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Date: Mon, 1 Feb 2021 15:27:33 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Yafang Shao <laoar.shao@...il.com>
Cc: david@...hat.com, vbabka@...e.cz, linmiaohe@...wei.com,
cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
pmladek@...e.com, rostedt@...dmis.org,
sergey.senozhatsky@...il.com, linux@...musvillemoes.dk,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v2 3/3] vsprintf: dump full information of page flags in
pGp
On Mon, Feb 01, 2021 at 07:56:10PM +0800, Yafang Shao wrote:
> Currently the pGp only shows the names of page flags, rather than
> the full information including section, node, zone, last cpupid and
> kasan tag. While it is not easy to parse these information manually
> because there're so many flavors. Let's interpret them in pGp as well.
>
> - Before the patch,
> [ 6343.396602] Slab 0x000000004382e02b objects=33 used=3 fp=0x000000009ae06ffc flags=0x17ffffc0010200(slab|head)
>
> - After the patch,
> [ 6871.296131] Slab 0x00000000c0e19a37 objects=33 used=3 fp=0x00000000c4902159 flags=0x17ffffc0010200(Node 0,Zone 2,Lastcpupid 0x1fffff,slab|head)
>
> The Documentation and test cases are also updated.
Thanks for an update, my comments below.
...
> - %pGp referenced|uptodate|lru|active|private
> + %pGp Node 0,Zone 2,referenced|uptodate|lru|active|private
Since of the nature of printf() buffer, I wonder if these should be at the end.
I.o.w. the question is is the added material more important to user to see than
the existed one?
...
> +static void __init
> +page_flags_test(int section, int node, int zone, int last_cpupid,
> + int kasan_tag, int flags, const char *name, char *cmp_buf)
> +{
> + unsigned long page_flags = 0;
> + unsigned long size = 0;
> +
> +#ifdef SECTION_IN_PAGE_FLAGS
> + page_flags |= (sec & SECTIONS_MASK) << SECTIONS_PGSHIFT;
> + snprintf(cmp_buf, BUF_SIZE, "Section %#x,", sec);
I would keep it in the same form as latter ones, i.e.
snprintf(cmp_buf + size, BUF_SIZE - size, "Section %#x,", sec);
In this case it will be easier if at some point we might need to reshuffle.
> + size = strlen(cmp_buf);
> +#endif
> +
> + page_flags |= (node & NODES_MASK) << NODES_PGSHIFT;
> + snprintf(cmp_buf + size, BUF_SIZE - size, "Node %d", node);
> + size = strlen(cmp_buf);
> +
> + page_flags |= (zone & ZONES_MASK) << ZONES_PGSHIFT;
> + snprintf(cmp_buf + size, BUF_SIZE - size, ",Zone %d", zone);
> + size = strlen(cmp_buf);
> +
> +#ifndef LAST_CPUPID_NOT_IN_PAGE_FLAGS
> + page_flags |= (last_cpupid & LAST_CPUPID_MASK) << LAST_CPUPID_PGSHIFT;
> + snprintf(cmp_buf + size, BUF_SIZE - size, ",Lastcpupid %#x", last_cpupid);
> + size = strlen(cmp_buf);
> +#endif
> +
> +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
> + page_flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT;
> + snprintf(cmp_buf + size, BUF_SIZE - size, ",Kasantag %#x", tag);
> + size = strlen(cmp_buf);
> +#endif
> +
> + test(cmp_buf, "%pGp", &page_flags);
> +
> + if (flags) {
If below will be always for flags set, I would rewrite this condition as
if (!flags)
return;
but it's up to you.
> + page_flags |= flags;
> + snprintf(cmp_buf + size, BUF_SIZE - size, ",%s", name);
> + test(cmp_buf, "%pGp", &page_flags);
> + }
> +}
...
> - flags = 0;
> - flags |= 1UL << PG_uptodate | 1UL << PG_dirty | 1UL << PG_lru
> - | 1UL << PG_active | 1UL << PG_swapbacked;
I would leave this untouched and reuse below...
