* How to refresh degraded BTRFS? free space fragmentation, file fragmentation...
@ 2012-12-09 11:12 Martin Steigerwald
2012-12-09 11:20 ` Martin Steigerwald
2013-01-16 20:39 ` Martin Steigerwald
0 siblings, 2 replies; 3+ messages in thread
From: Martin Steigerwald @ 2012-12-09 11:12 UTC (permalink / raw)
To: linux-btrfs
Hi!
I have BTRFS on some systems since more than two years. My experience so
far is: Performance at the beginning is pretty good, but some of my more
often used BTRFS filesystem degrade badly in different areas. On some
workloads pretty quickly.
There are also some fs however that did not degrade that badly. These were
some that have way more free space left than the ones that degraded
badly. About 900 GB freespace left on my eSATA backup disk with BTRFS
that is also quite new. About 80 GB left on my BTRFS RAID 1 local home disk
where I can build debian packages or kernels and such without the restrictions
NFS brings (root squash). These still appear to be fine, but I redid the local
home one with mkfs.btrfs -n 32768 and -l 32768 not to long ago, but I
think it was quite fine before anyway, so I might have overdone it here.
This already points at a way to prevent some degradation BTRFS filesystems:
Leave more free space.
1) fsync speed on my ThinkPad T23 has gone down that much that I use
eatmydata with apt-get dist-upgrade and Co. For that I intend to try out
3.7 kernel as soon as its packaged for Debian Experimental. (And hope
that it resumes nicely again, all kernels since 3.3 didn´t and I do not
really feel like bisecting this.) So I put this aside for now cause it may
not be applicable with most recent kernel. And fsync performance hasn´t
been good in the beginning. I think it degraded, but I am not completely
sure.
2) File fragmentation: Example with a SUSE Manager VirtualBox on an
BTRFS filesystem. The SUSE Manager box received packages for the software
channels and put the metadata inside a PostgreSQL database. A SLES Client
just installed.
filefrag showed fragments to go up quickly to 20000, 30000, 40000 and more.
The performance in the VMs was abysmal. I tried mount -o remount,autodefrag
and then BTRFS got down the fragments to some thousands instead of
ten thousands while raising disk activity quite a lot. The 2,5 inch external
eSATA disk was almost all the time completely in use. But the VM performance
was better. Not nice, but better.
I do not have more exact data right now.
3) Freespace fragmentation on the / filesystem on this ThinkPad T520 with
Intel SSD 320:
=== fstrim ===
merkaba:~> /usr/bin/time fstrim -v /
/: 6849871872 bytes were trimmed
0.00user 5.99system 0:44.69elapsed 13%CPU (0avgtext+0avgdata 752maxresident)k
0inputs+0outputs (0major+237minor)pagefaults 0swaps
It took a second or two in the beginning.
atop:
LVM | rkaba-debian | busy 91% | read 0 | write 10313 | MBw/s 67.48 | avio 0.20 ms |
[…]
DSK | sda | busy 90% | read 0 | write 10319 | MBw/s 67.54 | avio 0.19 ms |
[…]
PID TID RUID THR SYSCPU USRCPU VGROW RGROW RDDSK WRDSK ST EXC S CPUNR CPU CMD 1/2
6085 - root 1 0.29s 0.00s 0K 0K 0K 0K -- - D 0 13% fstrim
10000 write requests in 10 seconds.
vmstat 1:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
3 0 1963688 3943380 156972 1827836 0 0 0 0 5421 15781 6 6 88 0
0 0 1963688 3943132 156972 1827852 0 0 0 0 5733 16478 9 7 83 0
1 0 1963688 3943008 156972 1827992 0 0 0 0 5050 14434 0 4 96 0
1 0 1963688 3949768 156972 1826708 0 0 0 0 5246 14960 2 5 93 0
0 0 1963688 3949644 156980 1826712 0 0 0 36 5104 14996 1 4 94 0
0 0 1963688 3949768 156980 1826720 0 0 0 0 5102 15210 2 4 94 0
3 0 1963688 3949644 156980 1826720 0 0 0 0 5321 15995 4 7 89 0
0 0 1963688 3949396 156980 1827188 0 0 0 0 5316 15616 6 5 88 0
1 0 1963688 3949148 156980 1827188 0 0 0 0 5102 14944 1 4 95 0
1 0 1963688 3949272 156980 1827188 0 0 0 0 5510 15928 5 6 89 0
1 0 1963688 3949272 156980 1827188 0 0 0 52 5107 15054 2 4 94 0
0 0 1963688 3949396 156980 1826868 0 0 0 4 4930 14567 1 4 95 0
1 0 1963688 3949396 156988 1826828 0 0 0 52 5132 15014 2 5 93 0
3 0 1963688 3949396 156988 1826836 0 0 0 0 5015 14447 1 4 95 0
0 0 1963688 3949520 156988 1826836 0 0 0 0 5233 15652 3 6 91 0
1 0 1963684 3949612 156988 1827172 0 0 0 3032 2546 7555 6 4 84 6
After fstrim:
0 0 1963684 3944244 157016 1827752 0 0 0 0 357 1018 2 1 97 0
1 0 1963684 3943776 157024 1827776 0 0 0 64 634 1660 4 2 93 0
0 0 1963684 3943872 157024 1827784 0 0 0 0 180 473 0 0 99 0
The I/O activity does not seem to be reflected in vmstat, I bet due to page
cache not involved.
