Messages in this thread Patch in this message | | | From | Uwe Kleine-König <> | Subject | [PATCH RFC] bootmem: micro optimize freeing pages in bulks | Date | Thu, 1 Dec 2011 23:10:55 +0100 |
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The first entry of bdata->node_bootmem_map holds the data for bdata->node_min_pfn up to bdata->node_min_pfn + BITS_PER_LONG - 1. So the test for freeing all pages of a single map entry can be slightly relaxed.
Moreover use DIV_ROUND_UP in another place instead of open coding it.
Cc: Johannes Weiner <hannes@saeurebad.de> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> --- Hello,
I'm not sure the current code is correct (and my patch doesn't fix it):
If
aligned && vec == ~0UL
evalutates to true, but
start + BITS_PER_LONG <= end
does not (or "< end" resp.) the else branch still frees all BITS_PER_LONG pages. Is this intended? If yes, the last check can better be omitted resulting in the pages being freed in a bulk. If not, the loop in the else branch should only do something like:
while (vec && off < min(BITS_PER_LONG, end - start)) { ...
Having said that please note that I just started today to look into mm/ so please take my analysis with a grain of salt.
Best regards Uwe
mm/bootmem.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/bootmem.c b/mm/bootmem.c index fc22150..1e7d791 100644 --- a/mm/bootmem.c +++ b/mm/bootmem.c @@ -56,7 +56,7 @@ early_param("bootmem_debug", bootmem_debug_setup); static unsigned long __init bootmap_bytes(unsigned long pages) { - unsigned long bytes = (pages + 7) / 8; + unsigned long bytes = DIV_ROUND_UP(pages, 8); return ALIGN(bytes, sizeof(long)); } @@ -197,7 +197,7 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata) idx = start - bdata->node_min_pfn; vec = ~map[idx / BITS_PER_LONG]; - if (aligned && vec == ~0UL && start + BITS_PER_LONG < end) { + if (aligned && vec == ~0UL && start + BITS_PER_LONG <= end) { int order = ilog2(BITS_PER_LONG); __free_pages_bootmem(pfn_to_page(start), order); -- 1.7.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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