• R
    [PATCH] swsusp: Improve handling of highmem · 8357376d
    Rafael J. Wysocki 提交于
    Currently swsusp saves the contents of highmem pages by copying them to the
    normal zone which is quite inefficient (eg.  it requires two normal pages
    to be used for saving one highmem page).  This may be improved by using
    highmem for saving the contents of saveable highmem pages.
    
    Namely, during the suspend phase of the suspend-resume cycle we try to
    allocate as many free highmem pages as there are saveable highmem pages.
    If there are not enough highmem image pages to store the contents of all of
    the saveable highmem pages, some of them will be stored in the "normal"
    memory.  Next, we allocate as many free "normal" pages as needed to store
    the (remaining) image data.  We use a memory bitmap to mark the allocated
    free pages (ie.  highmem as well as "normal" image pages).
    
    Now, we use another memory bitmap to mark all of the saveable pages
    (highmem as well as "normal") and the contents of the saveable pages are
    copied into the image pages.  Then, the second bitmap is used to save the
    pfns corresponding to the saveable pages and the first one is used to save
    their data.
    
    During the resume phase the pfns of the pages that were saveable during the
    suspend are loaded from the image and used to mark the "unsafe" page
    frames.  Next, we try to allocate as many free highmem page frames as to
    load all of the image data that had been in the highmem before the suspend
    and we allocate so many free "normal" page frames that the total number of
    allocated free pages (highmem and "normal") is equal to the size of the
    image.  While doing this we have to make sure that there will be some extra
    free "normal" and "safe" page frames for two lists of PBEs constructed
    later.
    
    Now, the image data are loaded, if possible, into their "original" page
    frames.  The image data that cannot be written into their "original" page
    frames are loaded into "safe" page frames and their "original" kernel
    virtual addresses, as well as the addresses of the "safe" pages containing
    their copies, are stored in one of two lists of PBEs.
    
    One list of PBEs is for the copies of "normal" suspend pages (ie.  "normal"
    pages that were saveable during the suspend) and it is used in the same way
    as previously (ie.  by the architecture-dependent parts of swsusp).  The
    other list of PBEs is for the copies of highmem suspend pages.  The pages
    in this list are restored (in a reversible way) right before the
    arch-dependent code is called.
    Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
    Cc: Pavel Machek <pavel@ucw.cz>
    Signed-off-by: NAndrew Morton <akpm@osdl.org>
    Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
    8357376d
suspend.h 1.6 KB