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Date: Wed, 29 Aug 2018 11:16:30 -0400
From: Masayoshi Mizuma <msys.mizuma@...il.com>
To: Pavel.Tatashin@...rosoft.com, linux-mm@...ck.org,
n-horiguchi@...jp.nec.com, mhocko@...nel.org
Cc: linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 2/2] mm: zero remaining unavailable struct pages
Hi Horiguchi-san and Pavel
Thank you for your comments!
The Pavel's additional patch looks good to me, so I will add it to this series.
However, unfortunately, the movable_node option has something wrong yet...
When I offline the memory which belongs to movable zone, I got the following
warning. I'm trying to debug it.
I try to describe the issue as following.
If you have any comments, please let me know.
WARNING: CPU: 156 PID: 25611 at mm/page_alloc.c:7730 has_unmovable_pages+0x1bf/0x200
RIP: 0010:has_unmovable_pages+0x1bf/0x200
...
Call Trace:
is_mem_section_removable+0xd3/0x160
show_mem_removable+0x8e/0xb0
dev_attr_show+0x1c/0x50
sysfs_kf_seq_show+0xb3/0x110
seq_read+0xee/0x480
__vfs_read+0x36/0x190
vfs_read+0x89/0x130
ksys_read+0x52/0xc0
do_syscall_64+0x5b/0x180
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fe7b7823f70
...
I added a printk to catch the unmovable page.
---
@@ -7713,8 +7719,12 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
* is set to both of a memory hole page and a _used_ kernel
* page at boot.
*/
- if (found > count)
+ if (found > count) {
+ pr_info("DEBUG: %s zone: %lx page: %lx pfn: %lx flags: %lx found: %ld count: %ld \n",
+ __func__, zone, page, page_to_pfn(page), page->flags, found, count);
goto unmovable;
+ }
---
Then I got the following. The page (PFN: 0x1c0ff130d) flag is
0xdfffffc0040048 (uptodate|active|swapbacked)
---
DEBUG: has_unmovable_pages zone: 0xffff8c0ffff80380 page: 0xffffea703fc4c340 pfn: 0x1c0ff130d flags: 0xdfffffc0040048 found: 1 count: 0
---
And I got the owner from /sys/kernel/debug/page_owner.
Page allocated via order 0, mask 0x6280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO)
PFN 7532909325 type Movable Block 14712713 type Movable Flags 0xdfffffc0040048(uptodate|active|swapbacked)
__alloc_pages_nodemask+0xfc/0x270
alloc_pages_vma+0x7c/0x1e0
handle_pte_fault+0x399/0xe50
__handle_mm_fault+0x38e/0x520
handle_mm_fault+0xdc/0x210
__do_page_fault+0x243/0x4c0
do_page_fault+0x31/0x130
page_fault+0x1e/0x30
The page is allocated as anonymous page via page fault.
I'm not sure, but lru flag should be added to the page...?
