Messages in this thread Patch in this message | | | Subject | [PATCH 3/3] mm/vmscan: replace implicit RECLAIM_ZONE checks with explicit checks | From | Dave Hansen <> | Date | Wed, 01 Jul 2020 08:26:27 -0700 |
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From: Dave Hansen <dave.hansen@linux.intel.com>
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.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ben Widawsky <ben.widawsky@intel.com> Cc: Alex Shi <alex.shi@linux.alibaba.com> Cc: Daniel Wagner <dwagner@suse.de> Cc: "Tobin C. Harding" <tobin@kernel.org> Cc: Christoph Lameter <cl@linux.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Huang Ying <ying.huang@intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Qian Cai <cai@lca.pw> Cc: Daniel Wagner <dwagner@suse.de>
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Note: This is not cc'd to stable. It does not fix any bugs. ---
b/include/linux/swap.h | 7 +++++++ b/mm/khugepaged.c | 2 +- b/mm/page_alloc.c | 2 +- 3 files changed, 9 insertions(+), 2 deletions(-)
diff -puN include/linux/swap.h~mm-vmscan-node_reclaim_mode_helper include/linux/swap.h --- a/include/linux/swap.h~mm-vmscan-node_reclaim_mode_helper 2020-07-01 08:22:13.650955330 -0700 +++ b/include/linux/swap.h 2020-07-01 08:22:13.659955330 -0700 @@ -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; @@ -374,6 +375,12 @@ 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); diff -puN mm/khugepaged.c~mm-vmscan-node_reclaim_mode_helper mm/khugepaged.c --- a/mm/khugepaged.c~mm-vmscan-node_reclaim_mode_helper 2020-07-01 08:22:13.652955330 -0700 +++ b/mm/khugepaged.c 2020-07-01 08:22:13.660955330 -0700 @@ -709,7 +709,7 @@ 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 */ diff -puN mm/page_alloc.c~mm-vmscan-node_reclaim_mode_helper mm/page_alloc.c --- a/mm/page_alloc.c~mm-vmscan-node_reclaim_mode_helper 2020-07-01 08:22:13.655955330 -0700 +++ b/mm/page_alloc.c 2020-07-01 08:22:13.662955330 -0700 @@ -3733,7 +3733,7 @@ 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; _
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