linux-kernel - RE: use of shrinker in virtio balloon free page hinting

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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

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