[root@localhost caq]# xfs_db -c frag -r /dev/sdaw actual 20316, ideal 3544, fragmentation factor 82.56% Note, this number is largely meaningless. Files on this filesystem average 5.73 extents per file [root@localhost caq]# xfs_fsr /dev/sdaw /mnt/K4HUWARB start inode=0 [root@localhost caq]# [root@localhost caq]# [root@localhost caq]# xfs_db -c frag -r /dev/sdaw actual 4159, ideal 3544, fragmentation factor 14.79% Note, this number is largely meaningless. Files on this filesystem average 1.17 extents per file
在碎片化整理之前，碎片化率為82.56%，一般來說，碎片化率高於45%，則建議整理，一來連續的塊可以提高讀的性能，二來可以省出很多block。
除了xfs_fsr,還有很多有用的工具。
xfs_admin xfs_db xfs_freeze xfs_info xfs_logprint xfs_mkfile xfs_repair
xfs_bmap xfsdump xfs_fsr xfsinvutil xfs_mdrestore xfs_ncheck xfsrestore
xfs_copy xfs_estimate xfs_growfs xfs_io xfs_metadump xfs_quota xfs_rtcp
用的最多的是xfs_repair,xfs_check,xfs_db.
xfs_info的使用：
[root@localhost caq]# xfs_info /dev/sdaw meta-data=/dev/sdaw isize=256 agcount=4, agsize=122094720 blks = sectsz=512 attr=2 data = bsize=4096 blocks=488378646, imaxpct=5 = sunit=128 swidth=512 blks naming =version 2 bsize=4096 ascii-ci=0 log =internal bsize=4096 blocks=238472, version=2 = sectsz=512 sunit=8 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0
可以看出，sdaw有4個AG，block個數為 488378646，每個AG管理的block數量為總數量/4, 扇區大小為512，
swidth=0 條帶參數，raid使用。
該掛載點的xfs的日志記錄在內部，有些設備上面既有慢速的機械盤，又有快速的ssd甚至nvme盤，則可以把慢速設備的xfs日志放在nvme上，可以提高性能。
[root@localhost caq]# xfs_info -V xfs_info version 3.1.1
xfs_admin 的使用：
該工具能修改xfs文件系統參數
設置uuid xfs_admin –U uuid /dev/sdc
設置label xfsadmin –L label /dev/sdc
xfs_db工具能打印和修改未mount的，xfs元數據結構體：
xfs_db /dev/sdc
xfs_db> sb
xfs_db> p
magicnum = 0x58465342
blocksize = 4096
dblocks = 524288
修改：xfs_db -x -c 'sb 0' -c 'write dblocks 0' /dev/sdc
查看文件inode xfs_db> inode 131
xfs_db> p
core.magic = 0x494e
core.mode = 0100644
core.version = 2
打印文件系統剩余空間：
xfs_db> freesp from to extents blocks pct 1 1 129 129 0.00 8 15 3 24 0.00 64 127 131 14682 0.00 128 255 35 5613 0.00 256 511 3 892 0.00 512 1023 1 981 0.00 1024 2047 7 10178 0.00 2048 4095 3 8192 0.00 4096 8191 4 24022 0.00 8192 16383 14 176636 0.02 16384 32767 62 1223755 0.13 32768 65535 63 2769390 0.29 65536 131071 67 6069834 0.63 131072 262143 41 7339741 0.76 262144 524287 25 9600697 0.99 524288 1048575 21 14054653 1.46 1048576 2097151 2 2121340 0.22 16777216 30523648 32 922117670 95.50
打印原始16進制數據:
xfs_db> type text
xfs_db> p
00: 49 4e 81 ed 02 02 00 00 00 00 00 00 00 00 00 00 IN..............
10: 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 01 ................
20: 54 a2 14 e5 01 bb 2a 29 54 a2 14 e5 02 72 45 2a T.......T....rE.
30: 54 a2 14 e5 02 72 45 2a 00 00 00 00 00 00 22 4c T....rE........L
40: 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 01 ................
