This patch adds the values related to buddy system to vmcoreinfo data so that makedumpfile (dump filtering command) can filter out all free pages with the new logic. It's faster than the current logic because it can distinguish free page by analyzing page structure at the same time as filtering for other unnecessary pages (e.g. anonymous page). OTOH, the current logic has to trace free_list to distinguish free pages while analyzing page structure to filter out other unnecessary pages. The new logic uses the fact that buddy page is marked by _mapcount == PAGE_BUDDY_MAPCOUNT_VALUE. But, _mapcount shares its memory with other fields for SLAB/SLUB when PG_slab is set, so we need to check if PG_slab is set or not before looking up _mapcount value. And we can get the order of buddy system from private field. To sum it up, the values below are required for this logic. Required values: - OFFSET(page._mapcount) - OFFSET(page.private) - NUMBER(PG_slab) - NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE) Changelog from v1 to v2: 1. remove SIZE(pageflags) The new logic was changed after I sent v1 patch. Accordingly, SIZE(pageflags) has been unnecessary for makedumpfile. What's makedumpfile: makedumpfile creates a small dumpfile by excluding unnecessary pages for the analysis. To distinguish unnecessary pages, makedumpfile gets the vmcoreinfo data which has the minimum debugging information only for dump filtering. Signed-off-by: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp> --- kernel/kexec.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/kexec.c b/kernel/kexec.c index 5e4bd78..b27efe4 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -1490,6 +1490,8 @@ static int __init crash_save_vmcoreinfo_init(void) VMCOREINFO_OFFSET(page, _count); VMCOREINFO_OFFSET(page, mapping); VMCOREINFO_OFFSET(page, lru); + VMCOREINFO_OFFSET(page, _mapcount); + VMCOREINFO_OFFSET(page, private); VMCOREINFO_OFFSET(pglist_data, node_zones); VMCOREINFO_OFFSET(pglist_data, nr_zones); #ifdef CONFIG_FLAT_NODE_MEM_MAP @@ -1512,6 +1514,8 @@ static int __init crash_save_vmcoreinfo_init(void) VMCOREINFO_NUMBER(PG_lru); VMCOREINFO_NUMBER(PG_private); VMCOREINFO_NUMBER(PG_swapcache); + VMCOREINFO_NUMBER(PG_slab); + VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE); arch_crash_save_vmcoreinfo(); update_vmcoreinfo_note(); -- 1.7.9.2
