Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Subject: Re: [PATCH v2] mm/huge_memory: prevent THP_ZERO_PAGE_ALLOC increased
 twice
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
References: <20220908035533.2186159-1-liushixin2@huawei.com>
 <20220908123102.rpihrmisv55j3b2o@box.shutemov.name>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>,
        Kefeng Wang <wangkefeng.wang@huawei.com>
From:   Liu Shixin <liushixin2@huawei.com>
Message-ID: <84a82033-ceb5-d8a2-3bae-a31574a5ff28@huawei.com>
Date:   Thu, 8 Sep 2022 21:07:04 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101
 Thunderbird/45.7.1
MIME-Version: 1.0
In-Reply-To: <20220908123102.rpihrmisv55j3b2o@box.shutemov.name>
Content-Type: text/plain; charset="windows-1252"
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 2022/9/8 20:31, Kirill A. Shutemov wrote:
> On Thu, Sep 08, 2022 at 11:55:33AM +0800, Liu Shixin wrote:
>> If two or more threads call get_huge_zero_page concurrently,
>> THP_ZERO_PAGE_ALLOC may increased two or more times. But actually,
>> this should only count as once since the extra zero pages has been
>> freed. Redefine its meaning to indicate the times a huge zero page
>> used for thp is successfully allocated.
> I don't particularly care, but it is not obvoius why the new behaviour is
> better.
The user who read the value may be more concerned about the huge zero pages that are
really allocated using for thp and can indicated the times of calling huge_zero_page_shrinker.
I misunderstood when I first saw it.
>
> All huge zero pages are freed apart from possibly the last one allocated.
>