=== fallocate ===
merkaba:/var/tmp> /usr/bin/time fallocate -l 2G fallocate-test
0.00user 118.85system 2:00.50elapsed 98%CPU (0avgtext+0avgdata 720maxresident)k
14912inputs+49112outputs (0major+227minor)pagefaults 0swaps
Peaks or CPU usage:
cpu | sys 98% | user 0% | irq 0% | idle 0% | cpu002 w 2% | avgscal 100% |
CPU | sys 102% | user 3% | irq 0% | idle 295% | wait 1% | avgscal 52% |
cpu | sys 46% | user 1% | irq 0% | idle 53% | cpu001 w 0% | avgscal 63% |
cpu | sys 29% | user 1% | irq 0% | idle 70% | cpu003 w 0% | avgscal 57% |
cpu | sys 26% | user 1% | irq 0% | idle 73% | cpu002 w 0% | avgscal 55% |
cpu | sys 1% | user 1% | irq 0% | idle 99% | cpu000 w 0% | avgscal 32% |
PID TID RUID THR SYSCPU USRCPU VGROW RGROW RDDSK WRDSK ST EXC S CPUNR CPU CMD 1/3
6458 - root 0 2m00s 0.00s 0K 0K - - NE 0 E - 100% <fallocate>
martin@merkaba:~> vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
0 0 1963676 3949112 157168 1827504 14 30 137 47 93 28 11 5 83 0
0 0 1963676 3943148 157168 1828228 0 0 0 0 508 1177 4 2 94 0
1 0 1963676 3943088 157168 1828164 0 0 0 0 584 1381 4 2 94 0
0 0 1963676 3942892 157168 1828164 0 0 0 0 712 1627 6 3 91 0
1 0 1963676 3942508 157168 1828420 0 0 168 0 1252 1432 0 17 82 0
1 0 1963676 3941800 157168 1829012 0 0 136 0 1661 1700 1 26 73 0
1 0 1963676 3940980 157176 1829796 0 0 172 44 1800 1842 1 25 74 0
1 0 1963676 3941088 157176 1829656 0 0 92 0 1701 1101 0 25 75 0
1 0 1963676 3945848 157176 1830092 0 0 140 0 1715 1300 0 25 75 0
1 0 1963676 3945848 157176 1829912 0 0 76 0 1506 1163 0 25 75 0
1 0 1963676 3939168 157176 1831120 0 0 40 0 1840 1164 1 25 74 0
1 0 1963676 3938528 157176 1831440 0 0 172 0 1652 1617 1 25 74 0
1 0 1963676 3939056 157176 1831224 0 0 44 48 1698 1798 1 27 73 0
1 0 1963676 3944452 157176 1831264 0 0 104 0 1383 1106 1 25 74 0
2 0 1963676 3944064 157176 1831644 0 0 88 0 1597 1301 1 26 74 0
1 0 1963676 3943816 157176 1831832 0 0 64 0 1572 1179 1 26 74 0
1 0 1963676 3943304 157176 1832232 0 0 148 0 2009 2600 1 25 74 0
1 0 1963676 3942932 157176 1832752 0 0 8 0 1917 2300 1 26 73 0
2 0 1963668 3942932 157184 1832816 0 0 36 148 1885 2269 2 26 72 0
1 0 1963668 3942428 157184 1833076 0 0 136 0 2063 2823 1 26 73 0
2 0 1963668 3942172 157184 1833628 0 0 84 0 2037 3236 4 26 69 0
1 0 1963668 3941924 157184 1833692 0 0 56 0 1982 2167 1 26 73 0
2 0 1963668 3927648 157184 1835672 0 0 124 0 2214 2734 6 26 68 0
1 0 1963668 3927648 157184 1835756 0 0 80 72 1638 1668 1 25 74 0
Filesystem type is: 9123683e
File size of fallocate-test is 2147483648 (524288 blocks, blocksize 4096)
ext logical physical expected length flags
0 0 2626450 2048
1 2048 3215128 2628498 2040
2 4088 3408631 3217168 2032
3 6120 3430045 3410663 2024
4 8144 3439999 3432069 2016
5 10160 3474610 3442015 1004
6 11164 3743715 3475614 1002
7 12166 2108412 3744717 1000
8 13166 2943991 2109412 998
9 14164 3107711 2944989 996
10 15160 3217168 3108707 994
11 16154 3324557 3218162 496
12 16650 3349504 3325053 495
13 17145 3350737 3349999 495
14 17640 3352158 3351232 494
15 18134 3355223 3352652 494
16 18628 3359558 3355717 493
17 19121 3367645 3360051 493
18 19614 3369156 3368138 492
19 20106 3382494 3369648 492
20 20598 3383027 3382986 491
21 21089 3385838 3383518 491
22 21580 3442449 3386329 490
23 22070 3470434 3442939 490
24 22560 3500244 3470924 489
25 23049 3532609 3500733 489
26 23538 3559176 3533098 489
27 24027 3561437 3559665 488
28 24515 3565004 3561925 488
29 25003 3569963 3565492 487
30 25490 3573446 3570450 487
31 25977 3735991 3573933 486
32 26463 3745098 3736477 486
33 26949 3901106 3745584 485
34 27434 3901681 3901591 485
35 27919 956052 3902166 484
36 28403 984140 956536 484
37 28887 1017986 984624 483
38 29370 1032244 1018469 483
39 29853 1478810 1032727 482
40 30335 1479480 1479292 482
41 30817 1480016 1479962 481
42 31298 1512813 1480497 481
43 31779 1515627 1513294 480
44 32259 1759660 1516107 480
45 32739 1866977 1760140 480
46 33219 2025589 1867457 479
47 33698 2044003 2026068 479
48 34177 2233664 2044482 478
49 34655 2246706 2234142 478
50 35133 2336760 2247184 477
51 35610 2348377 2337237 477
52 36087 2396156 2348854 476
53 36563 2453672 2396632 476
54 37039 2505829 2454148 475
55 37514 2559971 2506304 475
56 37989 2568049 2560446 474
57 38463 2569417 2568523 474
58 38937 2575922 2569891 473
59 39410 2578488 2576395 473
60 39883 2989056 2578961 946
61 40829 2995464 2990002 472
62 41301 3197446 2995936 471
63 41772 3206085 3197917 471
64 42243 3467053 3206556 470
65 42713 2579027 3467523 470
66 43183 2727531 2579497 469
67 43652 2729381 2728000 469
68 44121 2730137 2729850 468
69 44589 2875164 2730605 468
70 45057 2902010 2875632 467
71 45524 2917719 2902477 467
72 45991 2920037 2918186 467
73 46458 2930483 2920504 466
74 46924 2931689 2930949 466
75 47390 2941544 2932155 465
76 47855 2943422 2942009 465
77 48320 2955072 2943887 464
78 48784 2962691 2955536 464
79 49248 2964241 2963155 463
80 49711 2965864 2964704 463
81 50174 2979347 2966327 463
82 50637 2985719 2979810 462
83 51099 3033228 2986181 462
84 51561 4096111 3033690 461
85 52022 2913433 4096572 461
86 52483 2914231 2913894 230
87 52713 2915298 2914461 230
88 52943 2917405 2915528 230
89 53173 2918359 2917635 230
90 53403 2087430 2918589 459
91 53862 2109512 2087889 229
92 54091 2110584 2109741 229
93 54320 2111695 2110813 229
94 54549 2157184 2111924 229
95 54778 2158300 2157413 229
96 55007 2165613 2158529 229
97 55236 2167222 2165842 229
98 55465 2196837 2167451 228
99 55693 2199378 2197065 228
[…]
306 106611 1243376 1168146 203
307 106814 1245114 1243579 203
308 107017 1294949 1245317 203
309 107220 1408543 1295152 203
310 107423 1408788 1408746 203
311 107626 1448445 1408991 203
312 107829 1451116 1448648 203
313 108032 1453560 1451319 203
314 108235 1459015 1453763 203
315 108438 1460375 1459218 203
316 108641 1461372 1460578 202
317 108843 1471758 1461574 202
[…]
4526 522694 2939615 3455932 49
4527 522743 2517410 2939664 48
4528 522791 2460124 2517458 46
4529 522837 2458204 2460170 45
4530 522882 2479853 2458249 43
4531 522925 1687125 2479896 42
4532 522967 646064 1687167 41
4533 523008 497470 646105 40
4534 523048 4111482 497510 77
4535 523125 4097378 4111559 72
4536 523197 3949964 4097450 68
4537 523265 3499481 3950032 63
4538 523328 3499660 3499544 60
4539 523388 3495885 3499720 56
4540 523444 3498714 3495941 52
4541 523496 2960575 3498766 49
4542 523545 2482351 2960624 46
4543 523591 2481927 2482397 43
4544 523634 532779 2481970 40
4545 523674 4170769 532819 76
4546 523750 3935305 4170845 67
4547 523817 3498776 3935372 58
4548 523875 3502955 3498834 51
4549 523926 2489644 3503006 45
4550 523971 338996 2489689 39
4551 524010 4035101 339035 69
4552 524079 3506596 4035170 52
4553 524131 399363 3506648 39
4554 524170 3550735 399402 59
4555 524229 3553226 3550794 59 eof
fallocate-test: 4556 extents found
But:
merkaba:/var/tmp> /usr/bin/time rm fallocate-test
0.00user 0.24system 0:00.38elapsed 63%CPU (0avgtext+0avgdata 784maxresident)k
4464inputs+36184outputs (0major+243minor)pagefaults 0swaps
Some more information on the filesystem in question:
merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs fi sh
failed to read /dev/sr0
Label: 'debian' uuid: […]
Total devices 1 FS bytes used 13.56GB
devid 1 size 18.62GB used 18.62GB path /dev/dm-0
Btrfs v0.19-239-g0155e84
merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs fi df /
Disk size: 18.62GB
Disk allocated: 18.62GB
Disk unallocated: 0.00
Used: 13.56GB
Free (Estimated): 3.31GB (Max: 3.31GB, min: 3.31GB)
Data to disk ratio: 91 %
merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs fi disk-usage /
Data,Single: Size:15.10GB, Used:12.94GB
/dev/dm-0 15.10GB
Metadata,Single: Size:8.00MB, Used:0.00
/dev/dm-0 8.00MB
Metadata,DUP: Size:1.75GB, Used:630.11MB
/dev/dm-0 3.50GB
System,Single: Size:4.00MB, Used:0.00
/dev/dm-0 4.00MB
System,DUP: Size:8.00MB, Used:4.00KB
/dev/dm-0 16.00MB
Unallocated:
/dev/dm-0 0.00
merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs dev disk-usage /
/dev/dm-0 18.62GB
Data,Single: 15.10GB
Metadata,Single: 8.00MB
Metadata,DUP: 3.50GB
System,Single: 4.00MB
System,DUP: 16.00MB
Unallocated: 0.00
Compared to that an Ext4 in /home on the SSD that is almost full doesn´t
