Hi all,
This patchset moves MIGRATE_ISOLATE to a standalone bit to avoid
being overwritten during pageblock isolation process. Currently,
MIGRATE_ISOLATE is part of enum migratetype (in include/linux/mmzone.h),
thus, setting a pageblock to MIGRATE_ISOLATE overwrites its original
migratetype. This causes pageblock migratetype loss during
alloc_contig_range() and memory offline, especially when the process
fails due to a failed pageblock isolation and the code tries to undo the
finished pageblock isolations.
It is on top of mm-everything-2025-02-13-23-42.
In terms of performance for changing pageblock types, no performance
change is observed:
1. I used perf to collect stats of offlining and onlining all memory of a
200GB VM 10 times and see that set_pfnblock_flags_mask() takes about
0.13% of the whole process with and without this patchset across 3 runs.
2. I used perf to collect stats of dd from /dev/zero to a 200GB tmpfs file
and find get_pfnblock_flags_mask() takes about 0.30% of the process with and
without this patchset across 3 runs.
Design
===
Pageblock flags are read in words to achieve good performance and existing
pageblock flags take 4 bits per pageblock. To avoid a substantial change
to the pageblock flag code, pageblock flag bits are expanded to use 8
and MIGRATE_ISOLATE is moved to use the last bit (bit 7).
It might look like the pageblock flags have doubled the overhead, but in
reality, the overhead is only 1 byte per 2MB/4MB (based on pageblock config),
or 0.0000476 %.
Any comment and/or suggestion is welcome. Thanks.
Zi Yan (4):
mm/page_isolation: make page isolation a standalone bit.
mm/page_isolation: remove migratetype from
move_freepages_block_isolate()
mm/page_isolation: remove migratetype from undo_isolate_page_range()
mm/page_isolation: remove migratetype parameter from more functions.
drivers/virtio/virtio_mem.c | 3 +-
include/linux/gfp.h | 6 ++-
include/linux/mmzone.h | 18 +++++--
include/linux/page-isolation.h | 24 ++++++---
include/linux/pageblock-flags.h | 33 +++++++++++-
include/trace/events/kmem.h | 14 ++---
mm/cma.c | 2 +-
mm/memory_hotplug.c | 5 +-
mm/page_alloc.c | 96 ++++++++++++++++++++++++---------
mm/page_isolation.c | 66 +++++++++--------------
10 files changed, 175 insertions(+), 92 deletions(-)
--
2.47.2
