From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7910C2D0A3 for ; Thu, 22 Oct 2020 01:55:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B4ADB21D43 for ; Thu, 22 Oct 2020 01:55:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B4ADB21D43 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hisilicon.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B74EF6B005D; Wed, 21 Oct 2020 21:55:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AFEC96B0062; Wed, 21 Oct 2020 21:55:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9ECC96B0068; Wed, 21 Oct 2020 21:55:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0052.hostedemail.com [216.40.44.52]) by kanga.kvack.org (Postfix) with ESMTP id 6D4C06B005D for ; Wed, 21 Oct 2020 21:55:00 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id EA7FB2476 for ; Thu, 22 Oct 2020 01:54:59 +0000 (UTC) X-FDA: 77397893118.23.robin77_42129ad2724d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin23.hostedemail.com (Postfix) with ESMTP id C80BB37604 for ; Thu, 22 Oct 2020 01:54:59 +0000 (UTC) X-HE-Tag: robin77_42129ad2724d X-Filterd-Recvd-Size: 2919 Received: from huawei.com (szxga04-in.huawei.com [45.249.212.190]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Thu, 22 Oct 2020 01:54:59 +0000 (UTC) Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 0D637F6DA850343BA93E; Thu, 22 Oct 2020 09:54:56 +0800 (CST) Received: from [127.0.0.1] (10.143.60.252) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.487.0; Thu, 22 Oct 2020 09:54:54 +0800 Subject: Re: [PATCH rfc 0/2] mm: cma: make cma_release() non-blocking To: Roman Gushchin , Andrew Morton CC: Zi Yan , Joonsoo Kim , "Mike Kravetz" , , , References: <20201016225254.3853109-1-guro@fb.com> From: "Xiaqing (A)" Message-ID: Date: Thu, 22 Oct 2020 09:54:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20201016225254.3853109-1-guro@fb.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.143.60.252] X-CFilter-Loop: Reflected X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020/10/17 6:52, Roman Gushchin wrote: > This small patchset makes cma_release() non-blocking and simplifies > the code in hugetlbfs, where previously we had to temporarily drop > hugetlb_lock around the cma_release() call. > > It should help Zi Yan on his work on 1 GB THPs: splitting a gigantic > THP under a memory pressure requires a cma_release() call. If it's > a blocking function, it complicates the already complicated code. > Because there are at least two use cases like this (hugetlbfs is > another example), I believe it's just better to make cma_release() > non-blocking. > > It also makes it more consistent with other memory releasing functions > in the kernel: most of them are non-blocking. > > > Roman Gushchin (2): > mm: cma: make cma_release() non-blocking > mm: hugetlb: don't drop hugetlb_lock around cma_release() call > > mm/cma.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++-- > mm/hugetlb.c | 6 ------ > 2 files changed, 49 insertions(+), 8 deletions(-) > I don't think this patch is a good idea.It transfers part or even all of the time of cma_release to cma_alloc, which is more concerned by performance indicators. On Android phones, CPU resource competition is intense in many scenarios, As a result, kernel threads and workers can be scheduled only after some ticks or more. In this case, the performance of cma_alloc will deteriorate significantly, which is not good news for many services on Android.