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Date: Thu, 26 Mar 2009 17:27:43 -0700 (PDT) From: Linus Torvalds <torvalds@...ux-foundation.org> To: Andrew Morton <akpm@...ux-foundation.org> cc: Theodore Tso <tytso@....edu>, David Rees <drees76@...il.com>, Jesper Krogh <jesper@...gh.cc>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: Linux 2.6.29 On Thu, 26 Mar 2009, Andrew Morton wrote: > > userspace can do it quite easily. Run a self-tuning script after > installation and when the disk hardware changes significantly. Uhhuh. "user space can do it". That's the global cop-out. The fact is, user-space isn't doing it, and never has done anything even _remotely_ like it. In fact, I claim that it's impossible to do. If you give me a number for the throughput of your harddisk, I will laugh in your face and call you a moron. Why? Because no such number exists. It depends on the access patterns. If you write one large file, the number will be very different (and not just by a few percent) from the numbers of you writing thousands of small files, or re-writing a large database in random order. So no. User space CAN NOT DO IT, and the fact that you even claim something like that shows a distinct lack of thought. > Maybe we should set the tunables to 99.9% to make it suck enough to > motivate someone. The only times tunables have worked for us is when they auto-tune. IOW, we don't have "use 35% of memory for buffer cache" tunables, we just dynamically auto-tune memory use. And no, we don't expect user space to run some "tuning program for their load" either. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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