From: Michal Hocko <mhocko@kernel.org>
To: Wei Wang <wei.w.wang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
virtio-dev@lists.oasis-open.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
virtualization <virtualization@lists.linux-foundation.org>,
KVM list <kvm@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Paolo Bonzini <pbonzini@redhat.com>,
liliang.opensource@gmail.com, yang.zhang.wz@gmail.com,
quan.xu0@gmail.com, nilal@redhat.com,
Rik van Riel <riel@redhat.com>,
peterx@redhat.com
Subject: Re: [PATCH v35 1/5] mm: support to get hints of free page blocks
Date: Wed, 11 Jul 2018 13:09:49 +0200 [thread overview]
Message-ID: <20180711110949.GJ20050@dhcp22.suse.cz> (raw)
In-Reply-To: <5B45E17D.2090205@intel.com>
On Wed 11-07-18 18:52:45, Wei Wang wrote:
> On 07/11/2018 05:21 PM, Michal Hocko wrote:
> > On Tue 10-07-18 18:44:34, Linus Torvalds wrote:
> > [...]
> > > That was what I tried to encourage with actually removing the pages
> > > form the page list. That would be an _incremental_ interface. You can
> > > remove MAX_ORDER-1 pages one by one (or a hundred at a time), and mark
> > > them free for ballooning that way. And if you still feel you have tons
> > > of free memory, just continue removing more pages from the free list.
> > We already have an interface for that. alloc_pages(GFP_NOWAIT, MAX_ORDER -1).
> > So why do we need any array based interface?
>
> Yes, I'm trying to get free pages directly via alloc_pages, so there will be
> no new mm APIs.
OK. The above was just a rough example. In fact you would need a more
complex gfp mask. I assume you only want to balloon only memory directly
usable by the kernel so it will be
(GFP_KERNEL | __GFP_NOWARN) & ~__GFP_RECLAIM
> I plan to let free page allocation stop when the remaining system free
> memory becomes close to min_free_kbytes (prevent swapping).
~__GFP_RECLAIM will make sure you are allocate as long as there is any
memory without reclaim. It will not even poke the kswapd to do the
background work. So I do not think you would need much more than that.
But let me note that I am not really convinced how this (or previous)
approach will really work in most workloads. We tend to cache heavily so
there is rarely any memory free.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-07-11 11:09 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-10 9:31 [PATCH v35 0/5] Virtio-balloon: support free page reporting Wei Wang
2018-07-10 9:31 ` [PATCH v35 1/5] mm: support to get hints of free page blocks Wei Wang
2018-07-10 10:16 ` Wang, Wei W
2018-07-10 17:33 ` Linus Torvalds
2018-07-11 1:28 ` Wei Wang
2018-07-11 1:44 ` Linus Torvalds
2018-07-11 9:21 ` Michal Hocko
2018-07-11 10:52 ` Wei Wang
2018-07-11 11:09 ` Michal Hocko [this message]
2018-07-11 13:55 ` Wang, Wei W
2018-07-11 14:38 ` Michal Hocko
2018-07-11 19:36 ` Michael S. Tsirkin
2018-07-11 16:23 ` Linus Torvalds
2018-07-12 2:21 ` Wei Wang
2018-07-12 2:30 ` Linus Torvalds
2018-07-12 2:52 ` Wei Wang
2018-07-12 8:13 ` Michal Hocko
2018-07-12 11:34 ` Wei Wang
2018-07-12 11:49 ` Michal Hocko
2018-07-13 0:33 ` Wei Wang
2018-07-12 13:12 ` Michal Hocko
2018-07-11 4:00 ` Michael S. Tsirkin
2018-07-11 4:04 ` Michael S. Tsirkin
2018-07-10 9:31 ` [PATCH v35 2/5] virtio-balloon: remove BUG() in init_vqs Wei Wang
2018-07-10 9:31 ` [PATCH v35 3/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Wei Wang
2018-07-10 9:31 ` [PATCH v35 4/5] mm/page_poison: expose page_poisoning_enabled to kernel modules Wei Wang
2018-07-10 9:31 ` [PATCH v35 5/5] virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON Wei Wang
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