Dear Linux folks,
Short problem statement: Sometimes changing into a directory on a file
server wit 30 TB hardware RAID and 100 TB software RAID both formatted
with XFS takes several seconds.
On a Dell PowerEdge T630 with two Xeon CPU E5-2603 v4 @ 1.70GHz and 96
GB RAM a 30 TB hardware RAID is served by the hardware RAID controller
and a 100 TB MDRAID software RAID connected to a Microchip 1100-8e both
formatted using XFS. Currently, Linux 5.4.39 runs on it.
```
$ more /proc/version
Linux version 5.4.39.mx64.334 (root@xxxxxxxxxxxxxxxxx) (gcc version
7.5.0 (GCC)) #1 SMP Thu May 7 14:27:50 CEST 2020
$ dmesg | grep megar
[ 10.322823] megaraid cmm: 2.20.2.7 (Release Date: Sun Jul 16 00:01:03
EST 2006)
[ 10.331910] megaraid: 2.20.5.1 (Release Date: Thu Nov 16 15:32:35 EST
2006)
[ 10.345055] megaraid_sas 0000:03:00.0: BAR:0x1 BAR's
base_addr(phys):0x0000000092100000 mapped virt_addr:0x0000000059ea5995
[ 10.345057] megaraid_sas 0000:03:00.0: FW now in Ready state
[ 10.351868] megaraid_sas 0000:03:00.0: 63 bit DMA mask and 32 bit
consistent mask
[ 10.361655] megaraid_sas 0000:03:00.0: firmware supports msix : (96)
[ 10.369433] megaraid_sas 0000:03:00.0: requested/available msix 13/13
[ 10.377113] megaraid_sas 0000:03:00.0: current msix/online cpus : (13/12)
[ 10.385190] megaraid_sas 0000:03:00.0: RDPQ mode : (disabled)
[ 10.392092] megaraid_sas 0000:03:00.0: Current firmware supports
maximum commands: 928 LDIO threshold: 0
[ 10.403895] megaraid_sas 0000:03:00.0: Configured max firmware
commands: 927
[ 10.416840] megaraid_sas 0000:03:00.0: Performance mode :Latency
[ 10.424029] megaraid_sas 0000:03:00.0: FW supports sync cache : No
[ 10.431417] megaraid_sas 0000:03:00.0: megasas_disable_intr_fusion is
called outbound_intr_mask:0x40000009
[ 10.486158] megaraid_sas 0000:03:00.0: FW provided supportMaxExtLDs:
1 max_lds: 64
[ 10.495502] megaraid_sas 0000:03:00.0: controller type : MR(2048MB)
[ 10.502988] megaraid_sas 0000:03:00.0: Online Controller Reset(OCR) :
Enabled
[ 10.511445] megaraid_sas 0000:03:00.0: Secure JBOD support : No
[ 10.518543] megaraid_sas 0000:03:00.0: NVMe passthru support : No
[ 10.525834] megaraid_sas 0000:03:00.0: FW provided TM TaskAbort/Reset
timeout: 0 secs/0 secs
[ 10.536251] megaraid_sas 0000:03:00.0: JBOD sequence map support : No
[ 10.543931] megaraid_sas 0000:03:00.0: PCI Lane Margining support : No
[ 10.574406] megaraid_sas 0000:03:00.0: megasas_enable_intr_fusion is
called outbound_intr_mask:0x40000000
[ 10.585995] megaraid_sas 0000:03:00.0: INIT adapter done
[ 10.592409] megaraid_sas 0000:03:00.0: JBOD sequence map is disabled
megasas_setup_jbod_map 5660
[ 10.603273] megaraid_sas 0000:03:00.0: pci id :
(0x1000)/(0x005d)/(0x1028)/(0x1f42)
[ 10.612815] megaraid_sas 0000:03:00.0: unevenspan support : yes
[ 10.619919] megaraid_sas 0000:03:00.0: firmware crash dump : no
[ 10.627013] megaraid_sas 0000:03:00.0: JBOD sequence map : disabled
$ dmesg | grep 1100-8e
[ 25.853170] smartpqi 0000:84:00.0: added 11:2:0:0 0000000000000000
RAID Adaptec 1100-8e
[ 25.867069] scsi 11:2:0:0: RAID Adaptec 1100-8e
2.93 PQ: 0 ANSI: 5
$ xfs_info /dev/sdc
meta-data=/dev/sdc isize=512 agcount=28,
agsize=268435455 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=0, rmapbt=0
= reflink=0
data = bsize=4096 blocks=7323648000, imaxpct=5
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=521728, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
$ xfs_info /dev/md0
meta-data=/dev/md0 isize=512 agcount=102,
agsize=268435328 blks
= sectsz=4096 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=0, rmapbt=0
= reflink=0
data = bsize=4096 blocks=27348633088, imaxpct=1
= sunit=128 swidth=1792 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=521728, version=2
= sectsz=4096 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
$ df -i /dev/sdc
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/sdc 2929459200 4985849 2924473351 1% /home/pmenzel
$ df -i /dev/md0
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/md0 2187890624 5331603 2182559021 1% /jbod/M8015
```
After not using a directory for a while (over 24 hours), changing into
it (locally) takes over five seconds or doing some git operations. For
example the Linux kernel source git tree located in my home directory.
(My shell has some git integration showing the branch name in the prompt
(`/usr/share/git-contrib/completion/git-prompt.sh`.) Once in that
directory, everything reacts instantly again. When waiting the Linux
pressure stall information (PSI) shows IO resource contention.
Before:
$ grep -R . /proc/pressure/
/proc/pressure/io:some avg10=0.40 avg60=0.10 avg300=0.10
total=48330841502
/proc/pressure/io:full avg10=0.40 avg60=0.10 avg300=0.10
total=48067233340
/proc/pressure/cpu:some avg10=0.00 avg60=0.00 avg300=0.00
total=755842910
/proc/pressure/memory:some avg10=0.00 avg60=0.00 avg300=0.00
total=2530206336
/proc/pressure/memory:full avg10=0.00 avg60=0.00 avg300=0.00
total=2318140732
During `git log stable/linux-5.10.y`:
$ grep -R . /proc/pressure/
/proc/pressure/io:some avg10=26.20 avg60=9.72 avg300=2.37
total=48337351849
/proc/pressure/io:full avg10=26.20 avg60=9.72 avg300=2.37
total=48073742033
/proc/pressure/cpu:some avg10=0.00 avg60=0.00 avg300=0.00
total=755843898
/proc/pressure/memory:some avg10=0.00 avg60=0.00 avg300=0.00
total=2530209046
/proc/pressure/memory:full avg10=0.00 avg60=0.00 avg300=0.00
total=2318143440
The current explanation is, that over night several maintenance scripts
like backup/mirroring and accounting scripts are run, which touch all
files on the devices. Additionally sometimes other users run cluster
jobs with millions of files on the software RAID. Such things invalidate
the inode cache, and “my” are thrown out. When I use it afterward it’s
slow in the beginning. There is still free memory during these times
according to `top`.
Does that sound reasonable with ten million inodes? Is that easily
verifiable?
Kind regards,
Paul
