ocfs2: change default reservation window sizes (b07f8f24) · Commits · 戴 / test

The default reservation size of 4 (32-bit windows) is a bit too ambitious. Scale it back to 16 bits (resv_level=2). I have been testing various sizes on a 4-node cluster which runs a mixed workload that is heavily threaded. With a 256MB local alloc, I get *roughly* the following levels of average file fragmentation: resv_level=0 70% resv_level=1 21% resv_level=2 23% resv_level=3 24% resv_level=4 60% resv_level=5 did not test resv_level=6 60% resv_level=2 seemed like a good compromise between not letting windows be too small, but not so big that heavier workloads will immediately suffer without tuning. This patch also change the behavior of directory reservations - they now track file reservations. The previous compromise of giving directory windows only 8 bits wound up fragmenting more at some window sizes because file allocations had smaller unused windows to poach from. Signed-off-by:

Mark Fasheh <mfasheh@suse.com> Signed-off-by:

Joel Becker <joel.becker@oracle.com>

Documentation/filesystems/ocfs2.txt

+1 −1

Original line number	Diff line number	Diff line
		@@ -80,6 +80,6 @@ user_xattr (*) Enables Extended User Attributes.
		nouser_xattr Disables Extended User Attributes.
		acl Enables POSIX Access Control Lists support.
		noacl (*) Disables POSIX Access Control Lists support.
		resv_level=4 (*) Set how agressive allocation reservations will be.
		resv_level=2 (*) Set how agressive allocation reservations will be.
		Valid values are between 0 (reservations off) to 8
		(maximum space for reservations).

fs/ocfs2/reservations.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -55,9 +55,10 @@ static unsigned int ocfs2_resv_window_bits(struct ocfs2_reservation_map *resmap,
		if (!(resv->r_flags & OCFS2_RESV_FLAG_DIR)) {
		/* 8, 16, 32, 64, 128, 256, 512, 1024 */
		bits = 4 << osb->osb_resv_level;
		} else
		bits = OCFS2_RESV_DIR_WINDOW_BITS;

		} else {
		/* For now, treat directories the same as files. */
		bits = 4 << osb->osb_resv_level;
		}
		return bits;
		}

fs/ocfs2/reservations.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -22,7 +22,7 @@

		#include <linux/rbtree.h>

		#define OCFS2_DEFAULT_RESV_LEVEL 4
		#define OCFS2_DEFAULT_RESV_LEVEL 2
		#define OCFS2_MAX_RESV_LEVEL 9
		#define OCFS2_MIN_RESV_LEVEL 0

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