• Christoph Lameter's avatar
    [PATCH] Swap Migration V5: migrate_pages() function · 49d2e9cc
    Christoph Lameter authored
    This adds the basic page migration function with a minimal implementation that
    only allows the eviction of pages to swap space.
    
    Page eviction and migration may be useful to migrate pages, to suspend
    programs or for remapping single pages (useful for faulty pages or pages with
    soft ECC failures)
    
    The process is as follows:
    
    The function wanting to migrate pages must first build a list of pages to be
    migrated or evicted and take them off the lru lists via isolate_lru_page().
    isolate_lru_page determines that a page is freeable based on the LRU bit set.
    
    Then the actual migration or swapout can happen by calling migrate_pages().
    
    migrate_pages does its best to migrate or swapout the pages and does multiple
    passes over the list.  Some pages may only be swappable if they are not dirty.
     migrate_pages may start writing out dirty pages in the initial passes over
    the pages.  However, migrate_pages may not be able to migrate or evict all
    pages for a variety of reasons.
    
    The remaining pages may be returned to the LRU lists using putback_lru_pages().
    
    Changelog V4->V5:
    - Use the lru caches to return pages to the LRU
    
    Changelog V3->V4:
    - Restructure code so that applying patches to support full migration does
      require minimal changes. Rename swapout_pages() to migrate_pages().
    
    Changelog V2->V3:
    - Extract common code from shrink_list() and swapout_pages()
    Signed-off-by: default avatarMike Kravetz <kravetz@us.ibm.com>
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
    Cc: "Michael Kerrisk" <mtk-manpages@gmx.net>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    49d2e9cc
vmscan.c 40.3 KB