Messages in this thread | | | Date | Wed, 19 Oct 2005 13:06:51 +0200 | From | gfiala@s ... | Subject | Re: large files unnecessary trashing filesystem cache? |
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Zitat von Bodo Eggert <7eggert@gmx.de>: > You can alyo cat a big file into /dev/null. I made those examples in order > to demonstrate the problem with using O_DIRECT.
O_DIRECT has to much impact at the mentioned "vdr" due to unwanted side effects either.
> > OTOH, I don't realtime stuff on my computer, so I'm not really affected, > but I'll try to show it anyway. > > > > Changing a few programs will only partly cover the problems. > > > > > > I guess the solution would be using random cache eviction rather than > > > a FIFO. I never took a look the cache mechanism, so I may very well be > > > wrong here. > > > > Read-only pages should be re-cycled really easily & quickly. I can't > > belive read-only pages are causing you all the trouble. > > Just a q&d test: > > $ time ls -l $DIR > /dev/null > real 0m0.442s > user 0m0.008s > sys 0m0.024s > > $ time ls -l $DIR > /dev/null > real 0m0.077s > user 0m0.008s > sys 0m0.008s > > cat $BIGFILES_1.5GB > /Dev/null > > $ time ls -l $DIR > /dev/null > real 0m0.270s > user 0m0.008s > sys 0m0.008s > > $ time ls -l $DIR > /dev/null > real 0m0.078s > user 0m0.004s > sys 0m0.004s > > Thanks for pointing this out - this clearly shows the effect. Now consider a mildly loaded multitasking environment running X, some services, window-manager, email, maybe some databases and a streaming video-application at once (so does mine) - the video-file will have unwanted impact on all the other applications - leading to unnecessary reloads of lots of files, inodes etc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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