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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6E7EC433EF for ; Tue, 10 May 2022 02:10:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E9F686B0072; Mon, 9 May 2022 22:10:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E26AA6B0073; Mon, 9 May 2022 22:10:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CC8396B0074; Mon, 9 May 2022 22:10:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id B61C36B0072 for ; Mon, 9 May 2022 22:10:53 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 71B7030753 for ; Tue, 10 May 2022 02:10:53 +0000 (UTC) X-FDA: 79448205186.10.C680B08 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf28.hostedemail.com (Postfix) with ESMTP id C53A5C008C for ; Tue, 10 May 2022 02:10:33 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Ky1h2208nz1JBmt; Tue, 10 May 2022 10:09:38 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 10 May 2022 10:10:48 +0800 Subject: Re: [PATCH 10/15] mm/swap: break the loop if matching device is found To: Andrew Morton CC: , , , , , , , , , , References: <20220509131416.17553-1-linmiaohe@huawei.com> <20220509131416.17553-11-linmiaohe@huawei.com> <20220509141602.b6be120b80d0ab3218fe619a@linux-foundation.org> From: Miaohe Lin Message-ID: Date: Tue, 10 May 2022 10:10:47 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220509141602.b6be120b80d0ab3218fe619a@linux-foundation.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Authentication-Results: imf28.hostedemail.com; dkim=none; spf=pass (imf28.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C53A5C008C X-Stat-Signature: 9qwi5ybroxn75kekxz3rdyitizigpjqj X-HE-Tag: 1652148633-842271 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 2022/5/10 5:16, Andrew Morton wrote: > On Mon, 9 May 2022 21:14:11 +0800 Miaohe Lin wrote: > >> We can break the loop if matching device is found to save some possible >> cpu cycles because there should be only one matching device and there is >> no need to continue if the matching one is already found. >> >> ... >> >> --- a/mm/swapfile.c >> +++ b/mm/swapfile.c >> @@ -1692,6 +1692,8 @@ int swap_type_of(dev_t device, sector_t offset) >> spin_unlock(&swap_lock); >> return type; >> } >> + >> + break; >> } >> } >> spin_unlock(&swap_lock); > > Are you sure? If we have two S_ISREG swapfiles on the same device, > don't they have the same sis->bdev? Oh, I missed this use case. Sorry about it! :( > > If not, why bother passing `offset' into this function at all? Yes, you're right. 'offset' indicates the swap header location. Will drop this patch. Thanks! > . >