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Date:   Tue, 6 Apr 2021 11:17:48 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>,
        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>,
        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>,
        Hillf Danton <hdanton@sina.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Barry Song <song.bao.hua@hisilicon.com>,
        Will Deacon <will@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v4 1/8] mm/cma: change cma mutex to irq safe spinlock
Message-ID: <YGwnPCPaq1xKh/88@hirez.programming.kicks-ass.net>
References: <20210405230043.182734-1-mike.kravetz@oracle.com>
 <20210405230043.182734-2-mike.kravetz@oracle.com>
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On Mon, Apr 05, 2021 at 04:00:36PM -0700, Mike Kravetz wrote:
> The lock doesn't protect any sleepable operation so it can be changed to
> a (irq aware) spin lock. The bitmap processing should be quite fast in
> typical case but if cma sizes grow to TB then we will likely need to
> replace the lock by a more optimized bitmap implementation.

Or an rb-tree that stores ranges, which should also be much cheaper
storage wise, for those sizes.