• Arjan van de Ven's avatar
    device model: Do a quickcheck for driver binding before doing an expensive check · 6cd49586
    Arjan van de Ven authored
    This patch adds a quick check for the driver<->device match before
    taking the locks and doin gthe expensive checks. Taking the lock hurts
    in asynchronous boot context where the device lock gets hit; one of the
    init functions takes the lock and goes to do an expensive hardware init;
    the other init functions walk the same PCI list and get stuck on the
    lock as a result.
    
    For the common case, we can know there's no chance whatsoever of a match
    if the device isn't in the drivers ID table... so this patch does that
    check as a best-effort-avoid-the-lock approach.
    
    Bootcharts for before and after can be seen at
    http://www.fenrus.org/before.svg
    http://www.fenrus.org/after.svg
    
    Note the long time "agp_ali_init" takes in the first graph; my laptop
    doesn't even have an ALI chip in it!  (the bootgraphs look a bit
    dissimilar, but that's the point, the first one has a bunch of arbitrary
    delays in it that cause it to look very different)
    
    This reduces my kernel boot time by about 20%
    Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
    Cc: Alan Stern <stern@rowland.harvard.edu>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    6cd49586
dd.c 8.98 KB