Re: [PATCH v2 3/3] mm/shuffle: remove dynamic reconfiguration

Michal Hocko
2020-06-22T15:37:28Z

On Fri 19-06-20 14:59:22, David Hildenbrand wrote:
> Commit e900a918b098 ("mm: shuffle initial free memory to improve
> memory-side-cache utilization") promised "autodetection of a
> memory-side-cache (to be added in a follow-on patch)" over a year ago.
>
> The original series included patches [1], however, they were dropped
> during review [2] to be followed-up later.
>
> Due to lack of platforms that publish an HMAT, autodetection is currently
> not implemented. However, manual activation is actively used [3]. Let's
> simplify for now and re-add when really (ever?) needed.
>
> [1] https://lkml.kernel.org/r/154510700291.1941238.817190985966612531.stgit@dwillia2-desk3.amr.corp.intel.com
> [2] https://lkml.kernel.org/r/154690326478.676627.103843791978176914.stgit@dwillia2-desk3.amr.corp.intel.com
> [3] https://lkml.kernel.org/r/CAPcyv4irwGUU2x+c6b4L=KbB1dnasNKaaZd6oSpYjL9kfsnROQ@mail.gmail.com
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Huang Ying <ying.huang@intel.com>
> Cc: Wei Yang <richard.weiyang@gmail.com>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/shuffle.c | 28 ++--------------------------
> mm/shuffle.h | 17 -----------------
> 2 files changed, 2 insertions(+), 43 deletions(-)
>
> diff --git a/mm/shuffle.c b/mm/shuffle.c
> index dd13ab851b3ee..9b5cd4b004b0f 100644
> --- a/mm/shuffle.c
> +++ b/mm/shuffle.c
> @@ -10,33 +10,11 @@
> #include "shuffle.h"
>
> DEFINE_STATIC_KEY_FALSE(page_alloc_shuffle_key);
> -static unsigned long shuffle_state __ro_after_init;
> -
> -/*
> - * Depending on the architecture, module parameter parsing may run
> - * before, or after the cache detection. SHUFFLE_FORCE_DISABLE prevents,
> - * or reverts the enabling of the shuffle implementation. SHUFFLE_ENABLE
> - * attempts to turn on the implementation, but aborts if it finds
> - * SHUFFLE_FORCE_DISABLE already set.
> - */
> -__meminit void page_alloc_shuffle(enum mm_shuffle_ctl ctl)
> -{
> - if (ctl == SHUFFLE_FORCE_DISABLE)
> - set_bit(SHUFFLE_FORCE_DISABLE, &shuffle_state);
> -
> - if (test_bit(SHUFFLE_FORCE_DISABLE, &shuffle_state)) {
> - if (test_and_clear_bit(SHUFFLE_ENABLE, &shuffle_state))
> - static_branch_disable(&page_alloc_shuffle_key);
> - } else if (ctl == SHUFFLE_ENABLE
> - && !test_and_set_bit(SHUFFLE_ENABLE, &shuffle_state))
> - static_branch_enable(&page_alloc_shuffle_key);
> -}
>
> static bool shuffle_param;
> static int shuffle_show(char *buffer, const struct kernel_param *kp)
> {
> - return sprintf(buffer, "%c\n", test_bit(SHUFFLE_ENABLE, &shuffle_state)
> - ? 'Y' : 'N');
> + return sprintf(buffer, "%c\n", shuffle_param ? 'Y' : 'N');
> }
>
> static __meminit int shuffle_store(const char *val,
> @@ -47,9 +25,7 @@ static __meminit int shuffle_store(const char *val,
> if (rc < 0)
> return rc;
> if (shuffle_param)
> - page_alloc_shuffle(SHUFFLE_ENABLE);
> - else
> - page_alloc_shuffle(SHUFFLE_FORCE_DISABLE);
> + static_branch_enable(&page_alloc_shuffle_key);
> return 0;
> }
> module_param_call(shuffle, shuffle_store, shuffle_show, &shuffle_param, 0400);
> diff --git a/mm/shuffle.h b/mm/shuffle.h
> index 4d79f03b6658f..71b784f0b7c3e 100644
> --- a/mm/shuffle.h
> +++ b/mm/shuffle.h
> @@ -4,23 +4,10 @@
> #define _MM_SHUFFLE_H
> #include <linux/jump_label.h>
>
> -/*
> - * SHUFFLE_ENABLE is called from the command line enabling path, or by
> - * platform-firmware enabling that indicates the presence of a
> - * direct-mapped memory-side-cache. SHUFFLE_FORCE_DISABLE is called from
> - * the command line path and overrides any previous or future
> - * SHUFFLE_ENABLE.
> - */
> -enum mm_shuffle_ctl {
> - SHUFFLE_ENABLE,
> - SHUFFLE_FORCE_DISABLE,
> -};
> -
> #define SHUFFLE_ORDER (MAX_ORDER-1)
>
> #ifdef CONFIG_SHUFFLE_PAGE_ALLOCATOR
> DECLARE_STATIC_KEY_FALSE(page_alloc_shuffle_key);
> -extern void page_alloc_shuffle(enum mm_shuffle_ctl ctl);
> extern void __shuffle_free_memory(pg_data_t *pgdat);
> extern bool shuffle_pick_tail(void);
> static inline void shuffle_free_memory(pg_data_t *pgdat)
> @@ -58,10 +45,6 @@ static inline void shuffle_zone(struct zone *z)
> {
> }
>
> -static inline void page_alloc_shuffle(enum mm_shuffle_ctl ctl)
> -{
> -}
> -
> static inline bool is_shuffle_order(int order)
> {
> return false;
> --
> 2.26.2

--
Michal Hocko
SUSE Labs