> From: kexec-bounces at lists.infradead.org > [mailto:kexec-bounces at lists.infradead.org] On Behalf Of Atsushi Kumagai > Sent: Tuesday, November 27, 2012 3:01 PM > Subject: Re: [PATCH v2 08/10] Add page_is_buddy for PG_buddy > > 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 > > > > 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 ? > I guess I used git grep on different kernel source tree. > 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 > Sorry, I was not aware of this. Anyway, the current hard-coded values doesn't work at all since before talking about PG_buddy, we cannot get values of page structure's members, such as offset value of private member, so non-cyclic is always used instead. How about dropping hard-coded values? Thanks. HATAYAMA, Daisuke
