Messages in this thread Patch in this message | | | Date | Wed, 20 May 2020 22:51:10 +0300 | From | Mike Rapoport <> | Subject | Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables |
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On Wed, May 20, 2020 at 12:03:31PM -0700, Guenter Roeck wrote: > On 5/20/20 10:03 AM, Mike Rapoport wrote: > > On Mon, May 18, 2020 at 09:37:15AM +0100, Will Deacon wrote: > >> On Sat, May 16, 2020 at 05:07:50PM -0700, Guenter Roeck wrote: > >>> On Sat, May 16, 2020 at 05:00:50PM -0700, Guenter Roeck wrote: > >>>> On Mon, May 11, 2020 at 09:41:36PM +0100, Will Deacon wrote: > >>>>> Now that the page table allocator can free page table allocations > >>>>> smaller than PAGE_SIZE, reduce the size of the PMD and PTE allocations > >>>>> to avoid needlessly wasting memory. > >>>>> > >>>>> Cc: "David S. Miller" <davem@davemloft.net> > >>>>> Cc: Peter Zijlstra <peterz@infradead.org> > >>>>> Signed-off-by: Will Deacon <will@kernel.org> > >>>> > >>>> Something in the sparc32 patches in linux-next causes all my sparc32 emulations > >>>> to crash. bisect points to this patch, but reverting it doesn't help, and neither > >>>> does reverting the rest of the series. > >>>> > >>> Actually, turns out I see the same pattern (lots of scheduling while atomic > >>> followed by 'killing interrupt handler' in cryptomgr_test) with several > >>> powerpc boot tests. I am currently bisecting those crashes. I'll report > >>> the results here as well as soon as I have it. > >> > >> FWIW, I retested my sparc32 patches with PREEMPT=y and I don't see any > >> issues. However, linux-next is a different story, where I don't get very far > >> at all: > >> > >> BUG: Bad page state in process swapper pfn:005b4 > > > > This is caused by c03584e30534 ("mm: memmap_init: iterate over memblock > > regions rather that check each PFN"). The commit sha is valid for > > v5.7-rc6-mmots-2020-05-19-21-52, so it will change in a day or so :) > > > > As it seems, sparc32 never registered the memory occupied by the kernel > > image with memblock_add() and it only reserves this memory with > > meblock_reserve(). > > > > I don't know what would happen on real HW, but with > > > > qemu-system-sparc -kernel /path/to/kernel > > > > the memory occupied by the kernel is reserved in openbios and removed > > from mem.available. The prom setup code in the kernel used mem.available > > to set up the memory banks and essentially there is a hole for the > > memory occupied by the kernel. > > > > Later in bootmem_init() this memory is memblock_reserve()d. > > > > Before the problematic commit, memmap initialization would call > > __init_single_page() for the pages in that hole, the > > free_low_memory_core_early() would mark them as resrved and everything > > would be Ok. > > > > After the change in memmap initialization, the hole is skipped and the > > page structs for it are not inited. And when they are passed from > > memblock to page allocator as reserved it gets confused. > > > > Simply registering the memory occupied by the kernel with memblock_add() > > resolves this issue, at least for qemu-system-arm and I cannot see how > > it can harm any other setup. > > > > If all that makes sense I'll send a proper patch :) > > > > diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c > > index 906eda1158b4..3cb3dffcbcdc 100644 > > --- a/arch/sparc/mm/init_32.c > > +++ b/arch/sparc/mm/init_32.c > > @@ -193,6 +193,7 @@ unsigned long __init bootmem_init(unsigned long *pages_avail) > > /* Reserve the kernel text/data/bss. */ > > size = (start_pfn << PAGE_SHIFT) - phys_base; > > memblock_reserve(phys_base, size); > > + memblock_add(phys_base, size); > > > > size = memblock_phys_mem_size() - memblock_reserved_size(); > > *pages_avail = (size >> PAGE_SHIFT) - high_pages; > > > >> Will > > > > With above patch applied on top of Ira's patch, I get: > > BUG: spinlock recursion on CPU#0, S01syslogd/139 > lock: 0xf5448350, .magic: dead4ead, .owner: S01syslogd/139, .owner_cpu: 0 > CPU: 0 PID: 139 Comm: S01syslogd Not tainted 5.7.0-rc6-next-20200518-00002-gb178d2d56f29-dirty #1 > [f0067a64 : > do_raw_spin_lock+0xa8/0xd8 ] > [f00d5034 : > copy_page_range+0x328/0x804 ] > [f0025be4 : > dup_mm+0x334/0x434 ] > [f0027124 : > copy_process+0x1224/0x12b0 ] > [f0027344 : > _do_fork+0x54/0x30c ] > [f0027670 : > do_fork+0x5c/0x6c ] > [f000de44 : > sparc_do_fork+0x18/0x38 ] > [f000b7f4 : > do_syscall+0x34/0x40 ] > [5010cd4c : > 0x5010cd4c ] > > Looks like yet another problem.
I've checked the patch above on top of the mmots which already has Ira's patches and it booted fine. I've used sparc32_defconfig to build the kernel and qemu-system-sparc with default machine and CPU.
> I can not revert c03584e30534 because it results in a compile failure.
Here's the "revert" of c03584e30534:
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d001d61e64d5..c9d9d3f9ebf4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5901,6 +5901,42 @@ overlap_memmap_init(unsigned long zone, unsigned long *pfn) return false; } +#ifdef CONFIG_SPARSEMEM +/* Skip PFNs that belong to non-present sections */ +static inline __meminit unsigned long next_pfn(unsigned long pfn) +{ + const unsigned long section_nr = pfn_to_section_nr(++pfn); + + if (present_section_nr(section_nr)) + return pfn; + return section_nr_to_pfn(next_present_section_nr(section_nr)); +} +#else +static inline __meminit unsigned long next_pfn(unsigned long pfn) +{ + return pfn++; +} +#endif + +#ifdef CONFIG_NODES_SPAN_OTHER_NODES +/* Only safe to use early in boot when initialisation is single-threaded */ +static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node) +{ + int nid; + + nid = __early_pfn_to_nid(pfn, &early_pfnnid_cache); + if (nid >= 0 && nid != node) + return false; + return true; +} + +#else +static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node) +{ + return true; +} +#endif + /* * Initially all pages are reserved - free ones are freed * up by memblock_free_all() once the early boot process is @@ -5940,6 +5976,14 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, * function. They do not exist on hotplugged memory. */ if (context == MEMMAP_EARLY) { + if (!early_pfn_valid(pfn)) { + pfn = next_pfn(pfn); + continue; + } + if (!early_pfn_in_nid(pfn, nid)) { + pfn++; + continue; + } if (overlap_memmap_init(zone, &pfn)) continue; if (defer_init(nid, pfn, end_pfn)) @@ -6055,23 +6099,9 @@ static void __meminit zone_init_free_lists(struct zone *zone) } void __meminit __weak memmap_init(unsigned long size, int nid, - unsigned long zone, - unsigned long range_start_pfn) + unsigned long zone, unsigned long start_pfn) { - unsigned long start_pfn, end_pfn; - unsigned long range_end_pfn = range_start_pfn + size; - int i; - - for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) { - start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn); - end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn); - - if (end_pfn > start_pfn) { - size = end_pfn - start_pfn; - memmap_init_zone(size, nid, zone, start_pfn, - MEMMAP_EARLY, NULL); - } - } + memmap_init_zone(size, nid, zone, start_pfn, MEMMAP_EARLY, NULL); } static int zone_batchsize(struct zone *zone) > Guenter
-- Sincerely yours, Mike.
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