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Mon, 16 Dec 2019 11:45:00 +0000 (UTC) Received: from [10.40.205.109] (ovpn-205-109.brq.redhat.com [10.40.205.109]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2C5ED5C1D6; Mon, 16 Dec 2019 11:44:41 +0000 (UTC) Subject: Re: [PATCH v15 4/7] mm: Introduce Reported pages To: Alexander Duyck , kvm@vger.kernel.org, mst@redhat.com, linux-kernel@vger.kernel.org, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz Cc: yang.zhang.wz@gmail.com, konrad.wilk@oracle.com, david@redhat.com, pagupta@redhat.com, riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com, osalvador@suse.de References: <20191205161928.19548.41654.stgit@localhost.localdomain> <20191205162238.19548.68238.stgit@localhost.localdomain> From: Nitesh Narayan Lal Openpgp: preference=signencrypt Autocrypt: addr=nitesh@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191205162238.19548.68238.stgit@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/5/19 11:22 AM, Alexander Duyck wrote: > From: Alexander Duyck > > In order to pave the way for free page reporting in virtualized > environments we will need a way to get pages out of the free lists and > identify those pages after they have been returned. To accomplish this,= > this patch adds the concept of a Reported Buddy, which is essentially > meant to just be the Uptodate flag used in conjunction with the Buddy > page type. > > To prevent the reported pages from leaking outside of the buddy lists I= > added a check to clear the PageReported bit in the del_page_from_free_l= ist > function. As a result any reported page that is split, merged, or > allocated will have the flag cleared prior to the PageBuddy value being= > cleared. > > The process for reporting pages is fairly simple. Once we free a page t= hat > meets the minimum order for page reporting we will schedule a worker th= read > to start 2s or more in the future. That worker thread will begin workin= g > from the lowest supported page reporting order up to MAX_ORDER - 1 pull= ing > unreported pages from the free list and storing them in the scatterlist= =2E > > When processing each individual free list it is necessary for the worke= r > thread to release the zone lock when it needs to stop and report the fu= ll > scatterlist of pages. To reduce the work of the next iteration the work= er > thread will rotate the free list so that the first unreported page in t= he > free list becomes the first entry in the list. [...] > k); > + > + return err; > +} > + > +static int > +page_reporting_process_zone(struct page_reporting_dev_info *prdev, > + struct scatterlist *sgl, struct zone *zone) > +{ > + unsigned int order, mt, leftover, offset =3D PAGE_REPORTING_CAPACITY;= > + unsigned long watermark; > + int err =3D 0; > + > + /* Generate minimum watermark to be able to guarantee progress */ > + watermark =3D low_wmark_pages(zone) + > + (PAGE_REPORTING_CAPACITY << PAGE_REPORTING_MIN_ORDER); > + > + /* > + * Cancel request if insufficient free memory or if we failed > + * to allocate page reporting statistics for the zone. > + */ > + if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) > + return err; > + Will it not make more sense to check the low watermark condition before e= very reporting request generated for a bunch of 32 isolated pages? or will that be too costly? > + /* Process each free list starting from lowest order/mt */ > + for (order =3D PAGE_REPORTING_MIN_ORDER; order < MAX_ORDER; order++) = { > + for (mt =3D 0; mt < MIGRATE_TYPES; mt++) { > + /* We do not pull pages from the isolate free list */ > + if (is_migrate_isolate(mt)) > + continue; > + > + err =3D page_reporting_cycle(prdev, zone, order, mt, > + sgl, &offset); > + if (err) > + return err; > + } > + } > + > + /* report the leftover pages before going idle */ > + leftover =3D PAGE_REPORTING_CAPACITY - offset; > + if (leftover) { > + sgl =3D &sgl[offset]; > + err =3D prdev->report(prdev, sgl, leftover); > + > + /* flush any remaining pages out from the last report */ > + spin_lock_irq(&zone->lock); > + page_reporting_drain(prdev, sgl, leftover, !err); > + spin_unlock_irq(&zone->lock); > + } > + > + return err; > +} --=20 Nitesh