Messages in this thread | | | Date | Fri, 4 Jun 2004 12:11:08 +0300 (EEST) | From | Catalin BOIE <> | Subject | Re: why swap at all? |
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Hello!
> But swap behaviour kills performance even when memory is more than adequate. > Consider building a DVD image in a 4GB system. The i/o forces all of the > unused programs out, in spite of the fact that an extra 100MB doesn't make a > measurable difference in performance. But when I click Mozilla paging most of > it in from disk make a big difference in performance to the user.
I think that kernel cannot know that you need some data once or more. This is fadvise for. With my wrapper (http://kernel.umbrella.ro) for fadvise you can do this: NOCA_SIZE=128 NOCA_READ=1 NOCA_WRITE=1 NOCA_RA=1 \ noca mkisofs -R -o /tmp/1.iso /tmp/data
This means: NOCA_SIZE: Call fadvise only after 128KiB was read/wrote. NOCA_RA: call fadvise with POSIX_FADV_SEQUENTIAL NOCA_READ: use fadvise(POSIX_FADV_DONTNEED) for reads (because you don't need anymore the source files) NOCA_WRITE: use fadvise(POSIX_FADV_DONTNEED) for writes (because it's useless to cache the end of the ISO)
Do this program resolve your problem?
> The problems with small memory are different in kind, when not even the > programs will fit in memory at the same time, or will leave next to nothing > for i/o, swap is required for performance. But on a large memory system I > believe the gain to pain ratio is way too low with the current VM. The > solution at the moment is to turn off swap, which as you note has other > problems (can't move between zones without swap?) which in theory could > really hang a system. > > -- > -bill davidsen (davidsen@tmr.com) > "The secret to procrastination is to put things off until the > last possible moment - but no longer" -me > - > 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/ >
--- Catalin(ux aka Dino) BOIE catab at deuroconsult.ro http://kernel.umbrella.ro/ - 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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