The patch titled
Subject: mm/vmscan: replace implicit RECLAIM_ZONE checks with explicit checks
has been added to the -mm tree. Its filename is
mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Subject: mm/vmscan: replace implicit RECLAIM_ZONE checks with explicit checks
RECLAIM_ZONE was assumed to be unused because it was never explicitly used
in the kernel. However, there were a number of places where it was
checked implicitly by checking 'node_reclaim_mode' for a zero value.
These zero checks are not great because it is not obvious what a zero mode
*means* in the code. Replace them with a helper which makes it more
obvious: node_reclaim_enabled().
This helper also provides a handy place to explicitly check the
RECLAIM_ZONE bit itself. Check it explicitly there to make it more
obvious where the bit can affect behavior.
This should have no functional impact.
Link: https://lkml.kernel.org/r/20210219172559.BF589C44@xxxxxxxxxxxxxxxxxx
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: "Tobin C. Harding" <tobin@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Cc: Daniel Wagner <dwagner@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 7 +++++++
mm/khugepaged.c | 2 +-
mm/page_alloc.c | 2 +-
3 files changed, 9 insertions(+), 2 deletions(-)
--- a/include/linux/swap.h~mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks
+++ a/include/linux/swap.h
@@ -12,6 +12,7 @@
#include <linux/fs.h>
#include <linux/atomic.h>
#include <linux/page-flags.h>
+#include <uapi/linux/mempolicy.h>
#include <asm/page.h>
struct notifier_block;
@@ -378,6 +379,12 @@ extern int sysctl_min_slab_ratio;
#define node_reclaim_mode 0
#endif
+static inline bool node_reclaim_enabled(void)
+{
+ /* Is any node_reclaim_mode bit set? */
+ return node_reclaim_mode & (RECLAIM_ZONE|RECLAIM_WRITE|RECLAIM_UNMAP);
+}
+
extern void check_move_unevictable_pages(struct pagevec *pvec);
extern int kswapd_run(int nid);
--- a/mm/khugepaged.c~mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks
+++ a/mm/khugepaged.c
@@ -809,7 +809,7 @@ static bool khugepaged_scan_abort(int ni
* If node_reclaim_mode is disabled, then no extra effort is made to
* allocate memory locally.
*/
- if (!node_reclaim_mode)
+ if (!node_reclaim_enabled())
return false;
/* If there is a count for this node already, it must be acceptable */
--- a/mm/page_alloc.c~mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks
+++ a/mm/page_alloc.c
@@ -3922,7 +3922,7 @@ retry:
if (alloc_flags & ALLOC_NO_WATERMARKS)
goto try_this_zone;
- if (node_reclaim_mode == 0 ||
+ if (!node_reclaim_enabled() ||
!zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
continue;
_
Patches currently in -mm which might be from dave.hansen@xxxxxxxxxxxxxxx are
mm-vmscan-move-reclaim-bits-to-uapi-header.patch
mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks.patch