show much signs aging degradation yet inspite being quite full and nepomuk
trashes it quite good at times (virtuoso database):
merkaba:/home> /usr/bin/time fallocate -l 2G fallocate-test
0.00user 0.01system 0:00.01elapsed 100%CPU (0avgtext+0avgdata 720maxresident)k
0inputs+0outputs (0major+229minor)pagefaults 0swaps
(without FL_NO_HIDE_STALE stuff of course :)
merkaba:/home> filefrag -v fallocate-test
Filesystem type is: ef53
File size of fallocate-test is 2147483648 (524288 blocks, blocksize 4096)
ext logical physical expected length flags
0 0 22091776 2048 unwritten
1 2048 22102016 22093824 2048 unwritten
2 4096 22149120 22104064 2048 unwritten
3 6144 22224896 22151168 2048 unwritten
4 8192 22261760 22226944 2048 unwritten
5 10240 22274048 22263808 2048 unwritten
6 12288 22278144 22276096 4096 unwritten
7 16384 22292480 22282240 2048 unwritten
8 18432 22306816 22294528 8192 unwritten
9 26624 22355968 22315008 4096 unwritten
10 30720 22411264 22360064 2048 unwritten
11 32768 22425600 22413312 4096 unwritten
12 36864 22476800 22429696 2048 unwritten
13 38912 22577152 22478848 2048 unwritten
14 40960 22603776 22579200 2048 unwritten
15 43008 22607872 22605824 2048 unwritten
16 45056 22620160 22609920 2048 unwritten
17 47104 22614016 22622208 4096 unwritten
18 51200 22646784 22618112 2048 unwritten
19 53248 22697984 22648832 2048 unwritten
20 55296 22738944 22700032 2048 unwritten
21 57344 22769664 22740992 4096 unwritten
22 61440 22775808 22773760 6144 unwritten
23 67584 22818816 22781952 4096 unwritten
24 71680 22867968 22822912 4096 unwritten
25 75776 22896640 22872064 8192 unwritten
[…]
150 483328 29599744 29501440 2048 unwritten
151 485376 29632512 29601792 2048 unwritten
152 487424 29646848 29634560 8192 unwritten
153 495616 29669376 29655040 10240 unwritten
154 505856 29685760 29679616 2048 unwritten
155 507904 29691904 29687808 2048 unwritten
156 509952 29696000 29693952 2048 unwritten
157 512000 29700096 29698048 2048 unwritten
158 514048 29712384 29702144 2048 unwritten
159 516096 29718528 29714432 2048 unwritten
160 518144 29736960 29720576 2048 unwritten
161 520192 29743104 29739008 2048 unwritten
162 522240 29767680 29745152 2048 unwritten,eof
fallocate-test: 163 extents found
merkaba:/home> /usr/bin/time rm fallocate-test
0.00user 0.00system 0:00.00elapsed 100%CPU (0avgtext+0avgdata 784maxresident)k
0inputs+0outputs (0major+244minor)pagefaults 0swaps
merkaba:~> LANG=C df -hT /home
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/merkaba-home ext4 221G 209G 8.8G 96% /home
I know this is still twice as much free space than with the BTRFS volume.
And a different workload. And the BTRFS filesystem has been a bit fuller
at times. I just do not have two filesystems that degrade by exactly the
same workload at hand.
merkaba:~> e2freefrag /dev/merkaba/home
Device: /dev/merkaba/home
Blocksize: 4096 bytes
Total blocks: 58593280
Free blocks: 2921471 (5.0%)
Min. free extent: 4 KB
Max. free extent: 57344 KB
Avg. free extent: 224 KB
Num. free extent: 51323
HISTOGRAM OF FREE EXTENT SIZES:
Extent Size Range : Free extents Free Blocks Percent
4K... 8K- : 12118 12118 0.41%
8K... 16K- : 13221 29823 1.02%
16K... 32K- : 8431 42289 1.45%
32K... 64K- : 5952 63186 2.16%
64K... 128K- : 3657 80646 2.76%
128K... 256K- : 2483 109538 3.75%
256K... 512K- : 1740 154664 5.29%
512K... 1024K- : 1404 255117 8.73%
1M... 2M- : 1302 468132 16.02%
2M... 4M- : 487 335516 11.48%
4M... 8M- : 255 357015 12.22%
8M... 16M- : 182 455025 15.58%
16M... 32M- : 76 385687 13.20%
32M... 64M- : 15 140176 4.80%
merkaba:/home> e4defrag -c /home
<Fragmented files> now/best size/ext
1. /home/martin/Mail/[… some kmail index …]
7/1 4 KB
2. /home/martin/Mail/[… some kmail index …]
4/1 4 KB
3. /home/martin/[…]/.bzr/checkout/dirstate
4/1 4 KB
4. /home/martin/[… some small kexi database …].kexi
6/1 4 KB
5. /home/martin/.kde/share/apps/kraft/sqlite/kraft.db
15/1 5 KB
Total/best extents 926792/904756
Average size per extent 238 KB
Fragmentation score 0
[0-30 no problem: 31-55 a little bit fragmented: 56- needs defrag]
This directory (/home) does not need defragmentation.
