Hi!
[1.] One line summary of the problem:
__offline_isolated_pages may isolate too many pages
[2.] Full description of the problem/report:
While experimenting with remove_memory/online_pages, removing as few
pages as possible (pageblock_nr_pages, 512 on my box) I noticed that the
number of pages marked "reserved" increased even though both functions
did not indicate an error. Following the code it was clear that
__offline_isolated_pages marked twice as many pages as it should:
=== start paste (from dmesg) ===
Offlined Pages 512
remove from free list c00 1024 e00
=== end paste ===
The issue seems to be that __offline_isolated_pages blindly uses
page_order() to determine how many pages it should mark as reserved in
the current loop iteration, without checking if this would exceed the
limit set by end_pfn.
I'm not sure what the correct way to fix this would be - is memory
isolation supposed to touch the order of a page if it crosses the end
(or beginning!) of the range of pages to be isolated?
[3.] Keywords (i.e., modules, networking, kernel):
kernel mm memory-hotplug
[4.] Kernel information
[4.1.] Kernel version (from /proc/version):
Linux version 2.6.35-00002-g76c52bb (ingo@memtester) (gcc version 4.4.5
(Debian 4.4.5-6) ) #7 SMP Tue Dec 14 14:28:17 CET 2010
The diff between vanilla 2.6.35 and this version is available at
http://akana.de/memtest35.diff - the only changes are a reduced timeout
in remove_memory and a bunch of additional exported symbols.
[4.2.] Kernel .config file:
http://akana.de/config-memtest35
[5.] Most recent kernel version which did not have the bug:
Probably none
[8.] Environment
[8.1.] Software (add the output of the ver_linux script here)
Linux memtester 2.6.35-00002-g76c52bb #7 SMP Tue Dec 14 14:28:17 CET
2010 x86_64 GNU/Linux
Gnu C 4.4.5
Gnu make 3.81
binutils 2.20.1
util-linux (no fdformat on the system)
mount support
module-init-tools found
Linux C Library 2.11.2
Dynamic linker (ldd) 2.11.2
Procps 3.2.8
Kbd 1.15.2
Sh-utils 8.5
Modules Loaded phys_mem ipv6 pcspkr i2c_piix4 i2c_core shpchp e1000
Distribution is Debian testing if it matters
[8.2.] Processor information (from /proc/cpuinfo):
AMD Phenom 9650, but the system is running inside a VMWare Player
instance with just a single virtual CPU
[8.3.] Module information (from /proc/modules):
phys_mem 15068 0 - Live 0xffffffffa00d1000
ipv6 340746 24 - Live 0xffffffffa0068000
pcspkr 2022 0 - Live 0xffffffffa0062000
i2c_piix4 13334 0 - Live 0xffffffffa0059000
i2c_core 28244 1 i2c_piix4, Live 0xffffffffa004b000
shpchp 35612 0 - Live 0xffffffffa003b000
e1000 164575 0 - Live 0xffffffffa0000000
[8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem)
[8.5.] PCI information ('lspci -vvv' as root)
[8.6.] SCSI information (from /proc/scsi/scsi)
As far as I can tell irrelevant to this problem?
(forgot to copy those, will add later if neccessary)
-ik
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