performance issues running Fedora from an USB pen

artu72 · #1 25th March 2009, 03:25 PM

Hi to all,

I have succesfully installed lates fedora 10 /x86_64 respin on a computer on a USB pen, since I cannot modify the internal hard disk partition table. I have however noticed that, both in installation and in usage, the system, when accessing to usb drive where the root partition is located, freezes at regular time intervals, waits for about twenty seconds and then resumes. How can I prevent this performance issue due to some usb bus timeout ? In the system logs there is nothing related to usb problems, and the usb pen works properly as storage device.

The usb pen is a 16 GB sandisk cruzer (of course I have removed the U3 feature).

Thank you.

notageek · #2 26th March 2009, 04:32 PM

You can expect some performance issue, I don't think is as fast as a hard drive. Can you please post "df -hT" of the live system.

I'm interested in knowing the root device, is it /dev/sdX or /dev/ubX? Also can you run "hdparm -tT /dev/XXX" and report back.

artu72 · #3 27th March 2009, 02:59 PM

Quote:

Originally Posted by notageek

You can expect some performance issue, I don't think is as fast as a hard drive. Can you please post "df -hT" of the live system.

I'm interested in knowing the root device, is it /dev/sdX or /dev/ubX? Also can you run "hdparm -tT /dev/XXX" and report back.

df-hT output:

/dev/sdb1 ext3 14G 3.0G 11G 23% /
tmpfs tmpfs 1001M 604K 1001M 1% /dev/shm
/dev/sr0 iso9660 4.1G 4.1G 0 100% /media/"FU 20090210 10 x86_64 DVD"

As you can see, the root partition is mounted over /dev/sdb1.

Here is hdparm -tT /dev/sdb1 output:

Timing cached reads: 2236 MB in 2.00 seconds = 1118.09 MB/sec
Timing buffered disk reads: 74 MB in 3.08 seconds = 24.04 MB/sec

that you compare with the hard disk performance:

hdparm -tT /dev/sda2

/dev/sda2:
Timing cached reads: 2090 MB in 2.00 seconds = 1044.92 MB/sec
Timing buffered disk reads: 226 MB in 3.03 seconds = 74.69 MB/sec

I am aware that an USB pen will not present same performances as an hard disk, but my problem is due to the frequent freezing of the system (hint: when this happens, the pdflush process is in D state).

Perhaps should I tune my ext3 filesystem with noatime option ?

notageek · #4 27th March 2009, 04:40 PM

I see that your reads are faster than your writes and infact read from the pendrive is faster than the hard-drive, hdparm report is independent of the filesystem, however you may try using noatime on ext3 and see if it improves your system performance.

You could also play with these values and see if it improves your performance. (Lower the better)

Code:

/proc/sys/vm/dirty_background_ratio
/proc/sys/vm/dirty_ratio
/proc/sys/vm/dirty_expire_centisecs

Also can you post "cat /proc/meminfo" before you try. Also post the values of the above.

Standard Disclaimer: I or Fedora Forum cannot be responsible for any of the commands borking your system and/or pendrive

artu72 · #5 27th March 2009, 04:49 PM

Quote:

Originally Posted by notageek

I see that your reads are faster than your writes and infact read from the pendrive is faster than the hard-drive, hdparm report is independent of the filesystem, however you may try using noatime on ext3 and see if it improves your system performance.

You could also play with these values and see if it improves your performance. (Lower the better)

Code:

/proc/sys/vm/dirty_background_ratio
/proc/sys/vm/dirty_ratio
/proc/sys/vm/dirty_expire_centisecs

Also can you post "cat /proc/meminfo" before you try. Also post the values of the above.

Standard Disclaimer: I or Fedora Forum cannot be responsible for any of the commands borking your system and/or pendrive

I am fully aware regarding your last disclaimer !

The requested values follow (note that often the usb_storage processes goes in delayed state when the system freezes)

[root@ntmastellone yum.repos.d]# cat /proc/sys/vm/dirty_background_ratio
5
[root@ntmastellone yum.repos.d]# cat /proc/sys/vm/dirty_ratio
10
[root@ntmastellone yum.repos.d]# cat /proc/sys/vm/dirty_expire_centisecs
2999
[root@ntmastellone yum.repos.d]# cat /proc/meminfo
MemTotal: 2049948 kB
MemFree: 735792 kB
Buffers: 30228 kB
Cached: 514332 kB
SwapCached: 0 kB
Active: 741328 kB
Inactive: 375940 kB
SwapTotal: 1052248 kB
SwapFree: 1052248 kB
Dirty: 204 kB
Writeback: 0 kB
AnonPages: 572824 kB
Mapped: 91572 kB
Slab: 49384 kB
SReclaimable: 32972 kB
SUnreclaim: 16412 kB
PageTables: 21068 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 2077220 kB
Committed_AS: 1228988 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 536932 kB
VmallocChunk: 34359199227 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 47100 kB
DirectMap2M: 2039808 kB

notageek · #6 27th March 2009, 04:52 PM

Try this:

Code:

# echo 5 > /proc/sys/vm/dirty_ratio

Quote:

Originally Posted by artu72

note that often the usb_storage processes goes in delayed state when the system freezes

Its because your writes are slow.

artu72 · #7 27th March 2009, 04:59 PM

Quote:

Originally Posted by notageek

Try this:

Code:

# echo 5 > /proc/sys/vm/dirty_ratio

Its because your writes are slow.

Great, that was the right trick !

Should now I tune my ext3 / parameters now, as you suggested ? noatime...

I will insert the echo in rc.local in order to do it at every boot...

notageek · #8 27th March 2009, 05:24 PM

You could give noatime a try, since your hardware is slow in writing, every possible way to limit IO will definitely benefit.

artu72 · #9 27th March 2009, 05:27 PM

Quote:

Originally Posted by notageek

You could give noatime a try, since your hardware is slow in writing, every possible way to limit IO will definitely benefit.

Ok if I change from defaults to defaults,noatime ?

notageek · #10 27th March 2009, 05:38 PM

try "data=writeback" also and TBH if you don't need ext3 you can mount it as ext2, will give you faster performance. An existing ext3 filesystem can be used as ext2.

And yes defaults,noatime too.