Done.
My questions now are:
a) Are there other ways a BTRFS filesystem can degrade?
b) How to diagnose degradation of BTRFS? How to diagnose which kind of
aging slows down a given BTRFS filesystem?
- some tool to measure free space fragmentation like e2freefrag (see
above)?
- some tool to measure file fragmentation like e4defrag -c (see above)?
I think there might be some of this already?
- btrfs-calc-size for tree diagnosing?
merkaba:~> btrfs-calc-size /dev/merkaba/debian
Calculating size of root tree
16.00KB total size, 0.00 inline data, 1 nodes, 3 leaves, 2 levels
Calculating size of extent tree
53.66MB total size, 0.00 inline data, 222 nodes, 13515 leaves, 4 levels
Calculating size of csum tree
19.58MB total size, 0.00 inline data, 76 nodes, 4936 leaves, 3 levels
Calculatin' size of fs tree
554.04MB total size, 198.86MB inline data, 2142 nodes, 139693 leaves, 4 levels
Levels seem sane to me.
- btrfs-debug-tree? But thats too much output for a regular admin I think.
b) What do to about it?
While I understand that the fragmentation issues are quite deeply related
to the copy on write nature of BTRFS they are still an issue. Even on SSDs
as I showed above.
Granted boot speed of the filesystem and creating small files are still fast
enough on the SSD. The SSD seems to compensate over that fragmentation
quite well.
But still is there anything that can be done?
i) By enhancing BTRFS?
- insert your suggestion here
ii) By some admin tasks or filesystem maintenance? Are the safe ones that
do really improve the FS layout instead of making it worse? Once I tried
btrfs filesystem balance on the root filesystem mentioned above, and the
net result was, that boot speed doubled according to systemd-analyze.
- maybe (still) some btrfs filesystem balance run?
- maybe some btrfs filesystem defragment runs? By a script recursively,
as long as thats not implemented within btrfs command itself. I would
prefer that (along the lines of e4defrag also with option -c to first
diagnose whether defragmentation does make sense]
What kinds of degradation are important to performance and which ones
are not?
iii) And what can be done to prevent degradation?
- leave more free space, maybe lots more free space?
I then just reformatted the volume and never tried a balance again so far.
But I am ready to try suggestions on this FS, as I plan to redo it with
mkfs.btrfs -l 16384 -n 16384 (big metadata) anyway.
I think this will be questions admins will have when first production
BTRFS filesystem start to degrade. And I thought it might be a good idea to
think about good answers to them.
Feel free to split out the thread by changing subject lines into free space
fragmentation, file fragmentation ... where it makes sense.
Thanks,
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: How to refresh degraded BTRFS? free space fragmentation, file fragmentation...
2012-12-09 11:12 How to refresh degraded BTRFS? free space fragmentation, file fragmentation Martin Steigerwald
@ 2012-12-09 11:20 ` Martin Steigerwald
2013-01-16 20:39 ` Martin Steigerwald
1 sibling, 0 replies; 3+ messages in thread
From: Martin Steigerwald @ 2012-12-09 11:20 UTC (permalink / raw)
To: linux-btrfs
Am Sonntag, 9. Dezember 2012 schrieb Martin Steigerwald:
> Hi!
>
> I have BTRFS on some systems since more than two years. My experience so
> far is: Performance at the beginning is pretty good, but some of my more
> often used BTRFS filesystem degrade badly in different areas. On some
> workloads pretty quickly.
>
> There are also some fs however that did not degrade that badly. These were
> some that have way more free space left than the ones that degraded
> badly. About 900 GB freespace left on my eSATA backup disk with BTRFS
> that is also quite new. About 80 GB left on my BTRFS RAID 1 local home disk
> where I can build debian packages or kernels and such without the restrictions
> NFS brings (root squash). These still appear to be fine, but I redid the local
> home one with mkfs.btrfs -n 32768 and -l 32768 not to long ago, but I
> think it was quite fine before anyway, so I might have overdone it here.
> This already points at a way to prevent some degradation BTRFS filesystems:
> Leave more free space.
I also do not use them regularily as in each day.
Backup disk just every two weeks or so.
Local home sometimes each day a week, then not at all for weeks.
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: How to refresh degraded BTRFS? free space fragmentation, file fragmentation...
2012-12-09 11:12 How to refresh degraded BTRFS? free space fragmentation, file fragmentation Martin Steigerwald
2012-12-09 11:20 ` Martin Steigerwald
@ 2013-01-16 20:39 ` Martin Steigerwald
1 sibling, 0 replies; 3+ messages in thread
From: Martin Steigerwald @ 2013-01-16 20:39 UTC (permalink / raw)
To: linux-btrfs
Am Sonntag, 9. Dezember 2012 schrieb Martin Steigerwald:
> Hi!
