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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 B406EC433FF for ; Tue, 13 Aug 2019 10:31:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8169220679 for ; Tue, 13 Aug 2019 10:31:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727321AbfHMKbB convert rfc822-to-8bit (ORCPT ); Tue, 13 Aug 2019 06:31:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57712 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726360AbfHMKbA (ORCPT ); Tue, 13 Aug 2019 06:31:00 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 88385C015C30; Tue, 13 Aug 2019 10:30:59 +0000 (UTC) Received: from [10.40.204.186] (ovpn-204-186.brq.redhat.com [10.40.204.186]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AE1C786BAE; Tue, 13 Aug 2019 10:30:45 +0000 (UTC) Subject: Re: [RFC][Patch v12 1/2] mm: page_reporting: core infrastructure To: David Hildenbrand , Alexander Duyck Cc: kvm list , LKML , linux-mm , virtio-dev@lists.oasis-open.org, Paolo Bonzini , lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, Yang Zhang , Rik van Riel , "Michael S. Tsirkin" , dodgen@google.com, Konrad Rzeszutek Wilk , dhildenb@redhat.com, Andrea Arcangeli , john.starks@microsoft.com, Dave Hansen , Michal Hocko , cohuck@redhat.com References: <20190812131235.27244-1-nitesh@redhat.com> <20190812131235.27244-2-nitesh@redhat.com> From: Nitesh Narayan Lal Openpgp: preference=signencrypt Autocrypt: addr=nitesh@redhat.com; prefer-encrypt=mutual; keydata= mQINBFl4pQoBEADT/nXR2JOfsCjDgYmE2qonSGjkM1g8S6p9UWD+bf7YEAYYYzZsLtbilFTe z4nL4AV6VJmC7dBIlTi3Mj2eymD/2dkKP6UXlliWkq67feVg1KG+4UIp89lFW7v5Y8Muw3Fm uQbFvxyhN8n3tmhRe+ScWsndSBDxYOZgkbCSIfNPdZrHcnOLfA7xMJZeRCjqUpwhIjxQdFA7 n0s0KZ2cHIsemtBM8b2WXSQG9CjqAJHVkDhrBWKThDRF7k80oiJdEQlTEiVhaEDURXq+2XmG jpCnvRQDb28EJSsQlNEAzwzHMeplddfB0vCg9fRk/kOBMDBtGsTvNT9OYUZD+7jaf0gvBvBB lbKmmMMX7uJB+ejY7bnw6ePNrVPErWyfHzR5WYrIFUtgoR3LigKnw5apzc7UIV9G8uiIcZEn C+QJCK43jgnkPcSmwVPztcrkbC84g1K5v2Dxh9amXKLBA1/i+CAY8JWMTepsFohIFMXNLj+B RJoOcR4HGYXZ6CAJa3Glu3mCmYqHTOKwezJTAvmsCLd3W7WxOGF8BbBjVaPjcZfavOvkin0u DaFvhAmrzN6lL0msY17JCZo046z8oAqkyvEflFbC0S1R/POzehKrzQ1RFRD3/YzzlhmIowkM BpTqNBeHEzQAlIhQuyu1ugmQtfsYYq6FPmWMRfFPes/4JUU/PQARAQABtCVOaXRlc2ggTmFy YXlhbiBMYWwgPG5pbGFsQHJlZGhhdC5jb20+iQI9BBMBCAAnBQJZeKUKAhsjBQkJZgGABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEKOGQNwGMqM56lEP/A2KMs/pu0URcVk/kqVwcBhU SnvB8DP3lDWDnmVrAkFEOnPX7GTbactQ41wF/xwjwmEmTzLrMRZpkqz2y9mV0hWHjqoXbOCS 6RwK3ri5e2ThIPoGxFLt6TrMHgCRwm8YuOSJ97o+uohCTN8pmQ86KMUrDNwMqRkeTRW9wWIQ EdDqW44VwelnyPwcmWHBNNb1Kd8j3xKlHtnS45vc6WuoKxYRBTQOwI/5uFpDZtZ1a5kq9Ak/ MOPDDZpd84rqd+IvgMw5z4a5QlkvOTpScD21G3gjmtTEtyfahltyDK/5i8IaQC3YiXJCrqxE r7/4JMZeOYiKpE9iZMtS90t4wBgbVTqAGH1nE/ifZVAUcCtycD0f3egX9CHe45Ad4fsF3edQ ESa5tZAogiA4Hc/yQpnnf43a3aQ67XPOJXxS0Qptzu4vfF9h7kTKYWSrVesOU3QKYbjEAf95 NewF9FhAlYqYrwIwnuAZ8TdXVDYt7Z3z506//sf6zoRwYIDA8RDqFGRuPMXUsoUnf/KKPrtR ceLcSUP/JCNiYbf1/QtW8S6Ca/4qJFXQHp0knqJPGmwuFHsarSdpvZQ9qpxD3FnuPyo64S2N Dfq8TAeifNp2pAmPY2PAHQ3nOmKgMG8Gn5QiORvMUGzSz8Lo31LW58NdBKbh6bci5+t/HE0H pnyVf5xhNC/FuQINBFl4pQoBEACr+MgxWHUP76oNNYjRiNDhaIVtnPRqxiZ9v4H5FPxJy9UD Bqr54rifr1E+K+yYNPt/Po43vVL2cAyfyI/LVLlhiY4yH6T1n+Di/hSkkviCaf13gczuvgz4 KVYLwojU8+naJUsiCJw01MjO3pg9GQ+47HgsnRjCdNmmHiUQqksMIfd8k3reO9SUNlEmDDNB XuSzkHjE5y/R/6p8uXaVpiKPfHoULjNRWaFc3d2JGmxJpBdpYnajoz61m7XJlgwl/B5Ql/6B