…..
xfs對block的管理是通過分級來管理數據的，扇區，塊，et，ag。
其中：sector<block<extent<ag
typedef struct xfs_agf { /* * Common allocation group header information */ __be32 agf_magicnum; /* magic number == XFS_AGF_MAGIC */ __be32 agf_versionnum; /* header version == XFS_AGF_VERSION */ __be32 agf_seqno; /* sequence # starting from 0 */ __be32 agf_length; /* size in blocks of a.g. */ /* * Freespace information */ __be32 agf_roots[XFS_BTNUM_AGF]; /* root blocks */ __be32 agf_spare0; /* spare field */ __be32 agf_levels[XFS_BTNUM_AGF]; /* btree levels */ __be32 agf_spare1; /* spare field */ __be32 agf_flfirst; /* first freelist block's index */ __be32 agf_fllast; /* last freelist block's index */ __be32 agf_flcount; /* count of blocks in freelist */ __be32 agf_freeblks; /* total free blocks */ __be32 agf_longest; /* longest free space */ __be32 agf_btreeblks; /* # of blocks held in AGF btrees */ uuid_t agf_uuid; /* uuid of filesystem */------------------------------以下字段在2.6.32版本中沒看到，3.10對應的xfs模塊有，中間版本沒對比過 /* * reserve some contiguous space for future logged fields before we add * the unlogged fields. This makes the range logging via flags and * structure offsets much simpler. */ __be64 agf_spare64[16]; /* unlogged fields, written during buffer writeback. */ __be64 agf_lsn; /* last write sequence */ __be32 agf_crc; /* crc of agf sector */ __be32 agf_spare2; /* structure must be padded to 64 bit alignment */ } xfs_agf_t;
可以查看一個agf對比下：
[root@localhost caq]# xfs_db /dev/sdaw xfs_db> agf 0 xfs_db> p magicnum = 0x58414746--------------對比agf_magicnum字段 versionnum = 1---------------------對比agf_versionnum字段 seqno = 0--------------------------對比agf_seqno length = 30523648------------------對比agf_length bnoroot = 144----------------------agf_roots cntroot = 145 bnolevel = 1 cntlevel = 1 flfirst = 0 fllast = 3 flcount = 4 freeblks = 29067437----------------空閑的block數 longest = 28900480-----------------最大的空閑段長度 btreeblks = 0 uuid = 6c46ba7a-03b6-46bc-912c-7bac04aafe92 lsn = 0xd000484b0 crc = 0x37a41d5b (correct)----------crc字段
查看144這個block的信息：
xfs_db> fsblock 144 xfs_db> p 000: 41423342 00000028 ffffffff ffffffff 00000000 00000480 0000000d 000484b0 020: 6c46ba7a 03b646bc 912c7bac 04aafe92 00000000 8e0f24fb 00000004 00000077 040: 00000096 0000006a 000006a4 0000005c 00004107 000002f9 000049a4 0000005c 060: 00006a24 0000005c 00006f24 00001cdc 00008d00 00000100 00015400 00000500 080: 00015b00 00000f00 00016a01 0000007f 0001aa80 00002d00 00021880 00000100 0a0: 00031f80 00003380 00039300 00000500 00041800 00002380 00043b88 00000078 0c0: 0004b704 0000007c 0004f780 00002080 00059800 00000200 00079504 0000037c 0e0: 00081880 00000400 00096180 00000500 0009a680 00000400 000a6a80 00000100 100: 000aab80 00000c00 000ab880 00003400 000b6c80 00000200 000c6e80 00000300 120: 000d7480 00000200 000df088 000000f8 000e3184 0000007c 000f7200 00000f80 140: 00100180 00000200 00118580 00003f80 00164700 00000080 00164880 00003c00 160: 0016c480 00008000 00184480 00004000 0018c480 01b8fc80 0018c480 01b8fc80 180: 0018c480 01b8fc80 0018c480 01b8fc80 0018c480 01b8fc80 001a1e00 01b7a300 1a0: 001a2500 01b79c00 001a2b00 01b79600 001a3100 01b79000 001a3100 01b79000 1c0: 001a3900 01b78800 001a3900 01b78800 001a3b00 01b78600 001a4100 01b78000
這樣打印不明顯，可以跟printf一樣，格式化，
