blist_alloc_count.patch
dougm (Doug Moore)
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	dougm
	May 2 2019, 3:55 PM

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blist_alloc_count.patch
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	diff --git a/sys/kern/subr_blist.c b/sys/kern/subr_blist.c
	index 3f8f1771d66..f7e431a0513 100644
	--- a/sys/kern/subr_blist.c
	+++ b/sys/kern/subr_blist.c
	@@ -278,6 +278,14 @@ blist_destroy(blist_t bl)
	free(bl, M_SWAP);
	}

	+#include <sys/sysctl.h>
	+static SYSCTL_NODE(_debug, OID_AUTO, counters, CTLFLAG_RD, 0, "");
	+
	+static long alloc_success, alloc_failure, avg_count, count_err;
	+SYSCTL_ULONG(_debug_counters, OID_AUTO, alloc_success, CTLFLAG_RD, &alloc_success, 0, "");
	+SYSCTL_ULONG(_debug_counters, OID_AUTO, alloc_failure, CTLFLAG_RD, &alloc_failure, 0, "");
	+SYSCTL_ULONG(_debug_counters, OID_AUTO, avg_count, CTLFLAG_RD, &avg_count, 0, "");
	+
	/*
	* blist_alloc() - reserve space in the block bitmap. Return the base
	* of a contiguous region or SWAPBLK_NONE if space could
	@@ -297,6 +305,9 @@ blist_alloc(blist_t bl, daddr_t count)
	* non-zero. When the cursor is zero, an allocation failure will
	* stop further iterations.
	*/
	+ count_err += count - avg_count;
	+ avg_count += count_err / (alloc_success + alloc_failure + 1);
	+ count_err %= alloc_success + alloc_failure + 1;
	for (;;) {
	blk = blst_meta_alloc(bl->bl_root, bl->bl_cursor, count,
	bl->bl_radix);
	@@ -305,9 +316,12 @@ blist_alloc(blist_t bl, daddr_t count)
	bl->bl_cursor = blk + count;
	if (bl->bl_cursor == bl->bl_blocks)
	bl->bl_cursor = 0;
	+ alloc_success++;
	return (blk);
	- } else if (bl->bl_cursor == 0)
	+ } else if (bl->bl_cursor == 0) {
	+ alloc_failure++;
	return (SWAPBLK_NONE);
	+ }
	bl->bl_cursor = 0;
	}
	}