On Fri, Jun 15, 2018 at 5:48 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 15 Jun 2018 11:57:33 -0400 Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> wrote: > > > The role of zero_resv_unavail() is to make sure that every struct page that > > is allocated but is not backed by memory that is accessible by kernel is > > zeroed and not in some uninitialized state. > > > > Since struct pages are allocated in blocks (2M pages in x86 case), we can > > skip pageblock_nr_pages at a time, when the first one is found to be > > invalid. > > > > This optimization may help since now on x86 every hole in e820 maps > > is marked as reserved in memblock, and thus will go through this function. > > > > This function is called before sched_clock() is initialized, so I used my > > x86 early boot clock patches to measure the performance improvement. > > > > With 1T hole on i7-8700 currently we would take 0.606918s of boot time, but > > with this optimization 0.001103s. > > This conflicts with mm-zero-remaining-unavailable-struct-pages.patch, below. Hi Andrew, mm-zero-remaining-unavailable-struct-pages.patch should be replaced by newer version: http://lkml.kernel.org/r/20180615072947.GB23273@xxxxxxxxxxxxxxxxxxxxxxxxxxxx The v3 "[PATCH] x86/e820: put !E820_TYPE_RAM regions into memblock.reserved" was acked by michal and also I reviewed it. My patch does not conflict with this newer version, and intends to help the newer version as there is now potentially more work for zero_resv_unavail(). Thank you, Pavel > > mm-zero-remaining-unavailable-struct-pages.patch (which you have yet to > review, please) fixes an oops and is rather higher priority. > > > > From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Subject: mm: zero remaining unavailable struct pages > > 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. > > Link: http://lkml.kernel.org/r/20180613054107.GA5329@xxxxxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap") > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Tested-by: Oscar Salvador <osalvador@xxxxxxx> > Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> > Cc: Steven Sistare <steven.sistare@xxxxxxxxxx> > Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Cc: Huang Ying <ying.huang@xxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > include/linux/memblock.h | 16 ---------------- > mm/page_alloc.c | 33 ++++++++++++++++++++++++--------- > 2 files changed, 24 insertions(+), 25 deletions(-) > > diff -puN include/linux/memblock.h~mm-zero-remaining-unavailable-struct-pages include/linux/memblock.h > --- a/include/linux/memblock.h~mm-zero-remaining-unavailable-struct-pages > +++ a/include/linux/memblock.h > @@ -236,22 +236,6 @@ void __next_mem_pfn_range(int *idx, int > for_each_mem_range_rev(i, &memblock.memory, &memblock.reserved, \ > nid, flags, p_start, p_end, p_nid) > > -/** > - * for_each_resv_unavail_range - iterate through reserved and unavailable memory > - * @i: u64 used as loop variable > - * @flags: pick from blocks based on memory attributes > - * @p_start: ptr to phys_addr_t for start address of the range, can be %NULL > - * @p_end: ptr to phys_addr_t for end address of the range, can be %NULL > - * > - * Walks over unavailable but reserved (reserved && !memory) areas of memblock. > - * Available as soon as memblock is initialized. > - * Note: because this memory does not belong to any physical node, flags and > - * nid arguments do not make sense and thus not exported as arguments. > - */ > -#define for_each_resv_unavail_range(i, p_start, p_end) \ > - for_each_mem_range(i, &memblock.reserved, &memblock.memory, \ > - NUMA_NO_NODE, MEMBLOCK_NONE, p_start, p_end, NULL) > - > static inline void memblock_set_region_flags(struct memblock_region *r, > unsigned long flags) > { > diff -puN mm/page_alloc.c~mm-zero-remaining-unavailable-struct-pages mm/page_alloc.c > --- a/mm/page_alloc.c~mm-zero-remaining-unavailable-struct-pages > +++ a/mm/page_alloc.c > @@ -6390,25 +6390,40 @@ void __paginginit free_area_init_node(in > * struct pages which are reserved in memblock allocator and their fields > * may be accessed (for example page_to_pfn() on some configuration accesses > * flags). We must explicitly zero those struct pages. > + * > + * This function also addresses a similar issue where struct pages are left > + * uninitialized because the physical address range is not covered by > + * memblock.memory or memblock.reserved. That could happen when memblock > + * layout is manually configured via memmap=. > */ > void __paginginit zero_resv_unavail(void) > { > phys_addr_t start, end; > unsigned long pfn; > u64 i, pgcnt; > + phys_addr_t next = 0; > > /* > - * Loop through ranges that are reserved, but do not have reported > - * physical memory backing. > + * Loop through unavailable ranges not covered by memblock.memory. > */ > pgcnt = 0; > - for_each_resv_unavail_range(i, &start, &end) { > - for (pfn = PFN_DOWN(start); pfn < PFN_UP(end); pfn++) { > - if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) > - continue; > - mm_zero_struct_page(pfn_to_page(pfn)); > - pgcnt++; > + 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++; > + } > } > + 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++; > } > > /* > @@ -6419,7 +6434,7 @@ void __paginginit zero_resv_unavail(void > * this code can be removed. > */ > if (pgcnt) > - pr_info("Reserved but unavailable: %lld pages", pgcnt); > + pr_info("Zeroed struct page in unavailable ranges: %lld pages", pgcnt); > } > #endif /* CONFIG_HAVE_MEMBLOCK */ > > _ >