xfs_db> fsblock 144 xfs_db> type bnobt-----------------指定打印的type類型 xfs_db> p magic = 0x41423342-----------------這個可以看到，和上圖直接打印的magic是一樣的，就是‘ABTB’ level = 0--------------------------表示葉子節點，1表示中間節點 numrecs = 40-----------------------本葉子節點管理的空閑block塊，就是recs的數組中有效的元素個數 leftsib = null rightsib = null bno = 1152 lsn = 0xd000484b0 uuid = 6c46ba7a-03b6-46bc-912c-7bac04aafe92 owner = 0 crc = 0x8e0f24fb (correct) recs[1-40] = [startblock,blockcount] 1:[4,119] 2:[150,106] 3:[1700,92] 4:[16647,761] 5:[18852,92] 6:[27172,92] 7:[28452,7388] 8:[36096,256] 9:[87040,1280] 10:[88832,3840] 11:[92673,127] 12:[109184,11520] 13:[137344,256] 14:[204672,13184] 15:[234240,1280] 16:[268288,9088] 17:[277384,120] 18:[308996,124] 19:[325504,8320] 20:[366592,512] 21:[496900,892] 22:[530560,1024] 23:[614784,1280] 24:[632448,1024] 25:[682624,256] 26:[699264,3072] 27:[702592,13312] 28:[748672,512] 29:[814720,768] 30:[881792,512] 31:[913544,248] 32:[930180,124] 33:[1012224,3968] 34:[1048960,512] 35:[1148288,16256] 36:[1459968,128] 37:[1460352,15360] 38:[1492096,32768] 39:[1590400,16384] 40:[1623168,28900480]
查看xfs超級塊的一些信息：
[root@localhost /]# xfs_db /dev/sdaw xfs_db> sb 0-----------------超級塊 xfs_db> p magicnum = 0x58465342--------這個就是XFSB的acsii碼 blocksize = 4096-------------邏輯塊大小 dblocks = 976754646----------磁盤總塊數，塊數*塊大小就是磁盤的空間了 rblocks = 0 rextents = 0 uuid = 6c46ba7a-03b6-46bc-912c-7bac04aafe92 logstart = 536870919 rootino = 1024---------------根節點inode號 rbmino = 1025 rsumino = 1026 rextsize = 1 agblocks = 30523648----------每個AG的塊數量， agcount = 32-----------------32個AG，和AG塊數乘起來就是塊總數 rbmblocks = 0 logblocks = 476930-----------日志塊數 versionnum = 0xbda5 sectsize = 4096 inodesize = 512 inopblock = 8----------------每個block可以存儲的inode的個數，4096/512=8 fname = "\000\000\000\000\000\000\000\000\000\000\000\000"--------------文件系統的名稱 blocklog = 12----------------2的12次方，這個可以和page的shift類比， sectlog = 12-----------------sector大小的log表示， inodelog = 9-----------------inode大小的log表示 inopblog = 3-----------------每個block可以存儲的inode的log表示， agblklog = 25----------------每個ag可以管理的blcok個數的log表示，這個存在向上取整 rextslog = 0 inprogress = 0 imax_pct = 5 icount = 4480 ifree = 929 fdblocks = 931125411 frextents = 0 uquotino = null gquotino = null qflags = 0 flags = 0 shared_vn = 0 inoalignmt = 4 unit = 128 width = 512 dirblklog = 0 logsectlog = 12 logsectsize = 4096 logsunit = 4096 features2 = 0x18a bad_features2 = 0x18a features_compat = 0 features_ro_compat = 0 features_incompat = 0x1 features_log_incompat = 0 crc = 0xd0deb599 (correct) spino_align = 0 pquotino = null lsn = 0xd00048528 meta_uuid = 00000000-0000-0000-0000-000000000000
xfs的加載過程及常見維護的隊列：
Xfs加載ko入口函數在init_xfs_fs，主要申請xfs內核模塊使用的內存資源，注冊xfs文件系統。
常駐內存工作隊列說明：
[xfsalloc] 模塊加載產生，用於文件申請extent的時候，調用__xfs_bmapi_allocate,分配extent。
[xfs_mru_cache] 模塊加載產生，用於訪問MRU (Most Recently Used) Cache的時候使用。
[xfslogd]模塊加載產生，xfs_buf的IO結束調用 b_iodone_work的隊列。
產生階段為mount階段，此時會有指定的實例，掛載點，設備號等。
[xfs-data/sdc]mount產生,數據IO的異步操作隊列，directIO結束的時候調用io_work。
[xfs-conv/sdc] mount產生,數據IO的異步操作隊列，bufIO結束時候調用io_work。
[xfs-cil/sdc] mount產生,push日志的工作隊列，用於xfs_trans_commit將事務提交到日志里。
[xfsaild/sdc] mount產生, xfs_log_worker觸發，將臟節點push到buf，再將buf下盤，umount的時候也經常調用類似流程，如 xfs_ail_push_all_sync 函數。
參考資料：
http://xfs.org/
https://access.redhat.com/
中興OS團隊的相關GPL文檔。