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Date:   Mon, 22 Mar 2021 15:46:25 +0100
From:   Michal Hocko <mhocko@suse.com>
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Shakeel Butt <shakeelb@google.com>,
        Oscar Salvador <osalvador@suse.de>,
        David Hildenbrand <david@redhat.com>,
        Muchun Song <songmuchun@bytedance.com>,
        David Rientjes <rientjes@google.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
        Mina Almasry <almasrymina@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 7/8] hugetlb: add update_and_free_page_no_sleep for
 irq context
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On Mon 22-03-21 15:42:27, Michal Hocko wrote:
[...]
> Besides that the changelog doesn't really say anything about changed
> user visible behavior change. Now if somebody decreases the GB huge pool
> from the userspace the real effect on the freed up memory will be
> postponed to some later time. That "later" is unpredictable as it
> depends on WQ utilization. We definitely need some sort of
> wait_for_inflight pages. One way to do that would be to have a dedicated
> WQ and schedule a sync work item after the pool has been shrunk and wait
> for that item.

Scratch that. It is not really clear from the patch context but after
looking at the resulting code set_max_huge_pages will use the blockable
update_and_free_page so we should be fine.

Sorry about the noise!
-- 
Michal Hocko
SUSE Labs