@@ -389,6 +389,9 @@ extern void end_swap_bio_write(struct bio *bio);
extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
bio_end_io_t end_write_func);
extern int swap_set_page_dirty(struct page *page);
+#ifdef CONFIG_ZSWAP_IO_SWITCH
+extern void swap_io_in_flight(struct page *page, unsigned int inflight[2]);
+#endif
int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
unsigned long nr_pages, sector_t start_block);
@@ -546,6 +546,24 @@ config ZSWAP
they have not be fully explored on the large set of potential
configurations and workloads that exist.
+config ZSWAP_IO_SWITCH
+ bool "Compressed cache for swap pages according to the IO status"
+ depends on ZSWAP
+ def_bool n
+ help
+ This function help the system that normal swap speed is higher
+ than zswap speed to handle the swap IO issue.
+ For example, a VM that is disk device is not set cache config or
+ set cache=writeback.
+
+ This function make zswap just work when the disk of the swap file
+ is under high IO load.
+ It add two parameters read_in_flight_limit and write_in_flight_limit to
+ zswap. When zswap is enabled, pages will be stored to zswap only
+ when the IO in flight number of swap device is bigger than
+ zswap_read_in_flight_limit or zswap_write_in_flight_limit.
+ If unsure, say "n".
+
config ZPOOL
tristate "Common API for compressed memory storage"
help
@@ -434,3 +434,19 @@ int swap_set_page_dirty(struct page *page)
return __set_page_dirty_no_writeback(page);
}
}
+
+#ifdef CONFIG_ZSWAP_IO_SWITCH
+void swap_io_in_flight(struct page *page, unsigned int inflight[2])
+{
+ struct swap_info_struct *sis = page_swap_info(page);
+
+ if (!sis->bdev) {
+ inflight[0] = 0;
+ inflight[1] = 0;
+ return;
+ }
+
+ part_in_flight_rw(bdev_get_queue(sis->bdev), sis->bdev->bd_part,
+ inflight);
+}
+#endif
@@ -62,6 +62,13 @@ static u64 zswap_reject_compress_poor;
static u64 zswap_reject_alloc_fail;
/* Store failed because the entry metadata could not be allocated (rare) */
static u64 zswap_reject_kmemcache_fail;
+#ifdef CONFIG_ZSWAP_IO_SWITCH
+/* Store failed because zswap_read_in_flight_limit or
+ * zswap_write_in_flight_limit is bigger than IO in flight number of
+ * swap device
+ */
+static u64 zswap_reject_io;
+#endif
/* Duplicate store was encountered (rare) */
static u64 zswap_duplicate_entry;
@@ -114,6 +121,22 @@ static bool zswap_same_filled_pages_enabled = true;
module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
bool, 0644);
+#ifdef CONFIG_ZSWAP_IO_SWITCH
+/* zswap will not try to store the page if zswap_read_in_flight_limit is
+ * bigger than IO read in flight number of swap device
+ */
+static unsigned int zswap_read_in_flight_limit;
+module_param_named(read_in_flight_limit, zswap_read_in_flight_limit,
+ uint, 0644);
+
+/* zswap will not try to store the page if zswap_write_in_flight_limit is
+ * bigger than IO write in flight number of swap device
+ */
+static unsigned int zswap_write_in_flight_limit;
+module_param_named(write_in_flight_limit, zswap_write_in_flight_limit,
+ uint, 0644);
+#endif
+
/*********************************
* data structures
**********************************/
@@ -1009,6 +1032,34 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
goto reject;
}
+#ifdef CONFIG_ZSWAP_IO_SWITCH
+ if (zswap_read_in_flight_limit || zswap_write_in_flight_limit) {
+ unsigned int inflight[2];
+ bool should_swap = false;
+
+ swap_io_in_flight(page, inflight);
+
+ if (zswap_write_in_flight_limit &&
+ inflight[1] < zswap_write_in_flight_limit)
+ should_swap = true;
+
+ if (zswap_read_in_flight_limit &&
+ (should_swap ||
+ (!should_swap && !zswap_write_in_flight_limit))) {
+ if (inflight[0] < zswap_read_in_flight_limit)
+ should_swap = true;
+ else
+ should_swap = false;
+ }
+
+ if (should_swap) {
+ zswap_reject_io++;
+ ret = -EIO;
+ goto reject;
+ }
+ }
+#endif
+
/* reclaim space if needed */
if (zswap_is_full()) {
zswap_pool_limit_hit++;
@@ -1264,6 +1315,10 @@ static int __init zswap_debugfs_init(void)
zswap_debugfs_root, &zswap_reject_kmemcache_fail);
debugfs_create_u64("reject_compress_poor", 0444,
zswap_debugfs_root, &zswap_reject_compress_poor);
+#ifdef CONFIG_ZSWAP_IO_SWITCH
+ debugfs_create_u64("reject_io", 0444,
+ zswap_debugfs_root, &zswap_reject_io);
+#endif
debugfs_create_u64("written_back_pages", 0444,
zswap_debugfs_root, &zswap_written_back_pages);
debugfs_create_u64("duplicate_entry", 0444,
This is the second version of this patch. The previous version is in https://lkml.org/lkml/2019/9/11/935 I updated the commit introduction and Kconfig because it is not clear. Currently, I use a VM that has 2 CPUs, 4G memory and 4G swap file. I found that swap will affect the IO performance when it is running. So I open zswap to handle it because it just use CPU cycles but not disk IO. It work OK but I found that zswap is slower than normal swap in this VM. zswap is about 300M/s and normal swap is about 500M/s. (The reason is disk inside VM has fscache in host machine.) So open zswap is make memory shrinker slower but good for IO performance in this VM. So I just want zswap work when the disk of the swap file is under high IO load. This commit is designed for this idea. It add two parameters read_in_flight_limit and write_in_flight_limit to zswap. In zswap_frontswap_store, pages will be stored to zswap only when the IO in flight number of swap device is bigger than zswap_read_in_flight_limit or zswap_write_in_flight_limit when zswap is enabled. Then the zswap just work when the IO in flight number of swap device is low. Signed-off-by: Hui Zhu <teawaterz@linux.alibaba.com> --- include/linux/swap.h | 3 +++ mm/Kconfig | 18 +++++++++++++++++ mm/page_io.c | 16 +++++++++++++++ mm/zswap.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 92 insertions(+)