|| ||Christoph Lameter <email@example.com>|
|| ||[PATCH 0/5] Direct Migration V6: Overview|
|| ||Wed, 30 Nov 2005 09:10:57 -0800 (PST)|
|| ||KAMEZAWA Hiroyuki <firstname.lastname@example.org>,
email@example.com, Cliff Wickman <firstname.lastname@example.org>,
Christoph Lameter <email@example.com>,
Direct page migration allows to avoid using swap space for migration. This
patch does not add any additional APIs, it just improves the way page
Benefits over swap migration:
1. Its faster because the page does not need to be written to swap space.
2. It does not use swap space and therefore there is no danger of running
out of swap space.
3. The need to write back a dirty page before migration is avoided through
a file system specific method making page migration even faster. We
fall back to writeout if the filesystem does not have such a method
4. Direct migration allows the preservation of the relative location of a page
within a set of nodes. This means that special placement of pages
for a performance critical application can be preserved when migrating.
Swap migration will rearrange the pages as they are swapped in which
may destroy the prior arrangement.
Many of the ideas for this code were originally developed in the memory
hotplug project and we hope that this code also will allow the hotplug
project to build on this patch in order to get to their goals. We also
would like to be able to move bad memory at SGI. IA64 arch specific code
to handle bad memory exists in 2.6.15 but that code is currently not able
to migrate pages.
The patchset consists of five patches (only the first two are necessary to
have basic direct migration support):
1. SwapCache patch
SwapCache pages may have changed their type after lock_page() if the
page was migrated. Check for this and retry lookup if the page is no
longer a SwapCache page.
Basic direct migration with fallback to swap if all other attempts
Page migration installs swap ptes for anonymous pages in order to
preserve the information contained in the page tables. This patch
removes the swap ptes after migration and replaces them with regular
4. upgrade of MPOL_MF_MOVE and sys_migrate_pages()
Add logic to mm/mempolicy.c to allow the policy layer to control
direct page migration. Thanks to Paul Jackson for the interative
logic to move between sets of nodes.
5. buffer_migrate_pages() patch
Allow migration without writing back dirty pages. Add filesystem dependent
migration support for ext2/ext3 and xfs. Use swapper space to setup a
method to migrate anonymous pages without writeback.
Credits (also in mm/vmscan.c):
The idea for this scheme of page migration was first developed in the context
of the memory hotplug project. The main authors of the migration code from
the memory hotplug project are:
IWAMOTO Toshihiro <firstname.lastname@example.org>
Hirokazu Takahashi <email@example.com>
Dave Hansen <firstname.lastname@example.org>
- Patchset against 2.6.15-rc3-mm1
- Remove checks for page count increases while migrating after Andrew assured
me that this cannot happen. Revise documentation to reflect that. If this is
the case then we will have no need to include the unwind code from the
hotplug project in the future.
- Wrong reference while calling remove_from_swap to page instead of newpage
- Patchset against 2.6.15-rc2-mm1
- Update policy layer patch to use the generic check_range in 2.6.15-rc2-mm1.
- Remove try_to_unmap patch since VM_RESERVED vanished under us and therefore
there is no point anymore to distinguish between permament and transitional
- Patchset against 2.6.15-rc1-mm2 + two swap migration fixes posted today.
- Remove what is already in 2.6.14-rc1-mm2 which results in a significant
cleanup of the code.
- Patchset against 2.6.14-mm2
- Fix single processor build and builds without CONFIG_MIGRATION
- export symbols for filesystems that are modules and for
modules using migrate_pages().
- Paul Jackson's cpuset migration support is in 2.6.14-mm2 so
this patchset can be easily applied to -mm2 to get from swap
based to direct page migration.
- Call node_remap with the right parameters in do_migrate_pages().
- Take radix tree lock while examining page count to avoid races with
find_get_page() and various *_get_pages based on it.
- Convert direct ptes to swap ptes before radix tree update to avoid
- Fix problem if CONFIG_MIGRATION is off for buffer_migrate_page
- Add documentation about page migration
- Change migrate_pages() api so that the caller can decide what
to do about the migrated pages (badmem handling and hotplug
have to remove those pages for good).
- Drop config patch (already in mm)
- Add try_to_unmap patch
- Patchset now against 2.6.14-mm1 without requiring additional patches.
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