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=-17.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 AADE9C433E0 for ; Thu, 4 Feb 2021 23:15:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4027464FA1 for ; Thu, 4 Feb 2021 23:15:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4027464FA1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 82E7A6B0006; Thu, 4 Feb 2021 18:14:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7DEF06B006C; Thu, 4 Feb 2021 18:14:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F4CD6B006E; Thu, 4 Feb 2021 18:14:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0250.hostedemail.com [216.40.44.250]) by kanga.kvack.org (Postfix) with ESMTP id 599D56B0006 for ; Thu, 4 Feb 2021 18:14:59 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 1BD13181AEF10 for ; Thu, 4 Feb 2021 23:14:59 +0000 (UTC) X-FDA: 77782142718.21.land17_5f1011f275e0 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id E5CA9180442C2 for ; Thu, 4 Feb 2021 23:14:58 +0000 (UTC) X-HE-Tag: land17_5f1011f275e0 X-Filterd-Recvd-Size: 8344 Received: from hqnvemgate25.nvidia.com (hqnvemgate25.nvidia.com [216.228.121.64]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Thu, 4 Feb 2021 23:14:58 +0000 (UTC) Received: from hqmail.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, AES256-SHA) id ; Thu, 04 Feb 2021 15:14:56 -0800 Received: from [10.2.60.31] (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 4 Feb 2021 23:14:56 +0000 Subject: Re: [PATCH] mm: cma: support sysfs To: Minchan Kim CC: Andrew Morton , , , , LKML , linux-mm References: <20210203155001.4121868-1-minchan@kernel.org> <7e7c01a7-27fe-00a3-f67f-8bcf9ef3eae9@nvidia.com> From: John Hubbard Message-ID: Date: Thu, 4 Feb 2021 15:14:56 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:85.0) Gecko/20100101 Thunderbird/85.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1612480496; bh=iqnibRkYMND2LBnZbq/+jRw2sNbA9oNqdLngUy4ZkT8=; h=Subject:To:CC:References:From:Message-ID:Date:User-Agent: MIME-Version:In-Reply-To:Content-Type:Content-Language: Content-Transfer-Encoding:X-Originating-IP:X-ClientProxiedBy; b=lOQmXxgbPMLjByuaPuVNzhVTJdzp0Do2wpkAvlQqFQsojrvGX9CBVTqLpZzFgc1UZ uPSaQNnEUjXgPrfNyXsUAAh0NF05LVzGizVJyVZLUbRNjyAq4+rdV4psMO9KSOJOS+ 7HhFFLgaA5t8KeZokZUew0anjhKYyAFX2NX2JN9nw0iQ8lOYByeA4UIeD+mlAQCOtY fV8ArNCTukWx/Ty2JOM3c42JRwHPBskOamE45Ef2dL+VT+JQHQotUwkjt53tW1xMi2 gIP/m0ukY0+oWFt6bGhcZ8zxNp88GmkbZobStdcm3ED2o/V+TaQsf+pX2iXxPt7o4/ CmEs47lxRMoQA== 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 2/4/21 12:07 PM, Minchan Kim wrote: > On Thu, Feb 04, 2021 at 12:50:58AM -0800, John Hubbard wrote: >> On 2/3/21 7:50 AM, Minchan Kim wrote: >>> Since CMA is getting used more widely, it's more important to >>> keep monitoring CMA statistics for system health since it's >>> directly related to user experience. >>> >>> This patch introduces sysfs for the CMA and exposes stats below >>> to keep monitor for telemetric in the system. >>> >>> * the number of CMA allocation attempts >>> * the number of CMA allocation failures >>> * the number of CMA page allocation attempts >>> * the number of CMA page allocation failures >> >> The desire to report CMA data is understandable, but there are a few >> odd things here: >> >> 1) First of all, this has significant overlap with /sys/kernel/debug/cma >> items. I suspect that all of these items could instead go into > > At this moment, I don't see any overlap with item from cma_debugfs. > Could you specify what item you are mentioning? Just the fact that there would be two systems under /sys, both of which are doing very very similar things: providing information that is intended to help diagnose CMA. > >> /sys/kernel/debug/cma, right? > > Anyway, thing is I need an stable interface for that and need to use > it in Android production build, too(Unfortunately, Android deprecated > the debugfs > https://source.android.com/setup/start/android-11-release#debugfs > ) That's the closest