linux-kernel - Re: [PATCH 1/8] mm: cma: introduce cma_release

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Date:   Thu, 25 Mar 2021 11:13:53 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        David Rientjes <rientjes@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Waiman Long <longman@...hat.com>, Peter Xu <peterx@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Hillf Danton <hdanton@...a.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/8] mm: cma: introduce cma_release_nowait()

On 25.03.21 11:11, Michal Hocko wrote:
> On Thu 25-03-21 10:45:19, Michal Hocko wrote:
>> On Wed 24-03-21 17:28:28, Mike Kravetz wrote:
>> [...]
>>>   phys_addr_t cma_get_base(const struct cma *cma)
>>>   {
>>>   	return PFN_PHYS(cma->base_pfn);
>>> @@ -146,6 +155,10 @@ static int __init cma_init_reserved_areas(void)
>>>   	for (i = 0; i < cma_area_count; i++)
>>>   		cma_activate_area(&cma_areas[i]);
>>>   
>>> +	cma_release_wq = create_workqueue("cma_release");
>>
>> Considering the workqueue is used to free up memory it should likely be
>> WQ_MEM_RECLAIM to prevent from long stalls when WQs are overloaded.
>>
>> I cannot judge the CMA parts from a very quick glance this looks
>> reasonably.
> 
> I have overlooked that
> +static void cma_clear_bitmap_fn(struct work_struct *work)
> +{
> +       struct cma_clear_bitmap_work *w;
> +
> +       w = container_of(work, struct cma_clear_bitmap_work, work);
> +
> +       cma_clear_bitmap(w->cma, w->pfn, w->count);
> +
> +       __free_page(pfn_to_page(w->pfn));
> +}
> 
> should be doing free_contig_range with w->count target.
> 

Then the name "cma_clear_bitmap_fn" is misleading.

-- 
Thanks,

David / dhildenb