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From: Michal Hocko <mhocko@kernel.org>
To: "Niklas Hambüchen" <mail@nh2.me>
Cc: linux-mm@kvack.org
Subject: Re: Question about the laziness of MADV_FREE
Date: Thu, 29 Nov 2018 21:54:23 +0100	[thread overview]
Message-ID: <20181129205423.GA6923@dhcp22.suse.cz> (raw)
In-Reply-To: <1423043c-af4b-0288-9f42-e00be320491b@nh2.me>

On Thu 29-11-18 20:21:49, Niklas Hamb�chen wrote:
> Hello Michal,
> 
> thanks for the swift reply and patch!
> 
> > We batch multiple pages to become really lazyfree. This means that those
> > pages are sitting on a per-cpu list (see mark_page_lazyfree). So the
> > the number drift depends on the number of CPUs.
> 
> Is there an upper bound that I can rely on in order to judge how far off the accounting is (perhaps depending on the number of CPUs as you say)?
> For example, if the drift is bounded to, say 10%, that would probably be fine, while if it could be off by 2x or so, that would make system inspection tough.

>From a quick look it should be 15*number_of_cpus unless I have missed
other caching. So this shouldn't be all that much unless you have a
giant machine with hundreds of cpus.
-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2018-11-29 20:54 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-29 17:46 Niklas Hambüchen
2018-11-29 18:00 ` Michal Hocko
2018-11-29 19:21   ` Niklas Hambüchen
2018-11-29 20:54     ` Michal Hocko [this message]
2018-11-29 23:00       ` Niklas Hambüchen
2018-11-30  8:19         ` Michal Hocko

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