hint to a "why this is needed" that we've seen yet. But it's only a hint. > > What should be in debugfs and in sysfs? What's the criteria? Well, it's a gray area. "Debugging support" goes into debugfs, and "production-level monitoring and control" goes into sysfs, roughly speaking. And here you have items that could be classified as either. > > Some statistic could be considered about debugging aid or telemetric > depening on view point and usecase. And here, I want to use it for > telemetric, get an stable interface and use it in production build > of Android. In this chance, I'd like to get concrete guideline > what should be in sysfs and debugfs so that pointing out this thread > whenever folks dump their stat into sysfs to avoid waste of time > for others in future. :) > >> >> 2) The overall CMA allocation attempts/failures (first two items above) seem >> an odd pair of things to track. Maybe that is what was easy to track, but I'd >> vote for just omitting them. > > Then, how to know how often CMA API failed? Why would you even need to know that, *in addition* to knowing specific page allocation numbers that failed? Again, there is no real-world motivation cited yet, just "this is good data". Need more stories and support here. thanks, -- John Hubbard NVIDIA > There are various size allocation request for a CMA so only page > allocation stat are not enough to know it. > >>> >>> Signed-off-by: Minchan Kim >>> --- >>> Documentation/ABI/testing/sysfs-kernel-mm-cma | 39 +++++ >>> include/linux/cma.h | 1 + >>> mm/Makefile | 1 + >>> mm/cma.c | 6 +- >>> mm/cma.h | 20 +++ >>> mm/cma_sysfs.c | 143 ++++++++++++++++++ >>> 6 files changed, 209 insertions(+), 1 deletion(-) >>> create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-cma >>> create mode 100644 mm/cma_sysfs.c >>> >>> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-cma b/Documentation/ABI/testing/sysfs-kernel-mm-cma >>> new file mode 100644 >>> index 000000000000..2a43c0aacc39 >>> --- /dev/null >>> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-cma >>> @@ -0,0 +1,39 @@ >>> +What: /sys/kernel/mm/cma/ >>> +Date: Feb 2021 >>> +Contact: Minchan Kim >>> +Description: >>> + /sys/kernel/mm/cma/ contains a number of subdirectories by >>> + cma-heap name. The subdirectory contains a number of files >>> + to represent cma allocation statistics. >> >> Somewhere, maybe here, there should be a mention of the closely related >> /sys/kernel/debug/cma files. >> >>> + >>> + There are number of files under >>> + /sys/kernel/mm/cma/ directory >>> + >>> + - cma_alloc_attempt >>> + - cma_alloc_fail >> >> Are these really useful? They a summary of the alloc_pages items, really. >> >>> + - alloc_pages_attempt >>> + - alloc_pages_fail >> >> This should also have "cma" in the name, really: cma_alloc_pages_*. > > No problem. > >> >>> + >>> +What: /sys/kernel/mm/cma//cma_alloc_attempt >>> +Date: Feb 2021 >>> +Contact: Minchan Kim >>> +Description: >>> + the number of cma_alloc API attempted >>> + >>> +What: /sys/kernel/mm/cma//cma_alloc_fail >>> +Date: Feb 2021 >>> +Contact: Minchan Kim >>> +Description: >>> + the number of CMA_alloc API failed >>> + >>> +What: /sys/kernel/mm/cma//alloc_pages_attempt >>> +Date: Feb 2021 >>> +Contact: Minchan Kim >>> +Description: >>> + the number of pages CMA API tried to allocate >>> + >>> +What: /sys/kernel/mm/cma//alloc_pages_fail >>> +Date: Feb 2021 >>> +Contact: Minchan Kim >>> +Description: >>> + the number of pages CMA API failed to allocate >>> diff --git a/include/linux/cma.h b/include/linux/cma.h >>> index 217999c8a762..71a28a5bb54e 100644 >>> --- a/include/linux/cma.h >>> +++ b/include/linux/cma.h >>> @@ -49,4 +49,5 @@ extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align, >>> extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count); >>> extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data); >>> + >> >> A single additional blank line seems to be the only change to this file. :) > > Oops. >