On Wed, 1 Jul 2020, Dave Hansen wrote:
> 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);
If a user writes a bit that isn't a RECLAIM_* bit to vm.zone_reclaim_mode
today, it acts as though RECLAIM_ZONE is enabled: we try to reclaim in
zonelist order before falling back to the next zone in the page allocator.
The sysctl doesn't enforce any max value :/ I dont know if there is any
such user, but this would break them if there is.
Should this simply be return !!node_reclaim_mode?
