Date: Wed, 25 Jun 2014 12:18:43 -0500 From: Alan Cox <alc@rice.edu> To: Julian Elischer <julian@freebsd.org>, Alfred Perlstein <alfred@freebsd.org>, attilio@FreeBSD.org, Gleb Smirnoff <glebius@freebsd.org> Cc: Alan Cox <alc@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, =?UTF-8?B?Um9nZXIgUGF1IE1vbm7DqQ==?= <royger@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r267858 - in head/sys/dev: virtio/balloon xen/balloon Message-ID: <53AB0473.8080709@rice.edu> In-Reply-To: <53AB02FD.20502@freebsd.org> References: <201406250951.s5P9p8YR017159@svn.freebsd.org> <CAJ-FndD4M8QkejyTv4R_9qoThqvFinYbHP4YSby6mQS9EKSYPA@mail.gmail.com> <20140625120932.GM28199@FreeBSD.org> <CAJ-FndAHV1sHOreWThZoVr-bbQSXv9=QPHX9=QZNQmkGFUTRMw@mail.gmail.com> <53AAE7D0.2090508@freebsd.org> <53AB02FD.20502@freebsd.org>
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On 06/25/2014 12:12, Julian Elischer wrote: > On 6/25/14, 11:16 PM, Alfred Perlstein wrote: >> On 6/25/14 5:41 AM, Attilio Rao wrote: >>> On Wed, Jun 25, 2014 at 2:09 PM, Gleb Smirnoff <glebius@freebsd.org> >>> wrote: >>>> On Wed, Jun 25, 2014 at 01:58:29PM +0200, Attilio Rao wrote: >>>> A> > Log: >>>> A> > xen/virtio: fix balloon drivers to not mark pages as WIRED >>>> A> > >>>> A> > Prevent the Xen and VirtIO balloon drivers from marking >>>> pages as >>>> A> > wired. This prevents them from increasing the system wired >>>> page count, >>>> A> > which can lead to mlock failing because of hitting the limit in >>>> A> > vm.max_wired. >>>> A> >>>> A> This change is conceptually wrong. >>>> A> The pages balloon is allocating are unmanaged and they should be >>>> wired >>>> A> by definition. Alan and I are considering enforcing this (mandatory >>>> A> wired pages for unmanaged pages allocation) directly in the KPI. >>>> A> This in practice just seem an artifact to deal with scarce wired >>>> A> memory limit. I suggest that for the XEN case this limit gets >>>> bumped >>>> A> rather relying on similar type of hacks. >>>> >>>> Proper limit would be to count pages wired by userland via mlock(2) >>>> and enforce limit only on those pages. Pages wired by kernel should >>>> be either unlimited or controled by a separate limit. >>> FWIW, I mostly agree with this. I think that the kernel and userland >>> limits should be split apart. But for the time being, rising the limit >>> is better. >>> >>> Attilio >>> >>> >> Can you explain? I would think that if you were designing some kind >> of embedded device you would want to know exactly how much locked >> pages there are overall, not just in userland. >> >> Meaning you would not want to overcommit and have too many locked >> pages due to kernel+user. >> >> Perhaps that needs an API as well? > > these pages are the VM equivalent of memory pages that were 'found to > be flaky and taken out of service" > I think "wired" is a bad description for those. > > > That doesn't matter. To the rest of the VM system, and, in particular, the page daemon, one category is indistinguishable from the other.home | help
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