Thanks,
Masa
On 08/27/2018 07:33 PM, Pasha Tatashin wrote:
> On 8/23/18 2:25 PM, Masayoshi Mizuma wrote:
>> From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
>>
>> There is a kernel panic that is triggered when reading /proc/kpageflags
>> on the kernel booted with kernel parameter 'memmap=nn[KMG]!ss[KMG]':
>>
>> BUG: unable to handle kernel paging request at fffffffffffffffe
>> PGD 9b20e067 P4D 9b20e067 PUD 9b210067 PMD 0
>> Oops: 0000 [#1] SMP PTI
>> CPU: 2 PID: 1728 Comm: page-types Not tainted 4.17.0-rc6-mm1-v4.17-rc6-180605-0816-00236-g2dfb086ef02c+ #160
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.fc28 04/01/2014
>> RIP: 0010:stable_page_flags+0x27/0x3c0
>> Code: 00 00 00 0f 1f 44 00 00 48 85 ff 0f 84 a0 03 00 00 41 54 55 49 89 fc 53 48 8b 57 08 48 8b 2f 48 8d 42 ff 83 e2 01 48 0f 44 c7 <48> 8b 00 f6 c4 01 0f 84 10 03 00 00 31 db 49 8b 54 24 08 4c 89 e7
>> RSP: 0018:ffffbbd44111fde0 EFLAGS: 00010202
>> RAX: fffffffffffffffe RBX: 00007fffffffeff9 RCX: 0000000000000000
>> RDX: 0000000000000001 RSI: 0000000000000202 RDI: ffffed1182fff5c0
>> RBP: ffffffffffffffff R08: 0000000000000001 R09: 0000000000000001
>> R10: ffffbbd44111fed8 R11: 0000000000000000 R12: ffffed1182fff5c0
>> R13: 00000000000bffd7 R14: 0000000002fff5c0 R15: ffffbbd44111ff10
>> FS: 00007efc4335a500(0000) GS:ffff93a5bfc00000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: fffffffffffffffe CR3: 00000000b2a58000 CR4: 00000000001406e0
>> Call Trace:
>> kpageflags_read+0xc7/0x120
>> proc_reg_read+0x3c/0x60
>> __vfs_read+0x36/0x170
>> vfs_read+0x89/0x130
>> ksys_pread64+0x71/0x90
>> do_syscall_64+0x5b/0x160
>> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> RIP: 0033:0x7efc42e75e23
>> Code: 09 00 ba 9f 01 00 00 e8 ab 81 f4 ff 66 2e 0f 1f 84 00 00 00 00 00 90 83 3d 29 0a 2d 00 00 75 13 49 89 ca b8 11 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 db d3 01 00 48 89 04 24
>>
>> According to kernel bisection, this problem became visible due to commit
>> f7f99100d8d9 which changes how struct pages are initialized.
>>
>> Memblock layout affects the pfn ranges covered by node/zone. Consider
>> that we have a VM with 2 NUMA nodes and each node has 4GB memory, and
>> the default (no memmap= given) memblock layout is like below:
>>
>> MEMBLOCK configuration:
>> memory size = 0x00000001fff75c00 reserved size = 0x000000000300c000
>> memory.cnt = 0x4
>> memory[0x0] [0x0000000000001000-0x000000000009efff], 0x000000000009e000 bytes on node 0 flags: 0x0
>> memory[0x1] [0x0000000000100000-0x00000000bffd6fff], 0x00000000bfed7000 bytes on node 0 flags: 0x0
>> memory[0x2] [0x0000000100000000-0x000000013fffffff], 0x0000000040000000 bytes on node 0 flags: 0x0
>> memory[0x3] [0x0000000140000000-0x000000023fffffff], 0x0000000100000000 bytes on node 1 flags: 0x0
>> ...
>>
>> If you give memmap=1G!4G (so it just covers memory[0x2]),
>> the range [0x100000000-0x13fffffff] is gone:
>>
>> MEMBLOCK configuration:
>> memory size = 0x00000001bff75c00 reserved size = 0x000000000300c000
>> memory.cnt = 0x3
>> memory[0x0] [0x0000000000001000-0x000000000009efff], 0x000000000009e000 bytes on node 0 flags: 0x0
>> memory[0x1] [0x0000000000100000-0x00000000bffd6fff], 0x00000000bfed7000 bytes on node 0 flags: 0x0
>> memory[0x2] [0x0000000140000000-0x000000023fffffff], 0x0000000100000000 bytes on node 1 flags: 0x0
>> ...
>>
>> This causes shrinking node 0's pfn range because it is calculated by
>> the address range of memblock.memory. So some of struct pages in the
>> gap range are left uninitialized.
>>
>> We have a function zero_resv_unavail() which does zeroing the struct
>> pages outside memblock.memory, but currently it covers only the reserved
>> unavailable range (i.e. memblock.memory && !memblock.reserved).
>> This patch extends it to cover all unavailable range, which fixes
>> the reported issue.
