Mailinglist Archive: opensuse (1239 mails)

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[opensuse] Re: XFS and openSUSE 12.1
Roger Oberholtzer wrote:
Any buffers are filled up very quickly when you write 25 MB/Sec. So
something happening after 30 minutes is probably not related to general
buffering.
---
Probably not on your config... 10GB? That'd take about 400s,
but 1800 would take about 45GB of buffering at that rate.

The standard jpeg compression library does indeed do little writes. But
these are via fwrite, so they are buffered via the FILE mechanism. I go
not change the buffer sizes.
----
Looking at the includes on my system, that implies you are doing
pretty small writes -- default buffer size on fwrite is 8192 bytes.

I don't know how to change that, but that is a bit on the
small size.


Do you know if your disc is writing continuously while you execute,
or do you get disk-i/o only ever 30 minutes? ;-)

The disks are accessed every few seconds.
---
Well, there ya go -- if you wanted, you could put those
extra cpu's to work doing encoding and have 1 process that handles writing to
disk.



I do not think the kernel is the culprit. I think it is the hard disk
itself. We will be trying some higher performance discs.
---
Well it wouldn't be the kernel by itself, it would be a combination of
how the app is making calls. What type of HD are you using? single
platter? low rpm? If you are recording images, it sounds like you don't
need it to go much faster, as the images only come in at a certain speed...

If you look in /proc/sys/fs/xfs, you see the xfs tunables.

One of them "speculative_prealloc_lifetime", -- given that you are only writing
at 1GB/400 seconds, that lifetime would timeout on my machine (set for 300 centiseconds
if it is like the other timeouts).. so upping that, or .. ummm...
Have you changed any defaults in there?

Right now mine look like:
s> for i in *;do
echo "$i: $(<$i)"
done
age_buffer_centisecs: 1500
error_level: 3
filestream_centisecs: 3000
inherit_noatime: 1
inherit_nodefrag: 1
inherit_nodump: 1
inherit_nosymlinks: 0
inherit_sync: 1
irix_sgid_inherit: 0
irix_symlink_mode: 0
panic_mask: 0
rotorstep: 1
speculative_prealloc_lifetime: 300
stats_clear: 0
xfsbufd_centisecs: 100
xfssyncd_centisecs: 3000
---
On low power machines, those might be set higher to turn on the disk less
often...? Those are another area you could fiddle with .. er. experiment
with..;-)


Good luck


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