Messages in this thread | | | Date | Wed, 19 Jul 2006 10:18:44 +0100 | From | Ian Stirling <> | Subject | Re: Improvement on memory subsystem |
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Valdis.Kletnieks@vt.edu wrote: > On Tue, 18 Jul 2006 18:03:54 +0800, yunfeng zhang said: > > >>2. Read-ahead process during page-in/out (page fault or swap out) should be >>based on its VMA to enhance IO efficiency instead of the relative physical pages >>in swap space. > > > But wouldn't that end up causing a seek storm, rather than handling the pages > in the order that minimizes the total seek distance, no matter where they are > in memory? Remember - if you have a 2Ghz processor, and a disk that seeks in 1 > millisecond, every seek is (*very* roughly) about 2 million instructions. So > if we can burn 20 thousand instructions finding a read order that eliminates > *one* seek, we're 1.98M instructions ahead.
To paraphrase shakespear - all the world is not a P4 - and all the swap devices are not hard disks.
For example - I've got a 486/33 laptop with 12M RAM that I sometimes use , with swapping to a 128M PCMCIA RAM card that I got from somewhere.
20K instructions wasted on a device with no seek time is just annoying.
And on my main laptop - I have experimented with swap-over-wifi to a large ramdisk on my server - which works quite well. (until the wifi connection falls over). - 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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