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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 3C269C4360F for ; Mon, 1 Apr 2019 14:45:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1185620856 for ; Mon, 1 Apr 2019 14:45:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728695AbfDAOpb (ORCPT ); Mon, 1 Apr 2019 10:45:31 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:38779 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726617AbfDAOpb (ORCPT ); Mon, 1 Apr 2019 10:45:31 -0400 Received: by mail-qt1-f196.google.com with SMTP id d13so11112798qth.5 for ; Mon, 01 Apr 2019 07:45:30 -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=gMWFXOF84tirN8vJJaH4r/H0McFie5EFwhOH5jwK39Q=; b=IT62E++lYX4tpa7y7X3WBotrhGqvSAEZUxKtXuhT7y6Y3pTeOcTOHzDdE/HX2WjLHR fXMJfV177GuoppxZiVFc1uAqPdAcju4e0ynJ9LaJFyQXprKOrhSbJsPlOSHrfTfZxqy9 dwLCnxtibR+GR+p7O+1Q1W+nhZUBJQMVjy8E2WSB6sj8KH0GIOo8U9KASoSt00bqRKyJ dbr0Y7tYcQ6QT2aCj84t9Gw6q8C0MlYpn9SBuXeFFJQBAIWbc+lzAwXJOiKXyI/qcIUJ M7F4tJsJVxjPmeMeuIRqLe/4aFnhj7CVa4ayX0+ShL4a31KvtjDVaU34BRm4Aexv1YrA vWpg== X-Gm-Message-State: APjAAAUrQ7tV8uHVUKow6HV0HouxpUqLAAUqWwWZ7XP4RQiAxcIiiEOL CUlkHQsPtjc3sPd7PZrTp6EtAQ== X-Google-Smtp-Source: APXvYqzJBJY8DrD6iTliprqMc4U5/LFnbB2DPVMUWe0YjnKWLftbU9KgcgwpqYMeNv25dt8ev3bOFA== X-Received: by 2002:a0c:ae04:: with SMTP id y4mr46602243qvc.49.1554129930417; Mon, 01 Apr 2019 07:45:30 -0700 (PDT) Received: from redhat.com (pool-173-76-246-42.bstnma.fios.verizon.net. [173.76.246.42]) by smtp.gmail.com with ESMTPSA id b46sm5053834qtk.77.2019.04.01.07.45.28 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 01 Apr 2019 07:45:29 -0700 (PDT) Date: Mon, 1 Apr 2019 10:45:21 -0400 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: Nitesh Narayan Lal , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, yang.zhang.wz@gmail.com, riel@surriel.com, dodgen@google.com, konrad.wilk@oracle.com, dhildenb@redhat.com, aarcange@redhat.com, alexander.duyck@gmail.com Subject: Re: On guest free page hinting and OOM Message-ID: <20190401104328-mutt-send-email-mst@kernel.org> References: <20190329084058-mutt-send-email-mst@kernel.org> <20190329104311-mutt-send-email-mst@kernel.org> <7a3baa90-5963-e6e2-c862-9cd9cc1b5f60@redhat.com> <20190329125034-mutt-send-email-mst@kernel.org> <20190401073007-mutt-send-email-mst@kernel.org> <29e11829-c9ac-a21b-b2f1-ed833e4ca449@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <29e11829-c9ac-a21b-b2f1-ed833e4ca449@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 01, 2019 at 04:09:32PM +0200, David Hildenbrand wrote: > > > > When you say yield, I would guess that would involve config space access > > to the balloon to flush out outstanding hints? > > I rather meant yield your CPU to the hypervisor, so it can process > hinting requests faster (like waiting for a spinlock). This is the > simple case. More involved approaches might somehow indicate to the > hypervisor to not process queued requests but simply return them to the > guest so the guest can add the isolated pages to the buddy. If this is > "config space access to the balloon to flush out outstanding hints" then > yes, something like that might be a good idea if it doesn't harm > performance. The problem would be in testing this unfortunately. Same as any OOM hack, it is difficult to test well. > -- > > Thanks, > > David / dhildenb