On Tue, Sep 10, 2013 at 01:57:24PM -0500, Nathan Zimmer wrote:
>From: Robin Holt <robin.m.holt@xxxxxxxxx>
>
>On large memory machines it can take a few minutes to get through
>free_all_bootmem().
>
>Currently, when free_all_bootmem() calls __free_pages_memory(), the
>number of contiguous pages that __free_pages_memory() passes to the
>buddy allocator is limited to BITS_PER_LONG. BITS_PER_LONG was originally
>chosen to keep things similar to mm/nobootmem.c. But it is more
>efficient to limit it to MAX_ORDER.
>
> base new change
>8TB 202s 172s 30s
>16TB 401s 351s 50s
>
>That is around 1%-3% improvement on total boot time.
>
>This patch was spun off from the boot time rfc Robin and I had been
>working on.
>
>Signed-off-by: Robin Holt <robin.m.holt@xxxxxxxxx>
>Signed-off-by: Nathan Zimmer <nzimmer@xxxxxxx>
>To: "H. Peter Anvin" <hpa@xxxxxxxxx>
>To: Ingo Molnar <mingo@xxxxxxxxxx>
>Cc: Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>
>Cc: Linux MM <linux-mm@xxxxxxxxx>
>Cc: Rob Landley <rob@xxxxxxxxxxx>
>Cc: Mike Travis <travis@xxxxxxx>
>Cc: Daniel J Blueman <daniel@xxxxxxxxxxxxxxxxxx>
>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
>Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
>Cc: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
>---
> mm/nobootmem.c | 25 ++++++++-----------------
> 1 file changed, 8 insertions(+), 17 deletions(-)
>
>diff --git a/mm/nobootmem.c b/mm/nobootmem.c
>index 61107cf..2c254d3 100644
>--- a/mm/nobootmem.c
>+++ b/mm/nobootmem.c
>@@ -82,27 +82,18 @@ void __init free_bootmem_late(unsigned long addr, unsigned long size)
>
> static void __init __free_pages_memory(unsigned long start, unsigned long end)
> {
>- unsigned long i, start_aligned, end_aligned;
>- int order = ilog2(BITS_PER_LONG);
>+ int order;
>
>- start_aligned = (start + (BITS_PER_LONG - 1)) & ~(BITS_PER_LONG - 1);
>- end_aligned = end & ~(BITS_PER_LONG - 1);
>+ while (start < end) {
>+ order = min(MAX_ORDER - 1UL, __ffs(start));
>
>- if (end_aligned <= start_aligned) {
>- for (i = start; i < end; i++)
>- __free_pages_bootmem(pfn_to_page(i), 0);
>+ while (start + (1UL << order) > end)
>+ order--;
>
>- return;
>- }
>-
>- for (i = start; i < start_aligned; i++)
>- __free_pages_bootmem(pfn_to_page(i), 0);
>+ __free_pages_bootmem(pfn_to_page(start), order);
>
>- for (i = start_aligned; i < end_aligned; i += BITS_PER_LONG)
>- __free_pages_bootmem(pfn_to_page(i), order);
>-
>- for (i = end_aligned; i < end; i++)
>- __free_pages_bootmem(pfn_to_page(i), 0);
>+ start += (1UL << order);
>+ }
> }
>
> static unsigned long __init __free_memory_core(phys_addr_t start,
>--
>1.8.2.1
>
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