• Robin Holt's avatar
    memblock: introduce a for_each_reserved_mem_region iterator · 8e7a7f86
    Robin Holt authored
    Struct page initialisation had been identified as one of the reasons why
    large machines take a long time to boot. Patches were posted a long time ago
    to defer initialisation until they were first used.  This was rejected on
    the grounds it should not be necessary to hurt the fast paths. This series
    reuses much of the work from that time but defers the initialisation of
    memory to kswapd so that one thread per node initialises memory local to
    that node.
    
    After applying the series and setting the appropriate Kconfig variable I
    see this in the boot log on a 64G machine
    
    [    7.383764] kswapd 0 initialised deferred memory in 188ms
    [    7.404253] kswapd 1 initialised deferred memory in 208ms
    [    7.411044] kswapd 3 initialised deferred memory in 216ms
    [    7.411551] kswapd 2 initialised deferred memory in 216ms
    
    On a 1TB machine, I see
    
    [    8.406511] kswapd 3 initialised deferred memory in 1116ms
    [    8.428518] kswapd 1 initialised deferred memory in 1140ms
    [    8.435977] kswapd 0 initialised deferred memory in 1148ms
    [    8.437416] kswapd 2 initialised deferred memory in 1148ms
    
    Once booted the machine appears to work as normal. Boot times were measured
    from the time shutdown was called until ssh was available again.  In the
    64G case, the boot time savings are negligible. On the 1TB machine, the
    savings were 16 seconds.
    
    Nate Zimmer said:
    
    : On an older 8 TB box with lots and lots of cpus the boot time, as
    : measure from grub to login prompt, the boot time improved from 1484
    : seconds to exactly 1000 seconds.
    
    Waiman Long said:
    
    : I ran a bootup timing test on a 12-TB 16-socket IvyBridge-EX system.  From
    : grub menu to ssh login, the bootup time was 453s before the patch and 265s
    : after the patch - a saving of 188s (42%).
    
    Daniel Blueman said:
    
    : On a 7TB, 1728-core NumaConnect system with 108 NUMA nodes, we're seeing
    : stock 4.0 boot in 7136s.  This drops to 2159s, or a 70% reduction with
    : this patchset.  Non-temporal PMD init (https://lkml.org/lkml/2015/4/23/350)
    : drops this to 1045s.
    
    This patch (of 13):
    
    As part of initializing struct page's in 2MiB chunks, we noticed that at
    the end of free_all_bootmem(), there was nothing which had forced the
    reserved/allocated 4KiB pages to be initialized.
    
    This helper function will be used for that expansion.
    Signed-off-by: default avatarRobin Holt <holt@sgi.com>
    Signed-off-by: default avatarNate Zimmer <nzimmer@sgi.com>
    Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    Tested-by: default avatarNate Zimmer <nzimmer@sgi.com>
    Tested-by: default avatarWaiman Long <waiman.long@hp.com>
    Tested-by: default avatarDaniel J Blueman <daniel@numascale.com>
    Acked-by: default avatarPekka Enberg <penberg@kernel.org>
    Cc: Robin Holt <robinmholt@gmail.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Waiman Long <waiman.long@hp.com>
    Cc: Scott Norton <scott.norton@hp.com>
    Cc: "Luck, Tony" <tony.luck@intel.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    8e7a7f86
memblock.c 47.7 KB