Hello Petr,
>When multiple pages are excluded from the dump, store the extents in
>struct cycle and check if anything is still pending on the next invocation
>of __exclude_unnecessary_pages. This assumes that:
>
> 1. after __exclude_unnecessary_pages is called for a struct mem_map_data
> that extends beyond the current cycle, it is not called again during
> that cycle,
> 2. in the next cycle, __exclude_unnecessary_pages is not called before
> this final struct mem_map_data.
>
>Both assumptions are met if struct mem_map_data segments:
>
> 1. do not overlap,
> 2. are sorted by physical address in ascending order.
In ELF case, write_elf_pages_cyclic() processes PT_LOAD entries from
PT_LOAD(0), this can break both assumptions unluckily.
Actually this patch doesn't work on my machine:
LOAD (0)
phys_start : 1000000
phys_end : 182f000
virt_start : ffffffff81000000
virt_end : ffffffff8182f000
LOAD (1)
phys_start : 1000
phys_end : 9b400
virt_start : ffff810000001000
virt_end : ffff81000009b400
LOAD (2)
phys_start : 100000
phys_end : 27000000
virt_start : ffff810000100000
virt_end : ffff810027000000
LOAD (3)
phys_start : 37000000
phys_end : cff70000
virt_start : ffff810037000000
virt_end : ffff8100cff70000
LOAD (4)
phys_start : 100000000
phys_end : 170000000
virt_start : ffff810100000000
virt_end : ffff810170000000
PT_LOAD(2) includes PT_LOAD(0) and there physical addresses aren't sorted.
If there is the only "sort issue", it may easy to fix it with a new iterator
like "for_each_pt_load()", it iterates PT_LOAD entries in ascending order
by physical address.
However, I don't have a good idea to solve the overlap issue now...
Thanks
Atsushi Kumagai
>These two conditions are true for all supported memory models.
>
>Note that the start PFN of the excluded extent is set to the end of the
>current cycle (which is equal to the start of the next cycle, see
>update_cycle), so only the part of the excluded region which falls beyond
>current cycle buffer is valid. If the excluded region is completely
>processed in the current cycle, the start PFN is bigger than the end PFN
>and no work is done at the beginning of the next cycle.
>
>After processing the leftover from last cycle, pfn_start and mem_map are
>adjusted to skip the excluded pages. There is no check whether the
>adjusted pfn_start is within the current cycle. Nothing bad happens if
>it isn't, because pages outside the current cyclic region are ignored by
>the subsequent loop, and the remainder is postponed to the next cycle by
>exclude_range().
>
>Signed-off-by: Petr Tesarik <ptesarik at suse.cz>
>---
> makedumpfile.c | 49 +++++++++++++++++++++++++++++++++++--------------
> makedumpfile.h | 5 +++++
> 2 files changed, 40 insertions(+), 14 deletions(-)
>
>diff --git a/makedumpfile.c b/makedumpfile.c
>index 16081a5..a3498e4 100644
>--- a/makedumpfile.c
>+++ b/makedumpfile.c
>@@ -4667,6 +4667,26 @@ initialize_2nd_bitmap_cyclic(struct cycle *cycle)
> return TRUE;
> }
>
>+static void
>+exclude_range(mdf_pfn_t *counter, mdf_pfn_t pfn, mdf_pfn_t endpfn,
>+ struct cycle *cycle)
>+{
>+ if (cycle) {
>+ cycle->exclude_pfn_start = cycle->end_pfn;
>+ cycle->exclude_pfn_end = endpfn;
>+ cycle->exclude_pfn_counter = counter;
>+
>+ if (cycle->end_pfn < endpfn)
>+ endpfn = cycle->end_pfn;
>+ }
>+
>+ while (pfn < endpfn) {
>+ if (clear_bit_on_2nd_bitmap_for_kernel(pfn, cycle))
>+ (*counter)++;
>+ ++pfn;
>+ }
>+}
>+
> int
> __exclude_unnecessary_pages(unsigned long mem_map,
> mdf_pfn_t pfn_start, mdf_pfn_t pfn_end, struct cycle *cycle)
>@@ -4681,6 +4701,18 @@ __exclude_unnecessary_pages(unsigned long mem_map,
> unsigned long flags, mapping, private = 0;
>
> /*
>+ * If a multi-page exclusion is pending, do it first
>+ */
>+ if (cycle && cycle->exclude_pfn_start < cycle->exclude_pfn_end) {
>+ exclude_range(cycle->exclude_pfn_counter,
>+ cycle->exclude_pfn_start, cycle->exclude_pfn_end,
>+ cycle);
>+
>+ mem_map += (cycle->exclude_pfn_end - pfn_start) * SIZE(page);
>+ pfn_start = cycle->exclude_pfn_end;
>+ }
>+
>+ /*
> * Refresh the buffer of struct page, when changing mem_map.
> */
> pfn_read_start = ULONGLONG_MAX;
>@@ -4744,21 +4776,10 @@ __exclude_unnecessary_pages(unsigned long mem_map,
> if ((info->dump_level & DL_EXCLUDE_FREE)
> && info->page_is_buddy
> && info->page_is_buddy(flags, _mapcount, private, _count)) {
>- int i, nr_pages = 1 << private;
>+ int nr_pages = 1 << private;
>+
>+ exclude_range(&pfn_free, pfn, pfn + nr_pages, cycle);
>
>- for (i = 0; i < nr_pages; ++i) {
>- /*
>- * According to combination of
>- * MAX_ORDER and size of cyclic
>- * buffer, this clearing bit operation
>- * can overrun the cyclic buffer.
>- *
>- * See check_cyclic_buffer_overrun()
>- * for the detail.
>- */
>- if (clear_bit_on_2nd_bitmap_for_kernel((pfn + i), cycle))
>- pfn_free++;
>- }
> pfn += nr_pages - 1;
> mem_map += (nr_pages - 1) * SIZE(page);
> }
>diff --git a/makedumpfile.h b/makedumpfile.h
>index eb03688..43cf91d 100644
>--- a/makedumpfile.h
>+++ b/makedumpfile.h
>@@ -1593,6 +1593,11 @@ int get_xen_info_ia64(void);
> struct cycle {
> mdf_pfn_t start_pfn;
> mdf_pfn_t end_pfn;
>+
>+ /* for excluding multi-page regions */
>+ mdf_pfn_t exclude_pfn_start;
>+ mdf_pfn_t exclude_pfn_end;
>+ mdf_pfn_t *exclude_pfn_counter;
> };
>
> static inline int
>--
>1.8.4.5
