On Tue, 27 Nov 2012 15:00:48 +0900
Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp> wrote:
> Hello HATAYAMA-san,
>
> On Fri, 16 Nov 2012 14:02:13 +0900
> HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> wrote:
>
> > On kernels from v2.6.18 to v2.6.37, buddy page is marked by the
> > PG_buddy flag.
> >
> > kernel version | PG_buddy
> > ------------------ +---------------------------------
> > v2.6.17 to v2.6.26 | 19
> > v2.6.27 to v2.6.37 | 19 if CONFIG_PAGEFLAGS_EXTEND=y
> > | 18 otherwise
Additionally, PG_private_2 was introduced in v2.6.30 with the commit
below:
commit 266cf658efcf6ac33541a46740f74f50c79d2b6b
Author: David Howells <dhowells at redhat.com>
Date: Fri Apr 3 16:42:36 2009 +0100
FS-Cache: Recruit a page flags for cache management
Recruit a page flag to aid in cache management. The following extra flag is
defined:
(1) PG_fscache (PG_private_2)
Therefore, PG_buddy varies as below:
kernel version | PG_buddy
------------------ +---------------------------------
v2.6.27 to v2.6.29 | 18 if CONFIG_PAGEFLAGS_EXTEND=y
| 17 otherwise
v2.6.30 to v2.6.37 | 19 if CONFIG_PAGEFLAGS_EXTEND=y
| 18 otherwise
Thanks
Atsushi Kumagai
> > We don't need to care about CONFIG_PAGEFLAGS_EXTEND because the
> > architectures specifying this as y are um and xtensa only. They are
> > not included in the supported architectures of makedumpfile.
>
> Sorry for too late point out.
>
> I did regression test for v1.5.1 on x86_64 machine in the last weekend
> and found the issue that page_is_buddy_v2() can't exclude free pages
> correctly for kernel 2.6.30 to 2.6.37.
> I checked the configuration of these kernels, I made sure that
> CONFIG_PAGEFLAGS_EXTENDED was set as y, so PG_buddy=18 is invalid for them.
>
> According to this fact, PG_buddy is variable for the supported architectures
> of makedumpfile, too.
> So, how did you confirm that CONFIG_PAGEFLAGS_EXTENDED is only related with
> um and xtensa ?
>
> And why did you test with PG_buddy=19 for 2.6.32 when you posted this patch set?
>
> > - 2.6.32
> > NUMBER(PG_slab)=7
> > NUMBER(PG_buddy)=19
> > OFFSET(page._mapcount)=12
> > OFFSET(page.private)=16
> > SIZE(pageflags)=4
>
>
> Thanks
> Atsushi Kumagai
>
> > Signed-off-by: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com>
> > ---
> >
> > makedumpfile.c | 24 ++++++++++++++++++++----
> > 1 files changed, 20 insertions(+), 4 deletions(-)
> >
> > diff --git a/makedumpfile.c b/makedumpfile.c
> > index 7b13dca..4e5d4d3 100644
> > --- a/makedumpfile.c
> > +++ b/makedumpfile.c
> > @@ -3669,6 +3669,19 @@ exclude_free_page(void)
> > }
> >
> > /*
> > + * For the kernel versions from v2.6.17 to v2.6.37.
> > + */
> > +static int
> > +page_is_buddy_v2(unsigned long flags, unsigned int _mapcount,
> > + unsigned long private, unsigned int _count)
> > +{
> > + if (flags & (1UL << NUMBER(PG_buddy)))
> > + return TRUE;
> > +
> > + return FALSE;
> > +}
> > +
> > +/*
> > * For v2.6.38 and later kernel versions.
> > */
> > static int
> > @@ -3690,10 +3703,13 @@ setup_page_is_buddy(void)
> > if (OFFSET(page.private) == NOT_FOUND_STRUCTURE)
> > goto out;
> >
> > - if (NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE) != NOT_FOUND_NUMBER) {
> > - if (OFFSET(page._mapcount) != NOT_FOUND_STRUCTURE)
> > - info->page_is_buddy = page_is_buddy_v3;
> > - }
> > + if (NUMBER(PG_buddy) == NOT_FOUND_NUMBER) {
> > + if (NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE) != NOT_FOUND_NUMBER) {
> > + if (OFFSET(page._mapcount) != NOT_FOUND_STRUCTURE)
> > + info->page_is_buddy = page_is_buddy_v3;
> > + }
> > + } else
> > + info->page_is_buddy = page_is_buddy_v2;
> >
> > out:
> > if (!info->page_is_buddy)
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
