From: Alexander Tsvetkov <alexander.tsvetkov@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: maxpct option for small xfs filesystems
Date: Tue, 27 Jan 2015 19:23:20 +0300 [thread overview]
Message-ID: <54C7BB78.4060203@oracle.com> (raw)
In-Reply-To: <20150126223715.GA7621@dastard>
On 01/27/2015 01:37 AM, Dave Chinner wrote:
> On Mon, Jan 26, 2015 at 07:14:43PM +0300, Alexander Tsvetkov wrote:
>> Hello,
>>
>> I'm trying to understand the expected behaviour of "maxpct" option
>> in case of small xfs filesystem
>> comparing the maximum percentage defined for this option with the
>> percentage of actually allocated
>> inodes in filesystem, but the result of prepared test case doesn't
>> correspond to the expectations:
>>
>> [root@fedora ~]#mkfs.xfs -f -d size=16m -i maxpct=1 /dev/sdb2
> On 3.19-rc5, immediately after mount:
>
> # df -i /mnt/scratch
> Filesystem Inodes IUsed IFree IUse% Mounted on
> /dev/ram1 640 3 637 1% /mnt/scratch
>
> Which indicates that imaxpct=1 is being calculated correctly, before
> we even look at whether it is being enforced correctly or not.
>
> So, what kernel version?
>
> http://xfs.org/index.php/XFS_FAQ#Q:_What_information_should_I_include_when_reporting_a_problem.3F
I use Fedora20 on vbox virtual machine with latest kernel version available
from fedora repos: 3.17.8-200.fc20.x86_64 and xfsprogs-3.2.1-1.fc20.x86_64.
/dev/sdb test storage is of VDI format, fixed size:
[root@fedora ~]# fdisk -l
Disk /dev/sda: 10.3 GiB, 11005845504 bytes, 21495792 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000011de
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 1026047 512000 83 Linux
/dev/sda2 1026048 20469759 9721856 83 Linux
/dev/sda3 20469760 21493759 512000 82 Linux swap / Solaris
Disk /dev/sdb: 8 GiB, 8589934592 bytes, 16777216 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00006ee7
Device Boot Start End Blocks Id System
/dev/sdb1 2048 8390655 4194304 83 Linux
/dev/sdb2 8390656 16777215 4193280 83 Linux
>> [root@fedora ~]# for i in {0..100000}; do str=$(mktemp
>> --tmpdir=/mnt/scratch tmp.XXXXXXXXXX); echo $str; done
> Which is a complex (and very slow!) way of doing:
>
> # for i in {0..100000}; do echo > /mnt/scratch/$i ; done 2> /dev/null
>
>> filesystem is full with created files:
>>
>> [root@fedora ~]# df -Th | grep scratch
>> /dev/sdb2 xfs 13M 13M 148K 99% /mnt/scratch
> # df -Th /mnt/scratch
> Filesystem Type Size Used Avail Use% Mounted on
> /dev/ram1 xfs 13M 1.1M 12M 9% /mnt/scratch
> # df -i /mnt/scratch
> Filesystem Inodes IUsed IFree IUse% Mounted on
> /dev/ram1 640 640 0 100% /mnt/scratch
>
>> and from the number of actually created inodes:
>>
>> [root@fedora ~]# xfs_db -c "blockget -n" -c "ncheck" /dev/sdb2 | wc -l
>> 40512
> That's a directory structure entry count, equivalent to 'find
> /mnt/scratch | wc -l', not an allocated inode count which is what
> 'df -i' reports.
manual page for xfs_db ncheck says about inode numbers not a
directory entry numbers:
"ncheck [-s] [-i ino] Print name-inode pairs"
> Even so, on 3.19-rc5:
>
> # xfs_db -c "blockget -n" -c "ncheck" /dev/ram1 | wc -l
> 637
>
> which matches what 'df -i' tells us about allocated inodes and hence
> imaxpct is working as expected.
I have not the same results, just installed 3.19-rc6 and repeated the test,
df -i reports 640 inodes for filesystem, but actually created 40512 files:
[root@fedora ~]# mkfs.xfs -f -d size=16m -i maxpct=1 /dev/sdb2
meta-data=/dev/sdb2 isize=256 agcount=1, agsize=4096 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0 finobt=0
data = bsize=4096 blocks=4096, imaxpct=1
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal log bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
[root@fedora ~]# mount /dev/sdb2 /mnt/scratch/
fill with files until enospc...
[root@fedora ~]# df -i /mnt/scratch/
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/sdb2 640 640 0 100% /mnt/scratch
[root@fedora ~]# df -Th /mnt/scratch/
Filesystem Type Size Used Avail Use% Mounted on
/dev/sdb2 xfs 13M 13M 156K 99% /mnt/scratch
[root@fedora ~]# umount /mnt/scratch
[root@fedora ~]# xfs_db -c "blockget -n" -c "ncheck" /dev/sdb2 | wc -l
40512
Looking into ncheck output there are 40512 pairs reported in the output
each with own unique
inode number. ncheck doesn't report inodes count by definition, but what
does these
40512 reported inode numbers mean if only actually 640 inodes were
allocated? From another hand
each new file should have associated meta-data in the corresponding
allocated inode structure, so for
40512 newly created files I expect the same count of allocated inodes,
is it correct?
> Cheers,
>
> Dave.
Thanks,
Alexander Tsvetkov
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next prev parent reply other threads:[~2015-01-27 16:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-26 16:14 maxpct option for small xfs filesystems Alexander Tsvetkov
2015-01-26 22:37 ` Dave Chinner
2015-01-27 16:23 ` Alexander Tsvetkov [this message]
2015-01-27 16:31 ` Eric Sandeen
2015-01-27 19:15 ` Eric Sandeen
2015-01-28 10:41 ` Alexander Tsvetkov
2015-01-28 15:44 ` Eric Sandeen
2015-01-28 18:05 ` Eric Sandeen
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