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SubjectRe: [RFC PATCH 10/12] mm: add the buddy system interface
On 2015/06/04 22:04, Xishi Qiu wrote:
> Add the buddy system interface for address range mirroring feature.
> Allocate mirrored pages in MIGRATE_MIRROR list. If there is no mirrored pages
> left, use other types pages.
>
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> ---
> mm/page_alloc.c | 40 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d4d2066..0fb55288 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -599,6 +599,26 @@ static inline bool is_mirror_pfn(unsigned long pfn)
>
> return false;
> }
> +
> +static inline bool change_to_mirror(gfp_t gfp_flags, int high_zoneidx)
> +{
> + /*
> + * Do not alloc mirrored memory below 4G, because 0-4G is
> + * all mirrored by default, and the list is always empty.
> + */
> + if (high_zoneidx < ZONE_NORMAL)
> + return false;
> +
> + /* Alloc mirrored memory for only kernel */
> + if (gfp_flags & __GFP_MIRROR)
> + return true;

GFP_KERNEL itself should imply mirror, I think.

> +
> + /* Alloc mirrored memory for both user and kernel */
> + if (sysctl_mirrorable)
> + return true;

Reading this, I think this sysctl is not good. The user cannot know what is mirrored
because memory may not be mirrored until the sysctl is set.

Thanks,
-Kame


> +
> + return false;
> +}
> #endif
>
> /*
> @@ -1796,7 +1816,10 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
> WARN_ON_ONCE(order > 1);
> }
> spin_lock_irqsave(&zone->lock, flags);
> - page = __rmqueue(zone, order, migratetype);
> + if (is_migrate_mirror(migratetype))
> + page = __rmqueue_smallest(zone, order, migratetype);
> + else
> + page = __rmqueue(zone, order, migratetype);
> spin_unlock(&zone->lock);
> if (!page)
> goto failed;
> @@ -2928,6 +2951,11 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
> if (IS_ENABLED(CONFIG_CMA) && ac.migratetype == MIGRATE_MOVABLE)
> alloc_flags |= ALLOC_CMA;
>
> +#ifdef CONFIG_MEMORY_MIRROR
> + if (change_to_mirror(gfp_mask, ac.high_zoneidx))
> + ac.migratetype = MIGRATE_MIRROR;
> +#endif
> +
> retry_cpuset:
> cpuset_mems_cookie = read_mems_allowed_begin();
>
> @@ -2943,9 +2971,19 @@ retry_cpuset:
>
> /* First allocation attempt */
> alloc_mask = gfp_mask|__GFP_HARDWALL;
> +retry:
> page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);
> if (unlikely(!page)) {
> /*
> + * If there is no mirrored memory, we will alloc other
> + * types memory.
> + */
> + if (is_migrate_mirror(ac.migratetype)) {
> + ac.migratetype = gfpflags_to_migratetype(gfp_mask);
> + goto retry;
> + }
> +
> + /*
> * Runtime PM, block IO and its error handling path
> * can deadlock because I/O on the device might not
> * complete.
>




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