dHGaX3VHxOZsfRfugwYF9CkrPbyO5PK7yJ5vaiWre7aQ9bmCtXAomvF1q3/qRwZp77k6i9R3 tWfXjZDOQokw0u6d6DYJ0Vkfcwheg2i/Mf/epQl7Pf846G3PgSnyVK6cRwerBl5a68w7xqVU 4KgAh0DePjtDcbcXsKRT9D63cfyfrNE+ea4i0SVik6+N4nAj1HbzWHTk2KIxTsJXypibOKFX 2VykltxutR1sUfZBYMkfU4PogE7NjVEU7KtuCOSAkYzIWrZNEQrxYkxHLJsWruhSYNRsqVBy KvY6JAsq/i5yhVd5JKKU8wIOgSwC9P6mXYRgwPyfg15GZpnw+Fpey4bCDkT5fMOaCcS+vSU1 UaFmC4Ogzpe2BW2DOaPU5Ik99zUFNn6cRmOOXArrryjFlLT5oSOe4IposgWzdwARAQABiQIl BBgBCAAPBQJZeKUKAhsMBQkJZgGAAAoJEKOGQNwGMqM5ELoP/jj9d9gF1Al4+9bngUlYohYu 0sxyZo9IZ7Yb7cHuJzOMqfgoP4tydP4QCuyd9Q2OHHL5AL4VFNb8SvqAxxYSPuDJTI3JZwI7 d8JTPKwpulMSUaJE8ZH9n8A/+sdC3CAD4QafVBcCcbFe1jifHmQRdDrvHV9Es14QVAOTZhnJ vweENyHEIxkpLsyUUDuVypIo6y/Cws+EBCWt27BJi9GH/EOTB0wb+2ghCs/i3h8a+bi+bS7L FCCm/AxIqxRurh2UySn0P/2+2eZvneJ1/uTgfxnjeSlwQJ1BWzMAdAHQO1/lnbyZgEZEtUZJ x9d9ASekTtJjBMKJXAw7GbB2dAA/QmbA+Q+Xuamzm/1imigz6L6sOt2n/X/SSc33w8RJUyor SvAIoG/zU2Y76pKTgbpQqMDmkmNYFMLcAukpvC4ki3Sf086TdMgkjqtnpTkEElMSFJC8npXv 3QnGGOIfFug/qs8z03DLPBz9VYS26jiiN7QIJVpeeEdN/LKnaz5LO+h5kNAyj44qdF2T2AiF HxnZnxO5JNP5uISQH3FjxxGxJkdJ8jKzZV7aT37sC+Rp0o3KNc+GXTR+GSVq87Xfuhx0LRST NK9ZhT0+qkiN7npFLtNtbzwqaqceq3XhafmCiw8xrtzCnlB/C4SiBr/93Ip4kihXJ0EuHSLn VujM7c/b4pps Organization: Red Hat Inc, Message-ID: Date: Tue, 13 Aug 2019 06:30:41 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 13 Aug 2019 10:30:59 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 8/12/19 4:05 PM, David Hildenbrand wrote: >>> --- >>> include/linux/mmzone.h | 11 ++ >>> include/linux/page_reporting.h | 63 +++++++ >>> mm/Kconfig | 6 + >>> mm/Makefile | 1 + >>> mm/page_alloc.c | 42 ++++- >>> mm/page_reporting.c | 332 +++++++++++++++++++++++++++++++++ >>> 6 files changed, 448 insertions(+), 7 deletions(-) >>> create mode 100644 include/linux/page_reporting.h >>> create mode 100644 mm/page_reporting.c >>> >>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >>> index d77d717c620c..ba5f5b508f25 100644 >>> --- a/include/linux/mmzone.h >>> +++ b/include/linux/mmzone.h >>> @@ -559,6 +559,17 @@ struct zone { >>> /* Zone statistics */ >>> atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS]; >>> atomic_long_t vm_numa_stat[NR_VM_NUMA_STAT_ITEMS]; >>> +#ifdef CONFIG_PAGE_REPORTING >>> + /* Pointer to the bitmap in PAGE_REPORTING_MIN_ORDER granularity */ >>> + unsigned long *bitmap; >>> + /* Preserve start and end PFN in case they change due to hotplug */ >>> + unsigned long base_pfn; >>> + unsigned long end_pfn; >>> + /* Free pages of granularity PAGE_REPORTING_MIN_ORDER */ >>> + atomic_t free_pages; >>> + /* Number of bits required in the bitmap */ >>> + unsigned long nbits; >>> +#endif >>> } ____cacheline_internodealigned_in_smp; >> Okay, so the original thing this patch set had going for it was that >> it was non-invasive. However, now you are adding a bunch of stuff to >> the zone. That kind of loses the non-invasive argument for this patch >> set compared to mine. >> > Adding something to "struct zone" is certainly less invasive than core > buddy modifications, just saying (I agree that this is suboptimal. I > would have guessed that all that's needed is a pointer to some private > structure here). I think having just a pointer to a private structure makes sense here. If I am not wrong then I can probably make an allocation for it for each populated zone at the time I enable page reporting. > However, the migratetype thingy below looks