[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] xen/common: low performance of lib/sort.c
From: keios <keios.cn@xxxxxxxxx> It is a non-standard heap-sort algorithm implementation because the index of child node is wrong . The sort function still outputs right result, but the performance is O( n * ( log(n) + 1 ) ) , about 10% ~ 20% worse than standard algorithm. Signed-off-by: keios <keios.cn@xxxxxxxxx> [Linux commit: d3717bdf8f08a0e1039158c8bab2c24d20f492b6] Ported to Xen. Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> --- CC: Jan Beulich <JBeulich@xxxxxxxx> --- xen/common/sort.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/xen/common/sort.c b/xen/common/sort.c index d96fc2a..7b7544b 100644 --- a/xen/common/sort.c +++ b/xen/common/sort.c @@ -46,7 +46,7 @@ void sort(void *base, size_t num, size_t size, void (*swap)(void *, void *, int size)) { /* pre-scale counters for performance */ - int i = (num/2) * size, n = num * size, c, r; + int i = (num/2 - 1) * size, n = num * size, c, r; if (!swap) swap = (size == 4 ? u32_swap : generic_swap); @@ -54,9 +54,9 @@ void sort(void *base, size_t num, size_t size, /* heapify */ for ( ; i >= 0; i -= size ) { - for ( r = i; r * 2 < n; r = c ) + for ( r = i; r * 2 + size < n; r = c ) { - c = r * 2; + c = r * 2 + size; if ( (c < n - size) && (cmp(base + c, base + c + size) < 0) ) c += size; if ( cmp(base + r, base + c) >= 0 ) @@ -69,9 +69,9 @@ void sort(void *base, size_t num, size_t size, for ( i = n - size; i >= 0; i -= size ) { swap(base, base + i, size); - for ( r = 0; r * 2 < i; r = c ) + for ( r = 0; r * 2 + size < i; r = c ) { - c = r * 2; + c = r * 2 + size; if ( (c < i - size) && (cmp(base + c, base + c + size) < 0) ) c += size; if ( cmp(base + r, base + c) >= 0 ) -- 2.1.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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