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 E5286C5479D for ; Wed, 11 Jan 2023 23:53:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 273568E0002; Wed, 11 Jan 2023 18:53:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1FC518E0001; Wed, 11 Jan 2023 18:53:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 09DFB8E0002; Wed, 11 Jan 2023 18:53:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id EABAA8E0001 for ; Wed, 11 Jan 2023 18:53:46 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id C56C0A0639 for ; Wed, 11 Jan 2023 23:53:46 +0000 (UTC) X-FDA: 80344173252.08.08C931F Received: from r3-17.sinamail.sina.com.cn (r3-17.sinamail.sina.com.cn [202.108.3.17]) by imf25.hostedemail.com (Postfix) with ESMTP id 7420AA0009 for ; Wed, 11 Jan 2023 23:53:42 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=none; spf=pass (imf25.hostedemail.com: domain of hdanton@sina.com designates 202.108.3.17 as permitted sender) smtp.mailfrom=hdanton@sina.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1673481225; a=rsa-sha256; cv=none; b=CdiFR1dtoT5b1LpmHQEgYk8ccD4zwQYwNZAX7fKy6Re731YWNhU6GEwq1I1hoXGn1RfqQ1 wBA2H0B1dORsvC7M1ZeEp/wJ2GyFH8QwMjwFlp+4g2w3i6Dyt4jD8EVwdkWx1qMAvVnna9 mbA43yS0AZdyevXGebcc4wnR7butSZU= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=none; spf=pass (imf25.hostedemail.com: domain of hdanton@sina.com designates 202.108.3.17 as permitted sender) smtp.mailfrom=hdanton@sina.com; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1673481225; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=uTw/wMlrO6fK0ZZCo9rjdGbrXUZ1sLBlNhVOl2Rhr3M=; b=5OPqCenGT1Y7FUF+YI+oBvQbttENjTe9jkchpvBUmxhDAn9H26AEnw+0z8CnmcaLKVDVGE vJ+x8k93wVQW21GAp4nI5BhRczvsPZYBOYxXTxzaVR7moAcGbgGU+Njjq/Ji/NtNWKwLpq zGDoh/+4hZ7oGGW2HiVr9ofWwZHFtew= Received: from unknown (HELO localhost.localdomain)([114.249.61.130]) by sina.com (172.16.97.27) with ESMTP id 63BF4B9A0000DDB7; Wed, 12 Jan 2023 07:51:56 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 41050449285735 From: Hillf Danton To: Nhat Pham Cc: hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bfoster@redhat.com, willy@infradead.org Subject: Re: [PATCH v5 2/3] cachestat: implement cachestat syscall Date: Thu, 12 Jan 2023 07:53:25 +0800 Message-Id: <20230111235325.447-1-hdanton@sina.com> In-Reply-To: <20230104231127.2634648-3-nphamcs@gmail.com> References: <20230104231127.2634648-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 7420AA0009 X-Rspamd-Server: rspam01 X-Stat-Signature: dwgfoxkggoiztc9dzp4dt8chk6wx3ywi X-HE-Tag: 1673481222-741610 X-HE-Meta: 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 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 4 Jan 2023 15:11:26 -0800 Nhat Pham > Implement a new syscall that queries cache state of a file and > summarizes the number of cached pages, number of dirty pages, number of > pages marked for writeback, number of (recently) evicted pages, etc. in > a given range. Feel free to add why. Do copy-and-paste if it is in the cover letter. > > +/** > + * filemap_cachestat() - compute the page cache statistics of a mapping > + * @mapping: The mapping to compute the statistics for. > + * @first_index: The starting page cache index. > + * @last_index: The final page index (inclusive). > + * @cs: the cachestat struct to write the result to. > + * > + * This will query the page cache statistics of a mapping in the > + * page range of [first_index, last_index] (inclusive). The statistics > + * queried include: number of dirty pages, number of pages marked for > + * writeback, and the number of (recently) evicted pages. > + */ > +void filemap_cachestat(struct address_space *mapping, pgoff_t first_index, > + pgoff_t last_index, struct cachestat *cs) > +{ > + XA_STATE(xas, &mapping->i_pages, first_index); > + struct folio *folio; > + > + rcu_read_lock(); > + xas_for_each(&xas, folio, last_index) { It does not make sense to take more than two ticks to walk the xarray with rcu read lock held. Add stats to mapping instead if CONFIG_CACHESTAT_SYSCALL is enabled, in case of difficulty handling rcu read lock.