To: wei.w.wang@intel.com, willy@infradead.org
Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org,
        qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org,
        kvm@vger.kernel.org, linux-mm@kvack.org, mst@redhat.com,
        mhocko@kernel.org, akpm@linux-foundation.org,
        mawilcox@microsoft.com, david@redhat.com, cornelia.huck@de.ibm.com,
        mgorman@techsingularity.net, aarcange@redhat.com,
        amit.shah@redhat.com, pbonzini@redhat.com,
        liliang.opensource@gmail.com, yang.zhang.wz@gmail.com,
        quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com
Subject: Re: [PATCH v20 4/7] virtio-balloon: VIRTIO_BALLOON_F_SG
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
References: <201712241345.DIG21823.SLFOOJtQFOMVFH@I-love.SAKURA.ne.jp>
        <5A3F5A4A.1070009@intel.com>
        <20180102132419.GB8222@bombadil.infradead.org>
        <201801031129.JFC18298.FJMHtOFLVSQOFO@I-love.SAKURA.ne.jp>
        <5A4C9BAC.3040808@intel.com>
In-Reply-To: <5A4C9BAC.3040808@intel.com>
Message-Id: <201801031918.GGJ69207.JOFSHQLMFtVOFO@I-love.SAKURA.ne.jp>
Date: Wed, 3 Jan 2018 19:19:00 +0900
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Sender: linux-kernel-owner@vger.kernel.org

Wei Wang wrote:
> On 01/03/2018 10:29 AM, Tetsuo Handa wrote:
> > Matthew Wilcox wrote:
> >> The radix tree convention is objectively awful, which is why I'm working
> >> to change it.  Specifying the GFP flags at radix tree initialisation time
> >> rather than allocation time leads to all kinds of confusion.  The preload
> >> API is a pretty awful workaround, and it will go away once the XArray
> >> is working correctly.  That said, there's no alternative to it without
> >> making XBitmap depend on XArray, and I don't want to hold you up there.
> >> So there's an xb_preload for the moment.
> > I'm ready to propose cvbmp shown below as an alternative to xbitmap (but
> > specialized for virtio-balloon case). Wei, can you do some benchmarking
> > between xbitmap and cvbmp?
> > ----------------------------------------
> > cvbmp: clustered values bitmap
> 
> I don't think we need to replace xbitmap, at least at this stage. The 
> new implementation doesn't look simpler at all, and virtio-balloon has 
> worked well with xbitmap.
> 
> I would suggest you to send out the new implementation for discussion 
> after this series ends, and justify with better performance results if 
> you could get.

I'm VMware Workstation Player user, and I don't have environment for doing
performance test using virtio-balloon. Thus, I need to ask you.

Also, please look at
http://lkml.kernel.org/r/1514904621-39186-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp .