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mm/page_io.c: annotate refault stalls from swap_readpage

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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@linux-foundation.org: add comment, per Johannes]
Link: http://lkml.kernel.org/r/20191010152134.38545-1-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2019-11-30 17:58:29 -08:00 committed by Linus Torvalds
parent dd33d29a19
commit 937790699b
1 changed files with 13 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

15
mm/page_io.c
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@ -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, bool synchronous)
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, bool synchronous)
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, bool synchronous)
}
count_vm_event(PSWPIN);
return 0;
goto out;
}
ret = 0;
@ -418,6 +428,7 @@ int swap_readpage(struct page *page, bool synchronous)
bio_put(bio);
out:
psi_memstall_leave(&pflags);
return ret;
}