Calculate byte core set for data sample: Sort bucket's numbers in decreasing order Count how many numbers use 90% of sample If core set are low (<=25%), data are easily compressible If core set high (>=80%), data are not compressible
Signed-off-by: Timofey Titovets <[email protected]> --- fs/btrfs/compression.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++ fs/btrfs/compression.h | 2 ++ 2 files changed, 60 insertions(+) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 1429b11f2c5f..a469a7c21f5a 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -33,6 +33,7 @@ #include <linux/bit_spinlock.h> #include <linux/slab.h> #include <linux/sched/mm.h> +#include <linux/sort.h> #include "ctree.h" #include "disk-io.h" #include "transaction.h" @@ -1069,6 +1070,42 @@ static inline int byte_set_size(const struct heuristic_bucket_item *bucket) return byte_set_size; } +/* For bucket sorting */ +static inline int heuristic_bucket_compare(const void *lv, const void *rv) +{ + struct heuristic_bucket_item *l = (struct heuristic_bucket_item *)(lv); + struct heuristic_bucket_item *r = (struct heuristic_bucket_item *)(rv); + + return r->count - l->count; +} + +/* + * Byte Core set size + * How many bytes use 90% of sample + */ +static inline int byte_core_set_size(struct heuristic_bucket_item *bucket, + u32 core_set_threshold) +{ + int a = 0; + u32 coreset_sum = 0; + + for (; a < BTRFS_HEURISTIC_BYTE_CORE_SET_LOW; a++) + coreset_sum += bucket[a].count; + + if (coreset_sum > core_set_threshold) + return a; + + for (; a < BTRFS_HEURISTIC_BYTE_CORE_SET_HIGH; a++) { + if (bucket[a].count == 0) + break; + coreset_sum += bucket[a].count; + if (coreset_sum > core_set_threshold) + break; + } + + return a; +} + /* * Compression heuristic. * @@ -1092,6 +1129,8 @@ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) struct heuristic_bucket_item *bucket; int a, b, ret; u8 symbol, *input_data; + u32 core_set_threshold; + u32 input_size = end - start; ret = 1; @@ -1123,6 +1162,25 @@ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) goto out; } + /* Sort in reverse order */ + sort(bucket, BTRFS_HEURISTIC_BUCKET_SIZE, + sizeof(struct heuristic_bucket_item), &heuristic_bucket_compare, + NULL); + + core_set_threshold = (input_size*90)/(BTRFS_HEURISTIC_ITER_OFFSET*100); + core_set_threshold *= BTRFS_HEURISTIC_READ_SIZE; + + a = byte_core_set_size(bucket, core_set_threshold); + if (a <= BTRFS_HEURISTIC_BYTE_CORE_SET_LOW) { + ret = 2; + goto out; + } + + if (a >= BTRFS_HEURISTIC_BYTE_CORE_SET_HIGH) { + ret = 0; + goto out; + } + out: kfree(bucket); return ret; diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h index 03857967815a..0fcd1a485adb 100644 --- a/fs/btrfs/compression.h +++ b/fs/btrfs/compression.h @@ -139,6 +139,8 @@ struct heuristic_bucket_item { #define BTRFS_HEURISTIC_ITER_OFFSET 256 #define BTRFS_HEURISTIC_BUCKET_SIZE 256 #define BTRFS_HEURISTIC_BYTE_SET_THRESHOLD 64 +#define BTRFS_HEURISTIC_BYTE_CORE_SET_LOW BTRFS_HEURISTIC_BYTE_SET_THRESHOLD +#define BTRFS_HEURISTIC_BYTE_CORE_SET_HIGH 200 // 80% int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end); -- 2.13.3 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
