On Mon, Dec 10, 2012 at 10:39:13AM +0900, Atsushi Kumagai wrote: > 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> Looks good to me. Acked-by: Vivek Goyal <vgoyal at redhat.com> Thanks Vivek > --- > 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 > > _______________________________________________ > kexec mailing list > kexec at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec
