On 11/29/22 16:17, Mel Gorman wrote:
> Explicit GFP_ATOMIC allocations get flagged ALLOC_HARDER which is a bit
> vague. In preparation for removing __GFP_ATOMIC, give GFP_ATOMIC and
> other non-blocking allocation requests equal access to reserve. Rename
> ALLOC_HARDER to ALLOC_NON_BLOCK to make it more clear what the flag
> means.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> ---
> mm/internal.h | 7 +++++--
> mm/page_alloc.c | 23 +++++++++++++----------
> 2 files changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 370500718732..98b1e526559d 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -743,7 +743,10 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
> #define ALLOC_OOM ALLOC_NO_WATERMARKS
> #endif
>
> -#define ALLOC_HARDER 0x10 /* try to alloc harder */
> +#define ALLOC_NON_BLOCK 0x10 /* Caller cannot block. Allow access
> + * to 25% of the min watermark or
> + * 62.5% if __GFP_HIGH is set.
> + */
> #define ALLOC_MIN_RESERVE 0x20 /* __GFP_HIGH set. Allow access to 50%
> * of the min watermark.
> */
> @@ -758,7 +761,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
> #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
>
> /* Flags that allow allocations below the min watermark. */
> -#define ALLOC_RESERVES (ALLOC_HARDER|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
> +#define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
>
> enum ttu_flags;
> struct tlbflush_unmap_batch;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 85a87d0ac57a..6bee987ec9a3 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3994,7 +3994,7 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
> * if it cannot get memory quickly, particularly if it's
> * also __GFP_HIGH.
> */
> - if (alloc_flags & (ALLOC_HARDER|ALLOC_HIGHATOMIC))
> + if (alloc_flags & (ALLOC_NON_BLOCK|ALLOC_HIGHATOMIC))
> min -= min / 4;
>
> /*
> @@ -4846,28 +4846,30 @@ gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order)
> * The caller may dip into page reserves a bit more if the caller
> * cannot run direct reclaim, or if the caller has realtime scheduling
> * policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
> - * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_MIN_RESERVE(__GFP_HIGH).
> + * set both ALLOC_NON_BLOCK and ALLOC_MIN_RESERVE(__GFP_HIGH).
> */
> alloc_flags |= (__force int)
> (gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
>
> - if (gfp_mask & __GFP_ATOMIC) {
> + if (!(gfp_mask & __GFP_RECLAIM)) {
This is supposed to be __GFP_DIRECT_RECLAIM right? Otherwise that includes
also __GFP_KSWAPD_RECLAIM and GFP_ATOMIC sets that one...
> /*
> * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
> * if it can't schedule.
> */
> if (!(gfp_mask & __GFP_NOMEMALLOC)) {
> - alloc_flags |= ALLOC_HARDER;
> + alloc_flags |= ALLOC_NON_BLOCK;
>
> if (order > 0)
> alloc_flags |= ALLOC_HIGHATOMIC;
> }
>
> /*
> - * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the
> - * comment for __cpuset_node_allowed().
> + * Ignore cpuset mems for non-blocking __GFP_HIGH (probably
> + * GFP_ATOMIC) rather than fail, see the comment for
> + * __cpuset_node_allowed().
> */
> - alloc_flags &= ~ALLOC_CPUSET;
> + if (alloc_flags & ALLOC_MIN_RESERVE)
> + alloc_flags &= ~ALLOC_CPUSET;
> } else if (unlikely(rt_task(current)) && in_task())
> alloc_flags |= ALLOC_MIN_RESERVE;
>
> @@ -5299,11 +5301,12 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>
> /*
> * Help non-failing allocations by giving them access to memory
> - * reserves but do not use ALLOC_NO_WATERMARKS because this
> + * reserves normally used for high priority non-blocking
> + * allocations but do not use ALLOC_NO_WATERMARKS because this
> * could deplete whole memory reserves which would just make
> - * the situation worse
> + * the situation worse.
> */
> - page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_MIN_RESERVE|ALLOC_HARDER, ac);
> + page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_MIN_RESERVE|ALLOC_NON_BLOCK, ac);
> if (page)
> goto got_pg;
>
