Linus very much opposed O_DIRECT from the start. If I remember correctly he only introduced it at the pressure from the "database people" i.e. his beloved Oracle.

No wonder O_DIRECT never saw much love.

"I hope some day we can just rip the damn disaster out."

-- Linus Torvalds, 2007

https://lkml.org/lkml/2007/1/10/235

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jandrewrogers 15 hours ago | parent [-]

This is one of several examples where Linus thinks something is bad because he doesn't understand how it is used.

Something like O_DIRECT is critical for high-performance storage in software for well-understood reasons. It enables entire categories of optimization by breaking a kernel abstraction that is intrinsically unfit for purpose; there is no way to fix it in the kernel, the existence of the abstraction is the problem as a matter of theory.

As a database performance enjoyer, I've been using O_DIRECT for 15+ years. Something like it will always exist because removing it would make some high-performance, high-scale software strictly worse.

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jeffbee 14 hours ago | parent [-]

His lack of industry experience is the root cause of many issues in Linux.

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vacuity 14 hours ago | parent [-]

Although this is somewhat true, I think the bigger issue is expecting Linux to support all these use cases. Even if Linus accepted all use cases, it's a different story to maintain a kernel/OS that supports them all. The story from an engineering standpoint is just too unwieldy. A general-purpose OS can only go so far to optimize countless special-purpose uses.

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tremon 13 hours ago | parent | next [-]

This is not some minor niche use case though, and all other operating systems seem to have no trouble supporting OS fscache bypass.

	▲	vacuity 12 hours ago \| parent [-]
		Considering how big Linux is and how many different use cases it supports, this could well be an undue maintenance burden for Linux where it wouldn't be for other operating systems. Though, I'll grant that I don't know the details here, and of course Linus is...opinionated.

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jeffbee 8 hours ago | parent | prev [-]

I agree. I wish we had more varied operating systems.