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authorDave Chinner <dchinner@redhat.com>2011-01-04 11:35:03 +1100
committerDave Chinner <david@fromorbit.com>2011-01-04 11:35:03 +1100
commit055388a3188f56676c21e92962fc366ac8b5cb72 (patch)
tree57fb9d649956f311031f574e3f6d8f54146f0f2a /fs/xfs/xfs_mount.h
parent622d81494fa32343a4b97b607619656c7a4a6d1a (diff)
xfs: dynamic speculative EOF preallocation
Currently the size of the speculative preallocation during delayed allocation is fixed by either the allocsize mount option of a default size. We are seeing a lot of cases where we need to recommend using the allocsize mount option to prevent fragmentation when buffered writes land in the same AG. Rather than using a fixed preallocation size by default (up to 64k), make it dynamic by basing it on the current inode size. That way the EOF preallocation will increase as the file size increases. Hence for streaming writes we are much more likely to get large preallocations exactly when we need it to reduce fragementation. For default settings, the size of the initial extents is determined by the number of parallel writers and the amount of memory in the machine. For 4GB RAM and 4 concurrent 32GB file writes: EXT: FILE-OFFSET BLOCK-RANGE AG AG-OFFSET TOTAL 0: [0..1048575]: 1048672..2097247 0 (1048672..2097247) 1048576 1: [1048576..2097151]: 5242976..6291551 0 (5242976..6291551) 1048576 2: [2097152..4194303]: 12583008..14680159 0 (12583008..14680159) 2097152 3: [4194304..8388607]: 25165920..29360223 0 (25165920..29360223) 4194304 4: [8388608..16777215]: 58720352..67108959 0 (58720352..67108959) 8388608 5: [16777216..33554423]: 117440584..134217791 0 (117440584..134217791) 16777208 6: [33554424..50331511]: 184549056..201326143 0 (184549056..201326143) 16777088 7: [50331512..67108599]: 251657408..268434495 0 (251657408..268434495) 16777088 and for 16 concurrent 16GB file writes: EXT: FILE-OFFSET BLOCK-RANGE AG AG-OFFSET TOTAL 0: [0..262143]: 2490472..2752615 0 (2490472..2752615) 262144 1: [262144..524287]: 6291560..6553703 0 (6291560..6553703) 262144 2: [524288..1048575]: 13631592..14155879 0 (13631592..14155879) 524288 3: [1048576..2097151]: 30408808..31457383 0 (30408808..31457383) 1048576 4: [2097152..4194303]: 52428904..54526055 0 (52428904..54526055) 2097152 5: [4194304..8388607]: 104857704..109052007 0 (104857704..109052007) 4194304 6: [8388608..16777215]: 209715304..218103911 0 (209715304..218103911) 8388608 7: [16777216..33554423]: 452984848..469762055 0 (452984848..469762055) 16777208 Because it is hard to take back specualtive preallocation, cases where there are large slow growing log files on a nearly full filesystem may cause premature ENOSPC. Hence as the filesystem nears full, the maximum dynamic prealloc size іs reduced according to this table (based on 4k block size): freespace max prealloc size >5% full extent (8GB) 4-5% 2GB (8GB >> 2) 3-4% 1GB (8GB >> 3) 2-3% 512MB (8GB >> 4) 1-2% 256MB (8GB >> 5) <1% 128MB (8GB >> 6) This should reduce the amount of space held in speculative preallocation for such cases. The allocsize mount option turns off the dynamic behaviour and fixes the prealloc size to whatever the mount option specifies. i.e. the behaviour is unchanged. Signed-off-by: Dave Chinner <dchinner@redhat.com>
Diffstat (limited to 'fs/xfs/xfs_mount.h')
-rw-r--r--fs/xfs/xfs_mount.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 5861b498074..a62e8971539 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -103,6 +103,16 @@ extern int xfs_icsb_modify_counters(struct xfs_mount *, xfs_sb_field_t,
xfs_mod_incore_sb(mp, field, delta, rsvd)
#endif
+/* dynamic preallocation free space thresholds, 5% down to 1% */
+enum {
+ XFS_LOWSP_1_PCNT = 0,
+ XFS_LOWSP_2_PCNT,
+ XFS_LOWSP_3_PCNT,
+ XFS_LOWSP_4_PCNT,
+ XFS_LOWSP_5_PCNT,
+ XFS_LOWSP_MAX,
+};
+
typedef struct xfs_mount {
struct super_block *m_super;
xfs_tid_t m_tid; /* next unused tid for fs */
@@ -202,6 +212,8 @@ typedef struct xfs_mount {
__int64_t m_update_flags; /* sb flags we need to update
on the next remount,rw */
struct shrinker m_inode_shrink; /* inode reclaim shrinker */
+ int64_t m_low_space[XFS_LOWSP_MAX];
+ /* low free space thresholds */
} xfs_mount_t;
/*
@@ -379,6 +391,8 @@ extern int xfs_sb_validate_fsb_count(struct xfs_sb *, __uint64_t);
extern int xfs_dev_is_read_only(struct xfs_mount *, char *);
+extern void xfs_set_low_space_thresholds(struct xfs_mount *);
+
#endif /* __KERNEL__ */
extern void xfs_mod_sb(struct xfs_trans *, __int64_t);