mm/page_io.c: annotate refault stalls from swap_readpage (93779069) · Commits · 戴 / test

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>

mm/page_io.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

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