> + cmp_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);
> + if (!cmp_buffer)
> + return;
...as
> + page_flags_test(0, 0, 0, 0, 0, 0, NULL, cmp_buffer);
flags = 0;
page_flags_test(0, 0, 0, 0, 0, flags, NULL, cmp_buffer);
> + page_flags_test(1, 1, 1, 0x1ffff, 1,
> + (1UL << PG_uptodate | 1UL << PG_dirty | 1UL << PG_lru
> + | 1UL << PG_active | 1UL << PG_swapbacked),
> + "uptodate|dirty|lru|active|swapbacked",
> + cmp_buffer);
flags |= 1UL << PG_uptodate | 1UL << PG_dirty | 1UL << PG_lru
| 1UL << PG_active | 1UL << PG_swapbacked;
page_flags_test(1, 1, 1, 0x1ffff, 1, flags,
"uptodate|dirty|lru|active|swapbacked",
cmp_buffer);
...
> +static const struct page_flags_layout pfl[] = {
> + {SECTIONS_WIDTH, SECTIONS_PGSHIFT, SECTIONS_MASK,
> + &default_dec_spec, "Section "},
> + {NODES_WIDTH, NODES_PGSHIFT, NODES_MASK,
> + &default_dec_spec, "Node "},
> + {ZONES_WIDTH, ZONES_PGSHIFT, ZONES_MASK,
> + &default_dec_spec, "Zone "},
> + {LAST_CPUPID_WIDTH, LAST_CPUPID_PGSHIFT, LAST_CPUPID_MASK,
> + &default_flag_spec, "Lastcpupid "},
> + {KASAN_TAG_WIDTH, KASAN_TAG_PGSHIFT, KASAN_TAG_MASK,
> + &default_flag_spec, "Kasantag "},
> +};
Please add trailing space only once where it's needed (below in the code).
...
> +static
> +char *format_page_flags(char *buf, char *end, unsigned long page_flags)
> +{
> + unsigned long flags = page_flags & ((1UL << NR_PAGEFLAGS) - 1);
> + int size = ARRAY_SIZE(pfl);
> + bool separator = false;
> + int i;
> +
> + for (i = 0; i < size; i++) {
> + if (pfl[i].width == 0)
> + continue;
> +
> + if (separator) {
> + if (buf < end)
> + *buf = ',';
> + buf++;
> + }
> +
> +
One blank line is enough.
> + buf = string(buf, end, pfl[i].name, *pfl[i].spec);
> +
> + buf = number(buf, end, (page_flags >> pfl[i].shift) & pfl[i].mask,
> + *pfl[i].spec);
> + separator = true;
> + }
> +
> + if (flags) {
> + if (buf < end)
> + *buf = ',';
> + buf++;
> + }
I think you may optimize above to avoid using the separator variable.
DECLARE_BITMAP(mask, ARRAY_SIZE(pfl));
unsigned long flags;
unsigned long last;
for (i = 0; i < ARRAY_SIZE(pfl); i++)
__assign_bit(mask, pfl[i].width);
last = find_last_bit(mask, ARRAY_SIZE(pfl));
for_each_set_bit(i, mask, ARRAY_SIZE(pfl)) {
flags = (page_flags >> pfl[i].shift) & pfl[i].mask;
/* Format: Flag Name + ' ' (space) + Number + ',' (separator) */
buf = string(buf, end, pfl[i].name, *pfl[i].spec);
if (buf < end)
*buf = ' ';
buf++;
buf = number(buf, end, flags, *pfl[i].spec);
/* No separator for the last entry */
if ((page_flags & (BIT(NR_PAGEFLAGS) - 1)) || (i != last)) {
if (buf < end)
*buf = ',';
buf++;
}
}
> + return buf;
> +}
--
With Best Regards,
Andy Shevchenko
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