>
> I have BTRFS on some systems since more than two years. My experience so
> far is: Performance at the beginning is pretty good, but some of my more
> often used BTRFS filesystem degrade badly in different areas. On some
> workloads pretty quickly.
>
> There are also some fs however that did not degrade that badly. These were
> some that have way more free space left than the ones that degraded
> badly. About 900 GB freespace left on my eSATA backup disk with BTRFS
> that is also quite new. About 80 GB left on my BTRFS RAID 1 local home disk
> where I can build debian packages or kernels and such without the restrictions
> NFS brings (root squash). These still appear to be fine, but I redid the local
> home one with mkfs.btrfs -n 32768 and -l 32768 not to long ago, but I
> think it was quite fine before anyway, so I might have overdone it here.
> This already points at a way to prevent some degradation BTRFS filesystems:
> Leave more free space.
>
>
> 1) fsync speed on my ThinkPad T23 has gone down that much that I use
[…]
Interesting to try after latest fsync improvements.
> 2) File fragmentation: Example with a SUSE Manager VirtualBox on an
[…]
> 3) Freespace fragmentation on the / filesystem on this ThinkPad T520 with
> Intel SSD 320:
>
> === fstrim ===
>
> merkaba:~> /usr/bin/time fstrim -v /
> /: 6849871872 bytes were trimmed
> 0.00user 5.99system 0:44.69elapsed 13%CPU (0avgtext+0avgdata 752maxresident)k
> 0inputs+0outputs (0major+237minor)pagefaults 0swaps
>
> It took a second or two in the beginning.
>
>
> atop:
>
> LVM | rkaba-debian | busy 91% | read 0 | write 10313 | MBw/s 67.48 | avio 0.20 ms |
> […]
> DSK | sda | busy 90% | read 0 | write 10319 | MBw/s 67.54 | avio 0.19 ms |
> […]
>
> PID TID RUID THR SYSCPU USRCPU VGROW RGROW RDDSK WRDSK ST EXC S CPUNR CPU CMD 1/2
> 6085 - root 1 0.29s 0.00s 0K 0K 0K 0K -- - D 0 13% fstrim
>
>
> 10000 write requests in 10 seconds.
I was able to refresh my BTRFS regarding this issue on 11th of January:
merkaba:~> btrfs filesystem df /
Data: total=15.10GB, used=11.06GB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.75GB, used=654.12MB
Metadata: total=8.00MB, used=0.00
merkaba:~> btrfs balance start -dusage=5 /
Done, had to relocate 0 out of 25 chunks
merkaba:~> btrfs filesystem df /
Data: total=15.01GB, used=11.06GB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.75GB, used=654.05MB
Metadata: total=8.00MB, used=0.00
merkaba:~> btrfs balance start -d /
Done, had to relocate 16 out of 25 chunks
merkaba:~> btrfs filesystem df /
Data: total=11.09GB, used=11.06GB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.75GB, used=647.72MB
Metadata: total=8.00MB, used=0.00
merkaba:~> /usr/bin/time -v fstrim -v /
/: 2246623232 bytes were trimmed
Command being timed: "fstrim -v /"
User time (seconds): 0.00
System time (seconds): 2.34
Percent of CPU this job got: 10%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:21.84
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 748
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 239
Voluntary context switches: 110690
Involuntary context switches: 1426
Swaps: 0
File system inputs: 16
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
merkaba:~> btrfs balance start -fmconvert=single /
Done, had to relocate 8 out of 20 chunks
merkaba:~> btrfs filesystem df /
Data: total=11.09GB, used=11.06GB
System: total=36.00MB, used=4.00KB
Metadata: total=1.75GB, used=642.92MB
[406005.831307] btrfs: balance will reduce metadata integrity, use force if you want this
[406129.187057] btrfs: force reducing metadata integrity
[406129.199133] btrfs: relocating block group 9290383360 flags 36
[406132.645299] btrfs: found 6989 extents
[406132.673390] btrfs: relocating block group 8082423808 flags 36
[406135.807065] btrfs: found 6906 extents
[406135.841572] btrfs: relocating block group 7948206080 flags 36
[406138.413270] btrfs: found 4514 extents
[406138.435382] btrfs: relocating block group 6740246528 flags 36
[406142.572004] btrfs: found 10667 extents
[406142.638079] btrfs: relocating block group 6606028800 flags 36
[406146.272095] btrfs: found 19844 extents
[406146.289729] btrfs: relocating block group 6471811072 flags 36
[406149.136422] btrfs: found 14850 extents
[406149.159510] btrfs: relocating block group 29360128 flags 36
[406183.637010] btrfs: found 116645 extents
[406183.653225] btrfs: relocating block group 20971520 flags 34
[406183.671958] btrfs: found 1 extents
Metadata tree still on old size, thus a regular rebalance:
merkaba:~> btrfs balance start -m /
Done, had to relocate 8 out of 20 chunks
merkaba:~> btrfs filesystem df /
Data: total=11.09GB, used=11.06GB
System: total=36.00MB, used=4.00KB
Metadata: total=768.00MB, used=643.38MB
[406270.880962] btrfs: relocating block group 31801212928 flags 2
[406270.961955] btrfs: found 1 extents
[406270.976857] btrfs: relocating block group 31532777472 flags 4
[406270.990729] btrfs: relocating block group 31264342016 flags 4
[406271.006172] btrfs: relocating block group 30995906560 flags 4
