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Message-ID: <e64d8888-f00c-d360-b35c-54396c6fff2d@huaweicloud.com>
Date: Mon, 10 Apr 2023 17:03:31 +0800
From: Wu Bo <wubo@...weicloud.com>
To: "zhaoyang.huang" <zhaoyang.huang@...soc.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Minchan Kim <minchan@...nel.org>,
Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Zhaoyang Huang <huangzhaoyang@...il.com>, ke.wang@...soc.com
Subject: Re: [RFC PATCHv2] mm: introduce defer free for cma
On 2023/4/10 16:46, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
>
> Continues page blocks are expensive for the system. Introducing defer free
> mechanism to buffer some which make the allocation easier. The shrinker will
> ensure the page block can be reclaimed when there is memory pressure.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> ---
> v2: fix build warning and regist shrinker
> ---
> ---
> mm/cma.c | 151 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> mm/cma.h | 11 +++++
> 2 files changed, 160 insertions(+), 2 deletions(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index 4a978e0..6d2fd24 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -39,6 +39,10 @@
> unsigned cma_area_count;
> static DEFINE_MUTEX(cma_mutex);
>
> +static unsigned long cma_defer_free_count(struct shrinker *shrinker,
> + struct shrink_control *sc);
> +static unsigned long cma_defer_free_scan(struct shrinker *shrinker,
> + struct shrink_control *sc);
> phys_addr_t cma_get_base(const struct cma *cma)
> {
> return PFN_PHYS(cma->base_pfn);
> @@ -153,6 +157,20 @@ static int __init cma_init_reserved_areas(void)
> }
> core_initcall(cma_init_reserved_areas);
>
> +static unsigned long cma_free_get(struct cma *cma)
> +{
> + unsigned long used;
> + unsigned long val;
> +
> + spin_lock_irq(&cma->lock);
> + /* pages counter is smaller than sizeof(int) */
> + used = bitmap_weight(cma->bitmap, (int)cma_bitmap_maxno(cma));
> + val = cma->count - ((u64)used << cma->order_per_bit);
> + spin_unlock_irq(&cma->lock);
> +
> + return val;
> +}
> +
> void __init cma_reserve_pages_on_error(struct cma *cma)
> {
> cma->reserve_pages_on_error = true;
> @@ -212,6 +230,13 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
> cma_area_count++;
> totalcma_pages += (size / PAGE_SIZE);
>
> + cma->batch = cma->count >> 1;
> + cma->shrinker.count_objects = cma_defer_free_count;
> + cma->shrinker.scan_objects = cma_defer_free_scan;
> + cma->shrinker.seeks = DEFAULT_SEEKS;
> + cma->shrinker.batch = 0;
> +
> + register_shrinker(&cma->shrinker, "cma-shrinker");
> return 0;
> }
>
> @@ -411,6 +436,46 @@ static void cma_debug_show_areas(struct cma *cma)
> static inline void cma_debug_show_areas(struct cma *cma) { }
> #endif
>
> +static int cma_defer_area_fetch(struct cma *cma, unsigned long pfn,
> + unsigned long count)
> +{
> + struct cma_defer_free_area *area;
> + unsigned long new_pfn;
> + int ret = -1;
> +
> + if (!atomic64_read(&cma->defer_count))
> + return ret;
> + if (count <= atomic64_read(&cma->defer_count)) {
> + spin_lock_irq(&cma->lock);
> + list_for_each_entry(area, &cma->defer_free, list) {
> + /*area found for given pfn and count*/
> + if (pfn >= area->pfn && count <= area->count) {
> + list_del(&area->list);
> + /*set bits for allocated pfn*/
> + bitmap_set(cma->bitmap, pfn - cma->base_pfn, count);
> + kfree(area);
> + atomic64_sub(count, &cma->defer_count);
> + /*release the rest pfn to cma*/
> + if (!list_empty(&cma->defer_free) && (pfn == area->pfn)) {
There is a null pointer reference here?
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