linux-kernel - Re: [PATCH] x86,NUMA:Get the number of ram pages directly in numa_meminfo_cover

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Message-ID: <20230618070850.GY52412@kernel.org>
Date:   Sun, 18 Jun 2023 10:08:50 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Liam Ni <zhiguangni01@...il.com>
Cc:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        akpm@...ux-foundation.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] x86,NUMA:Get the number of ram pages directly in
 numa_meminfo_cover_memory()

On Sat, Jun 17, 2023 at 06:47:11PM +0800, Liam Ni wrote:
> On Fri, 16 Jun 2023 at 01:00, Mike Rapoport <rppt@...nel.org> wrote:
> >
> > On Fri, Jun 16, 2023 at 12:20:16AM +1000, Liam Ni wrote:
> > > In a previous implementation,The ram page is calculated
> > > by counting the number of holes,
> > > however,the number of ram pages is calculated during hole calculation.
> > > Therefore,we can directly calculate the amount of ram pages.
> > >
> > > Signed-off-by: Liam Ni <zhiguangni01@...il.com>
> > > ---
> > >  arch/x86/mm/numa.c |  4 ++--
> > >  include/linux/mm.h |  4 ++++
> > >  mm/mm_init.c       | 33 +++++++++++++++++++++++++++++++++
> > >  3 files changed, 39 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > > index 2aadb2019b4f..8ea0e956e3d7 100644
> > > --- a/arch/x86/mm/numa.c
> > > +++ b/arch/x86/mm/numa.c
> > > @@ -461,12 +461,12 @@ static bool __init numa_meminfo_cover_memory(const struct numa_meminfo *mi)
> > >               u64 s = mi->blk[i].start >> PAGE_SHIFT;
> > >               u64 e = mi->blk[i].end >> PAGE_SHIFT;
> > >               numaram += e - s;
> > > -             numaram -= __absent_pages_in_range(mi->blk[i].nid, s, e);
> > > +             numaram += __available_pages_in_range(mi->blk[i].nid, s, e);
> >
> > This is wrong. You add number of pages in range core MM sees to the number
> > of pages covered by the numa_meminfo.
> >
> > More generally, rather than traverse all the numa_meminfo's and for each of
> > them traverse all the regions in memblock.memory it's enough to count
> > memory in memblock that doesn't have the node assigned and compare it to
> > memblock_phys_mem_size().
> 
> Logic like below?
> static bool __init numa_meminfo_cover_memory(const struct numa_meminfo *mi)
> {
>    u64 error_value;
>    error_value = pages_without_nid_in_range(0,max_pfn);
>     if ((error_value ) >= (1 << (20 - PAGE_SHIFT))) {
>         //print error information
>         return false;
>      }
>      return true;
> }
> 
> I can't figure out why compare it with memblock_phys_mem_size().
> The number of pages in memblock that doesn't have the node
> assigned,which also means that these pages are not in numa_info.
> So these pages can represent the number of lose pages.

Yes, there is no need to compare with memblock_phys_mem_size() if you count
pages that don't have nid set in memblock.
 
> Thanks
> Liam Ni

-- 
Sincerely yours,
Mike.