>>
>> Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap")
>> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
>> Tested-by: Oscar Salvador <osalvador@...e.de>
>> Tested-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
>
> Reviewed-by: Pavel Tatashin <pavel.tatashin@...rosoft.com>
>
> Also, please review and add the following patch to this series:
>
> From 6d23e66e979244734a06c1b636742c2568121b39 Mon Sep 17 00:00:00 2001
> From: Pavel Tatashin <pavel.tatashin@...rosoft.com>
> Date: Mon, 27 Aug 2018 19:10:35 -0400
> Subject: [PATCH] mm: return zero_resv_unavail optimization
>
> When checking for valid pfns in zero_resv_unavail(), it is not necessary to
> verify that pfns within pageblock_nr_pages ranges are valid, only the first
> one needs to be checked. This is because memory for pages are allocated in
> contiguous chunks that contain pageblock_nr_pages struct pages.
>
> Signed-off-by: Pavel Tatashin <pavel.tatashin@...rosoft.com>
> ---
> mm/page_alloc.c | 46 ++++++++++++++++++++++++++--------------------
> 1 file changed, 26 insertions(+), 20 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 650d8f16a67e..5dfc206db40e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6441,6 +6441,29 @@ void __init free_area_init_node(int nid, unsigned long *zones_size,
> }
>
> #if defined(CONFIG_HAVE_MEMBLOCK) && !defined(CONFIG_FLAT_NODE_MEM_MAP)
> +
> +/*
> + * Zero all valid struct pages in range [spfn, epfn), return number of struct
> + * pages zeroed
> + */
> +static u64 zero_pfn_range(unsigned long spfn, unsigned long epfn)
> +{
> + unsigned long pfn;
> + u64 pgcnt = 0;
> +
> + for (pfn = spfn; pfn < epfn; pfn++) {
> + if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) {
> + pfn = ALIGN_DOWN(pfn, pageblock_nr_pages)
> + + pageblock_nr_pages - 1;
> + continue;
> + }
> + mm_zero_struct_page(pfn_to_page(pfn));
> + pgcnt++;
> + }
> +
> + return pgcnt;
> +}
> +
> /*
> * Only struct pages that are backed by physical memory are zeroed and
> * initialized by going through __init_single_page(). But, there are some
> @@ -6456,7 +6479,6 @@ void __init free_area_init_node(int nid, unsigned long *zones_size,
> void __init zero_resv_unavail(void)
> {
> phys_addr_t start, end;
> - unsigned long pfn;
> u64 i, pgcnt;
> phys_addr_t next = 0;
>
> @@ -6466,34 +6488,18 @@ void __init zero_resv_unavail(void)
> pgcnt = 0;
> for_each_mem_range(i, &memblock.memory, NULL,
> NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end, NULL) {
> - if (next < start) {
> - for (pfn = PFN_DOWN(next); pfn < PFN_UP(start); pfn++) {
> - if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages)))
> - continue;
> - mm_zero_struct_page(pfn_to_page(pfn));
> - pgcnt++;
> - }
> - }
> + if (next < start)
> + pgcnt += zero_pfn_range(PFN_DOWN(next), PFN_UP(start));
> next = end;
> }
> - for (pfn = PFN_DOWN(next); pfn < max_pfn; pfn++) {
> - if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages)))
> - continue;
> - mm_zero_struct_page(pfn_to_page(pfn));
> - pgcnt++;
> - }
> -
> + pgcnt += zero_pfn_range(PFN_DOWN(next), max_pfn);
>
> /*
> * Struct pages that do not have backing memory. This could be because
> * firmware is using some of this memory, or for some other reasons.
> - * Once memblock is changed so such behaviour is not allowed: i.e.
> - * list of "reserved" memory must be a subset of list of "memory", then
> - * this code can be removed.
> */
> if (pgcnt)
> pr_info("Zeroed struct page in unavailable ranges: %lld pages", pgcnt);
> -
> }
> #endif /* CONFIG_HAVE_MEMBLOCK && !CONFIG_FLAT_NODE_MEM_MAP */
>
>
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