Messages in this thread | | | Date | Tue, 16 Apr 2002 12:39:22 -0300 (BRT) | From | Rik van Riel <> | Subject | Re: IO performance problems in 2.4.19-pre5 when writing to DVD-RAM/ZIP/MO |
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On Tue, 16 Apr 2002, Andrea Arcangeli wrote: > On Fri, Apr 05, 2002 at 11:04:18PM +0200, Moritz Franosch wrote:
> > The problem is that writing to a DVD-RAM, ZIP or MO device almost > > totally blocks reading from a _different_ device. Here is some data. > > > > nr bench read write 2.4.18 2.4.19-rc5 expected factor > > 1 dd 30GB HDD DVD-RAM 278 490 60 8.2 > > 2 dd 120GB HDD DVD-RAM 197 438 32 14 > > 3 dd 30GB HDD ZIP 158 239 60 4.0 > > 4 dd 120GB HDD ZIP 142 249 32 7.8 > > 5 dd 30GB HDD 120GB HDD 87 89 60 1.5 > > 6 dd 120GB HDD 30GB HDD 66 69 32 2.2 > > 7 cp 30GB HDD 120GB HDD 97 77 60 1.3 > > 8 cp 120GB HDD 30GB HDD 78 65 50 1.3 > > > > The columns 2.4.18 and 2.4.19-rc5 list execution times in seconds of > > the respective benchmark. The column "expected" lists the time I would > > have expected for the respective benchmark to complete with a > > "perfect" kernel. The "factor" is the factor 2.4.19-rc5 is slower than > > a perfect kernel would be.
> The reason hd is faster is because new algorithm is much better than the > previous mainline code. Now the reason the DVDRAM hangs the machine > more, that's probably because more ram can be marked dirty with those > new changes (beneficial for some workload, but it stalls much more the > fast hd, if there's one very slow blkdev in the system). You can try > decrasing the percent of vm dirty in the system with: > > echo 2 500 0 0 500 3000 3 1 0 >/proc/sys/vm/bdflush
Judging from the performance regression above it would seem the new defaults suck rocks.
Can we please stop optimising Linux for a single workload benchmark and start tuning it for the common case of running multiple kinds of applications and making sure one application can't mess up the others ?
Personally I couldn't care less if my tar went 30% faster if it meant having my desktop unresponsive for the whole time.
regards,
Rik -- http://www.linuxsymposium.org/2002/ "You're one of those condescending OLS attendants" "Here's a nickle kid. Go buy yourself a real t-shirt"
http://www.surriel.com/ http://distro.conectiva.com/
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