linux-kernel - Re: [PATCH] proc: mm: export PTE sizes directly in smaps (v3)

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Date:   Thu, 1 Dec 2016 16:50:39 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Dave Hansen <dave@...1.net>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        khandual@...ux.vnet.ibm.com, vbabka@...e.cz, linux-mm@...ck.org,
        Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] proc: mm: export PTE sizes directly in smaps (v3)

On Tue, Nov 29, 2016 at 10:17 PM, Dave Hansen <dave@...1.net> wrote:
>
> Andrew, you can drop proc-mm-export-pte-sizes-directly-in-smaps-v2.patch,
> and replace it with this.

You added a warning and it immediately appears:


[    0.402603] ------------[ cut here ]------------
[    0.402844] WARNING: CPU: 0 PID: 1 at
/home/andy/prj/linux-netboot/mm/hugetlb.c:2918
hugetlb_add_hstate+0x143/0
x14b
[    0.403042] Modules linked in:
[    0.403233] CPU: 0 PID: 1 Comm: swapper Not tainted
4.9.0-rc7-next-20161201+ #1
[    0.403499] Call Trace:
[    0.403677]  dump_stack+0x16/0x1d
[    0.404081]  __warn+0xd1/0xf0
[    0.404289]  ? hugetlb_add_hstate+0x143/0x14b
[    0.404491]  warn_slowpath_null+0x25/0x30
[    0.404695]  hugetlb_add_hstate+0x143/0x14b
[    0.404908]  hugetlb_init+0x79/0x3af
[    0.405249]  ? wake_up_process+0xf/0x20
[    0.405450]  ? kcompactd_run+0x50/0x90
[    0.405638]  ? compact_zone+0x7c0/0x7c0
[    0.405842]  ? hugetlb_add_hstate+0x14b/0x14b
[    0.406082]  do_one_initcall+0x2f/0x160
[    0.406286]  ? repair_env_string+0x12/0x54
[    0.406482]  ? parse_args+0x2a1/0x5a0
[    0.406684]  ? __dquot_free_space+0xa0/0x2d0
[    0.406892]  ? kernel_init_freeable+0xe4/0x18a
[    0.407088]  kernel_init_freeable+0x107/0x18a
[    0.407303]  ? rest_init+0x60/0x60
[    0.407496]  kernel_init+0xb/0x100
[    0.407703]  ? schedule_tail_wrapper+0x9/0x10
[    0.408099]  ret_from_fork+0x19/0x30
[    0.408302] ---[ end trace 601ba77b9b62b9d7 ]---
[    0.408481] HugeTLB registered 4 MB page size, pre-allocated 0 pages


Quark SoC here.

Besides that see below.

> +/*
> + * What units should we use for a given number?  We want
> + * 2048 to be 2k, so we return 'k'.  1048576 should be
> + * 1M, so we return 'M'.
> + */
> +static char size_unit(unsigned long long nr)
> +{
> +       /*
> +        * This ' ' might look a bit goofy in the output.  But, why
> +        * bother doing anything.  Do we even have a <1k page size?
> +        */
> +       if (nr < (1ULL<<10))
> +               return ' ';
> +       if (nr < (1ULL<<20))
> +               return 'k';
> +       if (nr < (1ULL<<30))
> +               return 'M';
> +       if (nr < (1ULL<<40))
> +               return 'G';
> +       if (nr < (1ULL<<50))
> +               return 'T';
> +       if (nr < (1ULL<<60))
> +               return 'P';
> +       return 'E';
> +}
> +
> +/*
> + * How should we shift down a a given number to scale it
> + * with the units we are printing it as? 2048 to be 2k,
> + * so we want it shifted down by 10.  1048576 should be
> + * 1M, so we want it shifted down by 20.
> + */
> +static int size_shift(unsigned long long nr)
> +{
> +       if (nr < (1ULL<<10))
> +               return 0;
> +       if (nr < (1ULL<<20))
> +               return 10;
> +       if (nr < (1ULL<<30))
> +               return 20;
> +       if (nr < (1ULL<<40))
> +               return 30;
> +       if (nr < (1ULL<<50))
> +               return 40;
> +       if (nr < (1ULL<<60))
> +               return 50;
> +       return 60;
> +}
> +

New copy of string_get_size() ?

Something similar was discussed for EFI stuff like half a year ago?

> +static void show_one_smap_pte(struct seq_file *m, unsigned long bytes_rss,
> +               unsigned long pte_size)
> +{
> +       seq_printf(m, "Ptes@...%cB:     %8lu kB\n",
> +                       pte_size >> size_shift(pte_size),
> +                       size_unit(pte_size),
> +                       bytes_rss >> 10);
> +}


> +       /*
> +        * PGD_SIZE isn't widely made available by architecures,
> +        * so use PUD_SIZE*PTRS_PER_PUD as a substitute.
> +        *
> +        * Check for sizes that might be mapped by a PGD.  There
> +        * are none of these known today, but be on the lookout.
> +        * If this trips, we will need to update the mss->rss_*
> +        * code in fs/proc/task_mmu.c.
> +        */
> +       WARN_ON_ONCE((PAGE_SIZE << order) >= PUD_SIZE * PTRS_PER_PUD);

This what I got.

-- 
With Best Regards,
Andy Shevchenko