The patch titled
Subject: mm/page_io.c: annotate refault stalls from swap_readpage
has been removed from the -mm tree. Its filename was
mm-annotate-refault-stalls-from-swap_readpage.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: mm/page_io.c: annotate refault stalls from swap_readpage
If a block device supports rw_page operation, it doesn't submit bios so
the annotation in submit_bio() for refault stall doesn't work. It happens
with zram in android, especially swap read path which could consume CPU
cycle for decompress. It is also a problem for zswap which uses
frontswap.
Annotate swap_readpage() to account the synchronous IO overhead to prevent
underreport memory pressure.
[akpm@xxxxxxxxxxxxxxxxxxxx: add comment, per Johannes]
Link: http://lkml.kernel.org/r/20191010152134.38545-1-minchan@xxxxxxxxxx
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_io.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
--- a/mm/page_io.c~mm-annotate-refault-stalls-from-swap_readpage
+++ a/mm/page_io.c
@@ -22,6 +22,7 @@
#include <linux/writeback.h>
#include <linux/frontswap.h>
#include <linux/blkdev.h>
+#include <linux/psi.h>
#include <linux/uio.h>
#include <linux/sched/task.h>
#include <asm/pgtable.h>
@@ -354,10 +355,19 @@ int swap_readpage(struct page *page, boo
struct swap_info_struct *sis = page_swap_info(page);
blk_qc_t qc;
struct gendisk *disk;
+ unsigned long pflags;
VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageUptodate(page), page);
+
+ /*
+ * Count submission time as memory stall. When the device is congested,
+ * or the submitting cgroup IO-throttled, submission can be a
+ * significant part of overall IO time.
+ */
+ psi_memstall_enter(&pflags);
+
if (frontswap_load(page) == 0) {
SetPageUptodate(page);
unlock_page(page);
@@ -371,7 +381,7 @@ int swap_readpage(struct page *page, boo
ret = mapping->a_ops->readpage(swap_file, page);
if (!ret)
count_vm_event(PSWPIN);
- return ret;
+ goto out;
}
ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
@@ -382,7 +392,7 @@ int swap_readpage(struct page *page, boo
}
count_vm_event(PSWPIN);
- return 0;
+ goto out;
}
ret = 0;
@@ -418,6 +428,7 @@ int swap_readpage(struct page *page, boo
bio_put(bio);
out:
+ psi_memstall_leave(&pflags);
return ret;
}
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