[406271.020158] btrfs: relocating block group 30727471104 flags 4
[406271.480442] btrfs: found 5187 extents
[406271.515768] btrfs: relocating block group 30459035648 flags 4
[406277.158280] btrfs: found 54593 extents
[406277.173024] btrfs: relocating block group 30190600192 flags 4
[406284.680294] btrfs: found 63749 extents
[406284.756582] btrfs: relocating block group 29922164736 flags 4
[406290.907101] btrfs: found 59530 extents
merkaba:~> df -hT /
Dateisystem Typ Größe Benutzt Verf. Verw% Eingehängt auf
/dev/dm-0 btrfs 19G 12G 6,8G 64% /
merkaba:~> /usr/bin/time -v fstrim -v /
/: 5472256 bytes were trimmed
Command being timed: "fstrim -v /"
User time (seconds): 0.00
System time (seconds): 0.00
Percent of CPU this job got: 50%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.00
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 748
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 238
Voluntary context switches: 12
Involuntary context switches: 3
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
Today Still fast:
merkaba:~#1> /usr/bin/time -v fstrim /
Command being timed: "fstrim /"
User time (seconds): 0.00
System time (seconds): 0.03
Percent of CPU this job got: 17%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.19
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 708
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 227
Voluntary context switches: 736
Involuntary context switches: 35
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
Boot time seems a tad bid slower tough:
merkaba:~> systemd-analyze
Startup finished in 5495ms (kernel) + 6331ms (userspace) = 11827ms
merkaba:~> systemd-analyze blame
3051ms cups.service
2330ms dirmngr.service
2267ms postfix.service
1411ms schroot.service
1385ms lvm2.service
1230ms network-manager.service
1128ms ssh.service
1117ms acpi-fakekey.service
1112ms avahi-daemon.service
1061ms privoxy.service
1010ms systemd-logind.service
721ms loadcpufreq.service
646ms colord.service
552ms kdm.service
533ms networking.service
532ms keyboard-setup.service
463ms remount-rootfs.service
368ms bootlogs.service
349ms udev.service
327ms console-kit-log-system-start.service
326ms postgresql.service
322ms binfmt-support.service
316ms acpi-support.service
315ms qemu-kvm.service
310ms sys-kernel-debug.mount
309ms dev-mqueue.mount
309ms anacron.service
303ms atd.service
297ms sys-kernel-security.mount
282ms cron.service
282ms dev-hugepages.mount
272ms lightdm.service
271ms console-kit-daemon.service
271ms lirc.service
268ms lxc.service
259ms cpufrequtils.service
259ms mdadm.service
252ms openntpd.service
240ms smartmontools.service
240ms alsa-utils.service
237ms run-user.mount
237ms speech-dispatcher.service
230ms udftools.service
229ms run-lock.mount
229ms systemd-remount-api-vfs.service
224ms ebtables.service
214ms openbsd-inetd.service
208ms motd.service
199ms hdparm.service
198ms irqbalance.service
190ms mountdebugfs.service
181ms saned.service
160ms systemd-user-sessions.service
157ms polkitd.service
147ms screen-cleanup.service
146ms console-setup.service
141ms networking-routes.service
140ms pppd-dns.service
130ms rc.local.service
130ms jove.service
128ms sysstat.service
112ms rsyslog.service
111ms udev-trigger.service
103ms home.mount
93ms systemd-sysctl.service
89ms boot.mount
85ms dns-clean.service
84ms kbd.service
66ms upower.service
60ms systemd-tmpfiles-setup.service
53ms openvpn.service
37ms boot-efi.mount
27ms udisks.service
22ms sysfsutils.service
22ms mdadm-raid.service
20ms proc-sys-fs-binfmt_misc.mount
18ms tmp.mount
2ms sys-fs-fuse-connections.mount
> vmstat 1:
>
> procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 3 0 1963688 3943380 156972 1827836 0 0 0 0 5421 15781 6 6 88 0
> 0 0 1963688 3943132 156972 1827852 0 0 0 0 5733 16478 9 7 83 0
> 1 0 1963688 3943008 156972 1827992 0 0 0 0 5050 14434 0 4 96 0
> 1 0 1963688 3949768 156972 1826708 0 0 0 0 5246 14960 2 5 93 0
> 0 0 1963688 3949644 156980 1826712 0 0 0 36 5104 14996 1 4 94 0
> 0 0 1963688 3949768 156980 1826720 0 0 0 0 5102 15210 2 4 94 0
> 3 0 1963688 3949644 156980 1826720 0 0 0 0 5321 15995 4 7 89 0
> 0 0 1963688 3949396 156980 1827188 0 0 0 0 5316 15616 6 5 88 0
> 1 0 1963688 3949148 156980 1827188 0 0 0 0 5102 14944 1 4 95 0
> 1 0 1963688 3949272 156980 1827188 0 0 0 0 5510 15928 5 6 89 0
> 1 0 1963688 3949272 156980 1827188 0 0 0 52 5107 15054 2 4 94 0
> 0 0 1963688 3949396 156980 1826868 0 0 0 4 4930 14567 1 4 95 0
> 1 0 1963688 3949396 156988 1826828 0 0 0 52 5132 15014 2 5 93 0
> 3 0 1963688 3949396 156988 1826836 0 0 0 0 5015 14447 1 4 95 0
> 0 0 1963688 3949520 156988 1826836 0 0 0 0 5233 15652 3 6 91 0
> 1 0 1963684 3949612 156988 1827172 0 0 0 3032 2546 7555 6 4 84 6
>
> After fstrim:
>
> 0 0 1963684 3944244 157016 1827752 0 0 0 0 357 1018 2 1 97 0
> 1 0 1963684 3943776 157024 1827776 0 0 0 64 634 1660 4 2 93 0
> 0 0 1963684 3943872 157024 1827784 0 0 0 0 180 473 0 0 99 0
>
>
> The I/O activity does not seem to be reflected in vmstat, I bet due to page
> cache not involved.
