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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 8C039C433E0 for ; Thu, 4 Jun 2020 15:40:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5BD7320772 for ; Thu, 4 Jun 2020 15:40:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AN3Ft1Bx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729595AbgFDPkK (ORCPT ); Thu, 4 Jun 2020 11:40:10 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:21314 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729542AbgFDPkJ (ORCPT ); Thu, 4 Jun 2020 11:40:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591285207; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=j7Xq9+WeNhyCr/KzEPWJaZZBLidwABLT+Mzl9B23jMM=; b=AN3Ft1BxmCuqVd1eaj7HJlIvgOmtrpCS502CZaapQjNPX1K2DI0X3ImtY9qj768/M1Cozl CFhQLwrKob9zGpxxWolbOgoGAy1XYJxkqFjpYWg76dwLP6OLoa7p4F7Jdf82a85ZAkWBzR YiWqCiPjxQW7PiWwqMBG6+Fj3YT91s0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-156-jNs3Ihj3PECCD929tz65nA-1; Thu, 04 Jun 2020 11:40:05 -0400 X-MC-Unique: jNs3Ihj3PECCD929tz65nA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 211751902EA0; Thu, 4 Jun 2020 15:39:59 +0000 (UTC) Received: from [10.36.112.96] (ovpn-112-96.ams2.redhat.com [10.36.112.96]) by smtp.corp.redhat.com (Postfix) with ESMTP id 850AF60BF4; Thu, 4 Jun 2020 15:39:50 +0000 (UTC) Subject: Re: [RFC v2 7/9] mm/damon: Implement callbacks for physical memory monitoring To: SeongJae Park Cc: akpm@linux-foundation.org, SeongJae Park , Jonathan.Cameron@Huawei.com, aarcange@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, amit@kernel.org, benh@kernel.crashing.org, brendan.d.gregg@gmail.com, brendanhiggins@google.com, cai@lca.pw, colin.king@canonical.com, corbet@lwn.net, dwmw@amazon.com, foersleo@amazon.de, irogers@google.com, jolsa@redhat.com, kirill@shutemov.name, mark.rutland@arm.com, mgorman@suse.de, minchan@kernel.org, mingo@redhat.com, namhyung@kernel.org, peterz@infradead.org, rdunlap@infradead.org, riel@surriel.com, rientjes@google.com, rostedt@goodmis.org, sblbir@amazon.com, shakeelb@google.com, shuah@kernel.org, sj38.park@gmail.com, snu@amazon.de, vbabka@suse.cz, vdavydov.dev@gmail.com, yang.shi@linux.alibaba.com, ying.huang@intel.com, linux-damon@amazon.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200604152336.4826-1-sjpark@amazon.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <3be79702-2ac5-5c5b-b913-3c93aadf0aec@redhat.com> Date: Thu, 4 Jun 2020 17:39:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200604152336.4826-1-sjpark@amazon.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04.06.20 17:23, SeongJae Park wrote: > On Thu, 4 Jun 2020 16:58:13 +0200 David Hildenbrand wrote: > >> On 04.06.20 09:26, SeongJae Park wrote: >>> On Wed, 3 Jun 2020 18:09:21 +0200 David Hildenbrand wrote: >>> >>>> On 03.06.20 16:11, SeongJae Park wrote: >>>>> From: SeongJae Park >>>>> >>>>> This commit implements the four callbacks (->init_target_regions, >>>>> ->update_target_regions, ->prepare_access_check, and ->check_accesses) >>>>> for the basic access monitoring of the physical memory address space. >>>>> By setting the callback pointers to point those, users can easily >>>>> monitor the accesses to the physical memory. >>>>> >>>>> Internally, it uses the PTE Accessed bit, as similar to that of the >>>>> virtual memory support. Also, it supports only page frames that >>>>> supported by idle page tracking. Acutally, most of the code is stollen >>>>> from idle page tracking. Users who want to use other access check >>>>> primitives and monitor the frames that not supported with this >>>>> implementation could implement their own callbacks on their own. >>>>> >>>>> Signed-off-by: SeongJae Park >>>>> --- >>>>> include/linux/damon.h | 5 ++ >>>>> mm/damon.c | 184 ++++++++++++++++++++++++++++++++++++++++++ >>>>> 2 files changed, 189 insertions(+) >>>>> >>>>> diff --git a/include/linux/damon.h b/include/linux/damon.h >>>>> index 1a788bfd1b4e..f96503a532ea 100644 >>>>> --- a/include/linux/damon.h >>>>> +++ b/include/linux/damon.h >>>>> @@ -216,6 +216,11 @@ void kdamond_update_vm_regions(struct damon_ctx *ctx); >>>>> void kdamond_prepare_vm_access_checks(struct damon_ctx *ctx); >>>>> unsigned int kdamond_check_vm_accesses(struct damon_ctx *ctx); >>>>> >>>>> +void kdamond_init_phys_regions(struct damon_ctx *ctx); >>>>> +void kdamond_update_phys_regions(struct damon_ctx *ctx); >>>>> +void kdamond_prepare_phys_access_checks(struct damon_ctx *ctx); >>>>> +unsigned int kdamond_check_phys_accesses(struct damon_ctx *ctx); >>>>> + >>>>> int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids); >>>>> int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int, >>>>> unsigned long aggr_int, unsigned long regions_update_int, >>>>> diff --git a/mm/damon.c b/mm/damon.c >>>>> index f5cbc97a3bbc..6a5c6d540580 100644 >>>>> --- a/mm/damon.c >>>>> +++ b/mm/damon.c >>>>> @@ -19,7 +19,9 @@ >>>>> #include >>>>> #include >>>>> #include >>>>> +#include >>>>> #include >>>>> +#include >>>>> #include >>>>> #include >>>>> #include >>>>> @@ -480,6 +482,11 @@ void kdamond_init_vm_regions(struct damon_ctx *ctx) >>>>> } >>>>> } >>>>> >>>>> +/* Do nothing. Users should set the initial regions by themselves */ >>>>> +void kdamond_init_phys_regions(struct damon_ctx *ctx) >>>>> +{ >>>>> +} >>>>> + >>>>> static void damon_mkold(struct mm_struct *mm, unsigned long addr) >>>>> { >>>>> pte_t *pte = NULL; >>>>> @@ -611,6 +618,178 @@ unsigned int kdamond_check_vm_accesses(struct damon_ctx *ctx) >>>>> return max_nr_accesses; >>>>> } >>>>> >>>>> +/* access check functions for physical address based regions */ >>>>> + >>>>> +/* This code is stollen from page_idle.c */ >>>>> +static struct page *damon_phys_get_page(unsigned long pfn) >>>>> +{ >>>>> + struct page *page; >>>>> + pg_data_t *pgdat; >>>>> + >>>>> + if (!pfn_valid(pfn)) >>>>> + return NULL; >>>>> + >>>> >>>> Who provides these pfns? Can these be random pfns, supplied unchecked by >>>> user space? Or are they at least mapped into some user space process? >>> >>> Your guess is right, users can give random physical address and that will be >>> translated into pfn. >>> >> >> Note the difference to idle tracking: "Idle page tracking only considers >> user memory pages", this is very different to your use case. Note that >> this is why there is no pfn_to_online_page() check in page idle code. > > My use case is same to that of idle page. I also ignore non-user pages. > Actually, this function is for filtering of the non-user pages, which is simply > stollen from the page_idle. Okay, that is valuable information, I missed that. The comment in page_idle.c is actually pretty valuable. In both cases, user space can provide random physical address but you will only care about user pages. Understood. That turns things less dangerous. :) >>>> IOW, do we need a pfn_to_online_page() to make sure the memmap even was >>>> initialized? >>> >>> Thank you for pointing out this! I will use it in the next spin. Also, this >>> code is stollen from page_idle_get_page(). Seems like it should also be >>> modified to use it. I will send the patch for it, either. >> >> pfn_to_online_page() will only succeed for system RAM pages, not >> dax/pmem (ZONE_DEVICE). dax/pmem needs special care. >> >> I can spot that you are taking references to random struct pages. This >> looks dangerous to me and might mess in complicated ways with page >> migration/isolation/onlining/offlining etc. I am not sure if we want that. > > AFAIU, page_idle users can also pass random pfns by randomly accessing the > bitmap file. Am I missing something? I am definitely no expert on page idle tracking. If that is the case, then we'll also need pfn_to_online_page() handling (and might have to care about ZONE_DEVICE, not hard but needs some extra LOCs). I am still not sure if grabbing references on theoretically isolated pageblocks is okay, but that's just complicated stuff and as you state, is already performed. At least I can read "With such an indicator of user pages we can skip isolated pages". So isolated pages during page migration are properly handled. Instead of stealing, factor out, document, and reuse? That makes it clearer that you are not inventing the wheel, and if we have to fix something, we only have to fix at a single point. -- Thanks, David / dhildenb