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From: "Wang, Wei W" <wei.w.wang@intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
	Alexander Duyck <alexander.duyck@gmail.com>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>,
	kvm list <kvm@vger.kernel.org>,
	David Hildenbrand <david@redhat.com>,
	"Hansen, Dave" <dave.hansen@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	Yang Zhang <yang.zhang.wz@gmail.com>,
	"pagupta@redhat.com" <pagupta@redhat.com>,
	Rik van Riel <riel@surriel.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	"lcapitulino@redhat.com" <lcapitulino@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Williams, Dan J" <dan.j.williams@intel.com>,
	Alexander Duyck <alexander.h.duyck@linux.intel.com>
Subject: RE: use of shrinker in virtio balloon free page hinting
Date: Wed, 17 Jul 2019 15:46:57 +0000
Message-ID: <286AC319A985734F985F78AFA26841F73E16D4B2@shsmsx102.ccr.corp.intel.com> (raw)
In-Reply-To: <20190717071332-mutt-send-email-mst@kernel.org>

On Wednesday, July 17, 2019 7:21 PM, Michael S. Tsirkin wrote:
> 
> Wei, others,
> 
> ATM virtio_balloon_shrinker_scan will only get registered when deflate on
> oom feature bit is set.
> 
> Not sure whether that's intentional. 

Yes, we wanted to follow the old oom behavior, which allows the oom notifier
to deflate pages only when this feature bit has been negotiated.


> Assuming it is:
> 
> virtio_balloon_shrinker_scan will try to locate and free pages that are
> processed by host.
> The above seems broken in several ways:
> - count ignores the free page list completely

Do you mean virtio_balloon_shrinker_count()? It just reports to
do_shrink_slab the amount of freeable memory that balloon has.
(vb->num_pages and vb->num_free_page_blocks are all included )

> - if free pages are being reported, pages freed
>   by shrinker will just get re-allocated again

fill_balloon will re-try the allocation after sleeping 200ms once allocation fails.

 
> I was unable to make this part of code behave in any reasonable way - was
> shrinker usage tested? What's a good way to test that?

Please see the example that I tested before : https://lkml.org/lkml/2018/8/6/29
(just the first one: *1. V3 patches)

What problem did you see?

I just tried the latest code, and find ballooning reports a #GP (seems caused by
418a3ab1e). 
I'll take a look at the details in the office tomorrow.

Best,
Wei

  parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-17 11:20 Michael S. Tsirkin
2019-07-17 11:32 ` David Hildenbrand
2019-07-17 14:10 ` David Hildenbrand
2019-07-17 14:34   ` Michael S. Tsirkin
2019-07-17 14:38     ` David Hildenbrand
2019-07-17 15:46 ` Wang, Wei W [this message]
2019-07-18  4:13   ` Michael S. Tsirkin
2019-07-18  5:57     ` Wei Wang
2019-07-18  5:58       ` Michael S. Tsirkin
2019-07-18  6:30         ` Wei Wang
2019-07-18  6:47           ` Michael S. Tsirkin
2019-07-18  9:08             ` Wei Wang

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