> === fallocate ===
>
> merkaba:/var/tmp> /usr/bin/time fallocate -l 2G fallocate-test
> 0.00user 118.85system 2:00.50elapsed 98%CPU (0avgtext+0avgdata 720maxresident)k
> 14912inputs+49112outputs (0major+227minor)pagefaults 0swaps
Now, lets try this:
merkaba:/var/tmp> /usr/bin/time -v fallocate -l 2G fallocate-test
Command being timed: "fallocate -l 2G fallocate-test"
User time (seconds): 0.00
System time (seconds): 0.00
Percent of CPU this job got: 80%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.00
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 724
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 231
Voluntary context switches: 5
Involuntary context switches: 6
Swaps: 0
File system inputs: 80
File system outputs: 72
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
There we go :)
> Filesystem type is: 9123683e
> File size of fallocate-test is 2147483648 (524288 blocks, blocksize 4096)
> ext logical physical expected length flags
> 0 0 2626450 2048
> 1 2048 3215128 2628498 2040
> 2 4088 3408631 3217168 2032
> 3 6120 3430045 3410663 2024
> 4 8144 3439999 3432069 2016
> 5 10160 3474610 3442015 1004
> 6 11164 3743715 3475614 1002
[…]
> fallocate-test: 4556 extents found
merkaba:/var/tmp> filefrag -v fallocate-test
Filesystem type is: 9123683e
File size of fallocate-test is 2147483648 (524288 blocks, blocksize 4096)
ext logical physical expected length flags
0 0 8501248 524288 eof
fallocate-test: 1 extent found
Yes, thats the same filesystem :)
> But:
>
> merkaba:/var/tmp> /usr/bin/time rm fallocate-test
> 0.00user 0.24system 0:00.38elapsed 63%CPU (0avgtext+0avgdata 784maxresident)k
> 4464inputs+36184outputs (0major+243minor)pagefaults 0swaps
merkaba:/var/tmp> /usr/bin/time rm fallocate-test
0.00user 0.00system 0:00.00elapsed 100%CPU (0avgtext+0avgdata 784maxresident)k
0inputs+24outputs (0major+243minor)pagefaults 0swaps
> Some more information on the filesystem in question:
>
> merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs fi sh
> failed to read /dev/sr0
> Label: 'debian' uuid: […]
> Total devices 1 FS bytes used 13.56GB
> devid 1 size 18.62GB used 18.62GB path /dev/dm-0
>
> Btrfs v0.19-239-g0155e84
>
>
> merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs fi df /
> Disk size: 18.62GB
> Disk allocated: 18.62GB
> Disk unallocated: 0.00
> Used: 13.56GB
> Free (Estimated): 3.31GB (Max: 3.31GB, min: 3.31GB)
> Data to disk ratio: 91 %
>
>
> merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs fi disk-usage /
> Data,Single: Size:15.10GB, Used:12.94GB
> /dev/dm-0 15.10GB
>
> Metadata,Single: Size:8.00MB, Used:0.00
> /dev/dm-0 8.00MB
>
> Metadata,DUP: Size:1.75GB, Used:630.11MB
> /dev/dm-0 3.50GB
>
> System,Single: Size:4.00MB, Used:0.00
> /dev/dm-0 4.00MB
>
> System,DUP: Size:8.00MB, Used:4.00KB
> /dev/dm-0 16.00MB
>
> Unallocated:
> /dev/dm-0 0.00
> merkaba:/home/martin/Linux/Dateisysteme/BTRFS/btrfs-progs-unstable> ./btrfs dev disk-usage /
> /dev/dm-0 18.62GB
> Data,Single: 15.10GB
> Metadata,Single: 8.00MB
> Metadata,DUP: 3.50GB
> System,Single: 4.00MB
> System,DUP: 16.00MB
> Unallocated: 0.00
Thanks,
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7
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2012-12-09 11:12 How to refresh degraded BTRFS? free space fragmentation, file fragmentation Martin Steigerwald
2012-12-09 11:20 ` Martin Steigerwald
2013-01-16 20:39 ` Martin Steigerwald
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