fishy to me. > >> If we are going to continue further with this patch set then it might >> be worth looking into dynamically allocating the space you need for >> this block. At a minimum you could probably look at making the bitmap >> an RCU based setup so you could define the base and end along with the >> bitmap. It would probably help to resolve the hotplug issues you still >> need to address. > Yeah, I guess that makes sense. > > [...] >>> + >>> +static int process_free_page(struct page *page, >>> + struct page_reporting_config *phconf, int count) >>> +{ >>> + int mt, order, ret = 0; >>> + >>> + mt = get_pageblock_migratetype(page); >>> + order = page_private(page); >>> + ret = __isolate_free_page(page, order); >>> + > I just started looking into the wonderful world of > isolation/compaction/migration. > > I don't think saving/restoring the migratetype is correct here. AFAIK, > MOVABLE/UNMOVABLE/RECLAIMABLE is just a hint, doesn't mean that e.g., > movable pages and up in UNMOVABLE or ordinary kernel allocations on > MOVABLE. So that shouldn't be an issue - I guess. > > 1. You should never allocate something that is no > MOVABLE/UNMOVABLE/RECLAIMABLE. Especially not, if you have ISOLATE or > CMA here. There should at least be a !is_migrate_isolate_page() check > somewhere > > 2. set_migratetype_isolate() takes the zone lock, so to avoid racing > with isolation code, you have to hold the zone lock. Your code seems to > do that, so at least you cannot race against isolation. > > 3. You could end up temporarily allocating something in the > ZONE_MOVABLE. The pages you allocate are, however, not movable. There > would have to be a way to make alloc_contig_range()/offlining code > properly wait until the pages have been processed. Not sure about the > real implications, though - too many details in the code (I wonder if > Alex' series has a way of dealing with that) > > When you restore the migratetype, you could suddenly overwrite e.g., > ISOLATE, which feels wrong. I was triggering an occasional CPU stall bug earlier, with saving and restoring the migratetype I was able to fix it. But I will further look into this to figure out if it is really required. > [...] >> So as per your comments in the cover page, the two functions above >> should also probably be plugged into the zone resizing logic somewhere >> so if a zone is resized the bitmap is adjusted. >> >>> +/** >>> + * zone_reporting_init - For each zone initializes the page reporting fields >>> + * and allocates the respective bitmap. >>> + * >>> + * This function returns 0 on successful initialization, -ENOMEM otherwise. >>> + */ >>> +static int zone_reporting_init(void) >>> +{ >>> + struct zone *zone; >>> + int ret; >>> + >>> + for_each_populated_zone(zone) { >>> +#ifdef CONFIG_ZONE_DEVICE >>> + /* we can not report pages which are not in the buddy */ >>> + if (zone_idx(zone) == ZONE_DEVICE) >>> + continue; >>> +#endif >> I'm pretty sure this isn't needed since I don't think the ZONE_DEVICE >> zone will be considered "populated". >> > I think you are right (although it's confusing, we will have present > sections part of a zone but the zone has no present_pages - screams like > a re factoring - leftover from ZONE_DEVICE introduction). I think in that case it is safe to have this check here. What do you guys suggest? > -- Thanks Nitesh