The patch titled
Subject: zram: record accessed second
has been added to the -mm tree. Its filename is
zram-record-accessed-second.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zram-record-accessed-second.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zram-record-accessed-second.patch
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------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 16 ++++++++++++++++
drivers/block/zram/zram_drv.h | 1 +
2 files changed, 17 insertions(+)
diff -puN drivers/block/zram/zram_drv.c~zram-record-accessed-second drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~zram-record-accessed-second
+++ a/drivers/block/zram/zram_drv.c
@@ -107,6 +107,16 @@ static inline void zram_set_element(stru
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;
@@ -806,6 +816,8 @@ static void zram_free_page(struct zram *
{
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);
@@ -1177,6 +1189,10 @@ static int zram_bvec_rw(struct zram *zra
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);
diff -puN drivers/block/zram/zram_drv.h~zram-record-accessed-second drivers/block/zram/zram_drv.h
--- a/drivers/block/zram/zram_drv.h~zram-record-accessed-second
+++ a/drivers/block/zram/zram_drv.h
@@ -61,6 +61,7 @@ struct zram_table_entry {
unsigned long element;
};
unsigned long value;
+ u64 ac_time;
};
struct zram_stats {
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
zram-correct-flag-name-of-zram_access.patch
zram-mark-incompressible-page-as-zram_huge.patch
zram-record-accessed-second.patch
zram-introduce-zram-memory-tracking.patch
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