From: Yosry Ahmed <yosryahmed@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Sean Christopherson <seanjc@google.com>,
Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>,
Zefan Li <lizefan.x@bytedance.com>, Marc Zyngier <maz@kernel.org>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeelb@google.com>,
Oliver Upton <oupton@google.com>,
Shaoqin <shaoqin.huang@intel.com>,
Cgroups <cgroups@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH v6 1/4] mm: add NR_SECONDARY_PAGETABLE to count secondary page table uses.
Date: Mon, 15 Aug 2022 02:18:20 -0700 [thread overview]
Message-ID: <CAJD7tkY5SfdhC7-4B7QuJGUVj_Ts+xwCP5FUZ-Lvg=fd1p_xAQ@mail.gmail.com> (raw)
In-Reply-To: <CAJD7tkbc+E7f+ENRazf0SO7C3gR2bHiN4B0F1oPn8Pa6juAVfg@mail.gmail.com>
On Mon, Aug 8, 2022 at 1:06 PM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Mon, Jul 18, 2022 at 11:26 AM Yosry Ahmed <yosryahmed@google.com> wrote:
> >
> > On Tue, Jul 12, 2022 at 4:06 PM Sean Christopherson <seanjc@google.com> wrote:
> > >
> > > On Tue, Jul 12, 2022, Yosry Ahmed wrote:
> > > > Thanks for taking another look at this!
> > > >
> > > > On Thu, Jul 7, 2022 at 1:59 PM Sean Christopherson <seanjc@google.com> wrote:
> > > > >
> > > > > On Tue, Jun 28, 2022, Yosry Ahmed wrote:
> > > > > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > > > > > index aab70355d64f3..13190d298c986 100644
> > > > > > --- a/include/linux/mmzone.h
> > > > > > +++ b/include/linux/mmzone.h
> > > > > > @@ -216,6 +216,7 @@ enum node_stat_item {
> > > > > > NR_KERNEL_SCS_KB, /* measured in KiB */
> > > > > > #endif
> > > > > > NR_PAGETABLE, /* used for pagetables */
> > > > > > + NR_SECONDARY_PAGETABLE, /* secondary pagetables, e.g. kvm shadow pagetables */
> > > > >
> > > > > Nit, s/kvm/KVM, and drop the "shadow", which might be misinterpreted as saying KVM
> > > > > pagetables are only accounted when KVM is using shadow paging. KVM's usage of "shadow"
> > > > > is messy, so I totally understand why you included it, but in this case it's unnecessary
> > > > > and potentially confusing.
> > > > >
> > > > > And finally, something that's not a nit. Should this be wrapped with CONFIG_KVM
> > > > > (using IS_ENABLED() because KVM can be built as a module)? That could be removed
> > > > > if another non-KVM secondary MMU user comes along, but until then, #ifdeffery for
> > > > > stats the depend on a single feature seems to be the status quo for this code.
> > > > >
> > > >
> > > > I will #ifdef the stat, but I will emphasize in the docs that is
> > > > currently *only* used for KVM so that it makes sense if users without
> > > > KVM don't see the stat at all. I will also remove the stat from
> > > > show_free_areas() in mm/page_alloc.c as it seems like none of the
> > > > #ifdefed stats show up there.
> > >
> > > It's might be worth getting someone from mm/ to weigh in before going through the
> > > trouble, my suggestion/question is based purely on the existing code.
> >
> > Any mm folks with an opinion about this?
> >
> > Any preference on whether we should wrap NR_SECONDARY_PAGETABLE stats
> > with #ifdef CONFIG_KVM for now as it is currently the only source for
> > this stat?
>
> Any input here?
>
> Johannes, you have been involved in discussions in earlier versions of
> this series, any thoughts here?
Andrew, do you have an opinion on this? If not, I will send a v7 with
the nits discussed with Sean. I think otherwise this series has
sufficient ACKs.
Would this be merged through the mm tree or kvm tree? This was based
on the kvm/queue branch but I think I can rebase it on top of
mm-unstable, I think all dependencies that this would have added in
kvm/queue would have been fanned to mm by now.
next prev parent reply other threads:[~2022-08-15 9:19 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-28 22:09 [PATCH v6 0/4] KVM: mm: count KVM mmu usage in memory stats Yosry Ahmed
2022-06-28 22:09 ` [PATCH v6 1/4] mm: add NR_SECONDARY_PAGETABLE to count secondary page table uses Yosry Ahmed
2022-06-29 10:29 ` Marc Zyngier
2022-07-07 20:59 ` Sean Christopherson
2022-07-12 23:03 ` Yosry Ahmed
2022-07-12 23:05 ` Sean Christopherson
2022-07-18 18:26 ` Yosry Ahmed
2022-08-08 20:06 ` Yosry Ahmed
2022-08-15 9:18 ` Yosry Ahmed [this message]
2022-08-15 15:13 ` Johannes Weiner
2022-08-15 15:39 ` Yosry Ahmed
2022-08-17 17:25 ` Andrew Morton
2022-08-17 17:24 ` Andrew Morton
2022-08-17 22:27 ` Yosry Ahmed
2022-08-23 0:04 ` Yosry Ahmed
2022-08-23 0:08 ` Andrew Morton
2022-06-28 22:09 ` [PATCH v6 2/4] KVM: mmu: add a helper to account memory used by KVM MMU Yosry Ahmed
2022-06-29 10:30 ` Marc Zyngier
2022-07-07 21:08 ` Sean Christopherson
2022-07-12 23:03 ` Yosry Ahmed
2022-06-28 22:09 ` [PATCH v6 3/4] KVM: x86/mmu: count KVM mmu usage in secondary pagetable stats Yosry Ahmed
2022-07-07 21:11 ` Sean Christopherson
2022-06-28 22:09 ` [PATCH v6 4/4] KVM: arm64/mmu: count KVM s2 " Yosry Ahmed
2022-06-29 10:30 ` Marc Zyngier
2022-06-30 21:01 ` [PATCH v6 0/4] KVM: mm: count KVM mmu usage in memory stats Yosry Ahmed
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