bc6042c898f5f4e43b087e8f8cddd50098131..79c73f50a2a222b2cd49b0c160906d3b4ae564d1 100644 (file)
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -78,6 +78,7 @@ struct zram_table_entry {
                unsigned long element;
        };
        unsigned long value;
+       u64 ac_time;
 };
 
 struct zram_stats {