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Message-ID: <CA+2MQi_ajOZge-_1S0pAt+o-beT6QQru9ogYBcwzAs+tWqrPcQ@mail.gmail.com>
Date: Wed, 23 Dec 2020 11:42:12 +0800
From: Liang Li <liliang324@...il.com>
To: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Alexander Duyck <alexander.duyck@...il.com>,
Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
Mel Gorman <mgorman@...hsingularity.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Dan Williams <dan.j.williams@...el.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
David Hildenbrand <david@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Dave Hansen <dave.hansen@...el.com>,
Michal Hocko <mhocko@...e.com>,
Liang Li <liliangleo@...iglobal.com>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
virtualization@...ts.linux-foundation.org, qemu-devel@...gnu.org
Subject: Re: [RFC PATCH 1/3] mm: support hugetlb free page reporting
> On 12/22/20 11:59 AM, Alexander Duyck wrote:
> > On Mon, Dec 21, 2020 at 11:47 PM Liang Li <liliang.opensource@...il.com> wrote:
> >> +
> >> + if (huge_page_order(h) > MAX_ORDER)
> >> + budget = HUGEPAGE_REPORTING_CAPACITY;
> >> + else
> >> + budget = HUGEPAGE_REPORTING_CAPACITY * 32;
> >
> > Wouldn't huge_page_order always be more than MAX_ORDER? Seems like we
> > don't even really need budget since this should probably be pulling
> > out no more than one hugepage at a time.
>
> On standard x86_64 configs, 2MB huge pages are of order 9 < MAX_ORDER (11).
> What is important for hugetlb is the largest order that can be allocated
> from buddy. Anything bigger is considered a gigantic page and has to be
> allocated differently.
>
> If the code above is trying to distinguish between huge and gigantic pages,
> it is off by 1. The largest order that can be allocated from the buddy is
> (MAX_ORDER - 1). So, the check should be '>='.
>
> --
> Mike Kravetz
Yes, you're right! thanks
Liang
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