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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 949F1C76186 for ; Wed, 24 Jul 2019 19:24:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64EE32238C for ; Wed, 24 Jul 2019 19:24:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387982AbfGXTYs (ORCPT ); Wed, 24 Jul 2019 15:24:48 -0400 Received: from mail-qk1-f196.google.com ([209.85.222.196]:40171 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387551AbfGXTYo (ORCPT ); Wed, 24 Jul 2019 15:24:44 -0400 Received: by mail-qk1-f196.google.com with SMTP id s145so34624703qke.7 for ; Wed, 24 Jul 2019 12:24:44 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=6wfpg22kkBGQSGagL3FHOCSJzZUomxdfgUX443/VLoE=; b=c5nMOTVW0zL64A8i8hpz6SfSI8If5z42EAC6X2ZtOOeIG0WKMZvs5etsCTpchk6CFc 1yrz9mJ9cYFMg1gnWfELTjUNt4QdhtQfKOUE8W7BPia4m4L0uXZzeHIp/L93OHIfx5+s wvrFP9vGXDkF9Alu1/xeRHOmCuKChHrzTXdDCIVJN9KO2mvc446Cdgat6A+/kCd6zPs/ FXECLYjasl0GJbPi7VtzbA42O6W4/XS8XH/OqOEiKo4q6T8y7+ooZZ7fG8RuVAMCrzHx OljhOmeZGFN7GrhbQqE499lpHVz2sxmbKW/awt22WSrbqi7qosPHrOyXxX1os+b1LGw6 470g== X-Gm-Message-State: APjAAAWbpcpr7nfeYSWxUOVbEpqrcqA5+SFTVlQ+e24RcD4RGi9zF916 2JFfsZiQIOmtyoZZ8yqa+4W6IQ== X-Google-Smtp-Source: APXvYqy77kkB2RpSxBnWenjZ0UwyhE7LKJGBKOCJhGTtIhJgVV+u7LlioVLo64z1RecpigW2GqU0Mw== X-Received: by 2002:a37:ac19:: with SMTP id e25mr56019402qkm.155.1563996283591; Wed, 24 Jul 2019 12:24:43 -0700 (PDT) Received: from redhat.com (bzq-79-181-91-42.red.bezeqint.net. [79.181.91.42]) by smtp.gmail.com with ESMTPSA id j6sm3007749qtl.85.2019.07.24.12.24.38 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 24 Jul 2019 12:24:42 -0700 (PDT) Date: Wed, 24 Jul 2019 15:24:35 -0400 From: "Michael S. Tsirkin" To: Nitesh Narayan Lal Cc: Alexander Duyck , kvm@vger.kernel.org, david@redhat.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, yang.zhang.wz@gmail.com, pagupta@redhat.com, riel@surriel.com, konrad.wilk@oracle.com, lcapitulino@redhat.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com Subject: Re: [PATCH v2 0/5] mm / virtio: Provide support for page hinting Message-ID: <20190724151855-mutt-send-email-mst@kernel.org> References: <20190724165158.6685.87228.stgit@localhost.localdomain> <0c520470-4654-cdf2-cf4d-d7c351d25e8b@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0c520470-4654-cdf2-cf4d-d7c351d25e8b@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 24, 2019 at 02:40:02PM -0400, Nitesh Narayan Lal wrote: > > On 7/24/19 12:54 PM, Alexander Duyck wrote: > > This series provides an asynchronous means of hinting to a hypervisor > > that a guest page is no longer in use and can have the data associated > > with it dropped. To do this I have implemented functionality that allows > > for what I am referring to as page hinting > > > > The functionality for this is fairly simple. When enabled it will allocate > > statistics to track the number of hinted pages in a given free area. When > > the number of free pages exceeds this value plus a high water value, > > currently 32, > Shouldn't we configure this to a lower number such as 16? > > it will begin performing page hinting which consists of > > pulling pages off of free list and placing them into a scatter list. The > > scatterlist is then given to the page hinting device and it will perform > > the required action to make the pages "hinted", in the case of > > virtio-balloon this results in the pages being madvised as MADV_DONTNEED > > and as such they are forced out of the guest. After this they are placed > > back on the free list, and an additional bit is added if they are not > > merged indicating that they are a hinted buddy page instead of a standard > > buddy page. The cycle then repeats with additional non-hinted pages being > > pulled until the free areas all consist of hinted pages. > > > > I am leaving a number of things hard-coded such as limiting the lowest > > order processed to PAGEBLOCK_ORDER, > Have you considered making this option configurable at the compile time? > > and have left it up to the guest to > > determine what the limit is on how many pages it wants to allocate to > > process the hints. > It might make sense to set the number of pages to be hinted at a time from the > hypervisor. > > > > My primary testing has just been to verify the memory is being freed after > > allocation by running memhog 79g on a 80g guest and watching the total > > free memory via /proc/meminfo on the host. With this I have verified most > > of the memory is freed after each iteration. As far as performance I have > > been mainly focusing on the will-it-scale/page_fault1 test running with > > 16 vcpus. With that I have seen at most a 2% difference between the base > > kernel without these patches and the patches with virtio-balloon disabled. > > With the patches and virtio-balloon enabled with hinting the results > > largely depend on the host kernel. On a 3.10 RHEL kernel I saw up to a 2% > > drop in performance as I approached 16 threads, > I think this is acceptable. > > however on the the lastest > > linux-next kernel I saw roughly a 4% to 5% improvement in performance for > > all tests with 8 or more threads. > Do you mean that with your patches the will-it-scale/page_fault1 numbers were > better by 4-5% over an unmodified kernel? > > I believe the difference seen is due to > > the overhead for faulting pages back into the guest and zeroing of memory. > It may also make sense to test these patches with netperf to observe how much > performance drop it is introducing. > > Patch 4 is a bit on the large side at about 600 lines of change, however > > I really didn't see a good way to break it up since each piece feeds into > > the next. So I couldn't add the statistics by themselves as it didn't > > really make sense to add them without something that will either read or > > increment/decrement them, or add the Hinted state without something that > > would set/unset it. As such I just ended up adding the entire thing as > > one patch. It makes it a bit bigger but avoids the issues in the previous > > set where I was referencing things before they had been added. > > > > Changes from the RFC: > > https://lore.kernel.org/lkml/20190530215223.13974.22445.stgit@localhost.localdomain/ > > Moved aeration requested flag out of aerator and into zone->flags. > > Moved bounary out of free_area and into local variables for aeration. > > Moved aeration cycle out of interrupt and into workqueue. > > Left nr_free as total pages instead of splitting it between raw and aerated. > > Combined size and physical address values in virtio ring into one 64b value. > > > > Changes from v1: > > https://lore.kernel.org/lkml/20190619222922.1231.27432.stgit@localhost.localdomain/ > > Dropped "waste page treatment" in favor of "page hinting" > We may still have to try and find a better name for virtio-balloon side changes. > As "FREE_PAGE_HINT" and "PAGE_HINTING" are still confusing. Right. In fact I'm not sure why should these be called hints at all. VIRTIO_BALLOON_F_FREE_PAGE_HINT is a hint because pages might no longer be free by the time they are reported. I think of this one as a free page reporting capability. I don't really mind how are internal kernel functions called, but I think for virtio uapi things that's a better name. > > Renamed files and functions from "aeration" to "page_hinting" > > Moved from page->lru list to scatterlist > > Replaced wait on refcnt in shutdown with RCU and cancel_delayed_work_sync > > Virtio now uses scatterlist directly instead of intermedate array > > Moved stats out of free_area, now in seperate area and pointed to from zone > > Merged patch 5 into patch 4 to improve reviewability > > Updated various code comments throughout > > > > --- > > > > Alexander Duyck (5): > > mm: Adjust shuffle code to allow for future coalescing > > mm: Move set/get_pcppage_migratetype to mmzone.h > > mm: Use zone and order instead of free area in free_list manipulators > > mm: Introduce Hinted pages > > virtio-balloon: Add support for providing page hints to host > > > > > > drivers/virtio/Kconfig | 1 > > drivers/virtio/virtio_balloon.c | 47 ++++++ > > include/linux/mmzone.h | 116 ++++++++------ > > include/linux/page-flags.h | 8 + > > include/linux/page_hinting.h | 139 ++++++++++++++++ > > include/uapi/linux/virtio_balloon.h | 1 > > mm/Kconfig | 5 + > > mm/Makefile | 1 > > mm/internal.h | 18 ++ > > mm/memory_hotplug.c | 1 > > mm/page_alloc.c | 238 ++++++++++++++++++++-------- > > mm/page_hinting.c | 298 +++++++++++++++++++++++++++++++++++ > > mm/shuffle.c | 24 --- > > mm/shuffle.h | 32 ++++ > > 14 files changed, 796 insertions(+), 133 deletions(-) > > create mode 100644 include/linux/page_hinting.h > > create mode 100644 mm/page_hinting.c > > > > -- > -- > Thanks > Nitesh