Big speed decrease: 3.7 -> 3.8 or later

[DirkS]

Hi all,

Some time ago I observed that Knoppix 3.7 was noticably faster than 3.8 and later when doing a copy over a network connection (1.5 to 4 times faster).

A few days ago I observed the following timings when copying all files from a DVD (about 3.9GB) to a HD:

Knoppix 3.7: a little more than 7 minutes
Windows XP: a little more than 7 minutes
Knoppix 4.02: a little more than 45 minutes (!!!!)

I was flabbergasted! Fourtyfive minutes, about 6 times the time of Knoppix 3.7 and Windows XP - that's inexcusable!

While searching the forum I didn't see any similar observation, but I came across a hint about the major change between 3.7 and anything later: UnionFS.
So, unionfs is the major suspect.

My questions:
- is this perhaps a known issue?
- Has anybody else observed any speed penalties between 3.7 and anything later?
- is another part of knoppix at fault instead of unionfs, maybe?
- if the culprit is indeed unionfs:
-- Is there way to speed things up when using it?
-- if not or if the possible speedup is too small: Is there a way to get rid of unionfs in knoppix > 3.7? Maybe not completely but for special cases, like, when a CD/DVD is involved?

All answers are greatly appreciated!

Aside of the above, Knoppix has become my favorite distro, I even replaced a SuSE 10.0 with a knoppix installation - so BIG THANKS for the great work!
Then again, unless I find a solution for this speed problem, I cannot recommend it to friends anymore, at least nothing above 3.7. Please help!

Dirk

[Harry Kuhman]

Knoppix 3.7 by default turned DMA on. 4.0.2 by default does not. You might want to try this experiment again by using the cheat code to enable DMA.

[DirkS]

Ah. Maybe. I will try again later today. Hmm, do you happen to know when this default setting has been changed?

Thanks a heap!!
Dirk

[Harry Kuhman]

Don't know the exact point of change, but I know it was enabled in 3.7 and is disabled now. Caused too many booting problems for too many people. dma=off seems to be a better default, as it will let many (but not all) people who can use DMA still boot, although things will be slower. Forget which way 3.8 was.

[DirkS]

Thanks! I'll see and report the results later (hopefully less than 24 hours later).

But still... 6 times slower when reading from a new DVD drive... well, I can hardly wait to get home now.

[DirkS]

Result for 4.02 with dma:
3.2GB in 6m41. Phew! It is the dma. Now I'm releaved.

Harry, thank you VERRY much!!

I didn't expect the dma to make such a big difference. 6 times! Whew!