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Date:   Fri, 24 Nov 2023 15:31:16 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org
Subject: Re: [PATCH] mm/page.c: move mem_init_print_info() to later place
Message-ID: <ZWBRRK9C9MnvtEzW@MiWiFi-R3L-srv>
References: <20231122043550.489889-1-bhe@redhat.com>
 <20231122150817.GA634321@kernel.org>
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On 11/22/23 at 05:08pm, Mike Rapoport wrote:
> Hi Baoquan,
> 
> 
> On Wed, Nov 22, 2023 at 12:35:50PM +0800, Baoquan He wrote:
> 
> > Subject: [PATCH] mm/page.c: move mem_init_print_info() to later place
> 
> We don't have mm/page.c, 

Thanks for reviewing.

Yes, this was queued in my local branch long time ago, I forgot to
update the file name.

> 
> > Currently if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, only part of
> > pages are initialized and added into buddy allocator at early stage. Then
> > the system memory information printed by mem_init_print_info() is
> > incorrect. The snippets of boot log are pasted here:
> > -----------------------------------------------------------------------
> > [    0.059606] mem auto-init: stack:all(zero), heap alloc:off, heap free:off
> > [    0.059622] software IO TLB: area num 64.
> > [    0.143887] Memory: 1767888K/133954872K available (20480K kernel code, 3284K rwdata, 8972K rodata, 4572K init, 4916K bss, 2529756K reserved, 0K cma-reserved)
> > [    0.145111] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=64, Nodes=2
> > ---------------------------------------------------------------------------
> 
> At this point only the pages that were initialized and free are available.
> The message does not reflect that large part of memory is still not initialized,
> but it's not wrong.

Agree. I noticed this because I often need check the memory init and
memory size during kernel bootup. The current message gives people a
shock at first glance because it looks like a huge reserved memory
existing in system.

> 
> > Here, move mem_init_print_info() to later place until page init is
> > finished. After the fix, the printed memory information is like this:
> > -------------------------------------------------------------------------
> > [  +0.001002] smpboot: Total of 64 processors activated (293724.92 BogoMIPS)
> > [  +0.050086] node 0 deferred pages initialised in 45ms
> > [  +0.007309] node 1 deferred pages initialised in 53ms
> > [    4.035449] Memory: 131272772K/133954872K available (20480K kernel code, 3284K rwdata, 8972K rodata, 4572K init, 4916K bss, 2529700K reserved, 0K cma-reserved)
> > [  +0.015995] devtmpfs: initialized
> > [  +0.003943] x86/mm: Memory block size: 2048MB
> > -------------------------------------------------------------------------
> 
> If we print this message that late, some of the memory will be allocated
> from buddy and it maybe confusing.

that's true.

> 
> I suggest to print how much memory is not yet initialized and leave
> mem_init_print_info() where it is now.

Sounds great to me, will work out a new version as suggested.

>  
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  include/linux/gfp.h | 1 +
> >  init/main.c         | 1 +
> >  mm/mm_init.c        | 3 +--
> >  3 files changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index de292a007138..2d69fa59b489 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -335,6 +335,7 @@ void drain_local_pages(struct zone *zone);
> >  
> >  void page_alloc_init_late(void);
> >  void setup_pcp_cacheinfo(void);
> > +void mem_init_print_info(void);
> >  
> >  /*
> >   * gfp_allowed_mask is set to GFP_BOOT_MASK during early boot to restrict what
> > diff --git a/init/main.c b/init/main.c
> > index e24b0780fdff..88f238a478a1 100644
> > --- a/init/main.c
> > +++ b/init/main.c
> > @@ -1547,6 +1547,7 @@ static noinline void __init kernel_init_freeable(void)
> >  	workqueue_init_topology();
> >  	padata_init();
> >  	page_alloc_init_late();
> > +	mem_init_print_info();
>   
> No need to make mem_init_print_info() global and call it from main.c, you
> can call it from page_alloc_init_late().

Agree, that's much better if we take that way.

> 
> >  	do_basic_setup();
> >  
> > diff --git a/mm/mm_init.c b/mm/mm_init.c
> > index 077bfe393b5e..d08f7c7f75f1 100644
> > --- a/mm/mm_init.c
> > +++ b/mm/mm_init.c
> > @@ -2703,7 +2703,7 @@ static void __init report_meminit(void)
> >  		pr_info("mem auto-init: clearing system memory may take some time...\n");
> >  }
> >  
> > -static void __init mem_init_print_info(void)
> > +void __init mem_init_print_info(void)
> >  {
> >  	unsigned long physpages, codesize, datasize, rosize, bss_size;
> >  	unsigned long init_code_size, init_data_size;
> > @@ -2774,7 +2774,6 @@ void __init mm_core_init(void)
> >  	kmsan_init_shadow();
> >  	stack_depot_early_init();
> >  	mem_init();
> > -	mem_init_print_info();
> >  	kmem_cache_init();
> >  	/*
> >  	 * page_owner must be initialized after buddy is ready, and also after
> > -- 
> > 2.41.0
> > 
> 
> -- 
> Sincerely yours,
> Mike.
>