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Temporary files: RAM or disk?

Temporary files: RAM or disk?

Posted Jun 4, 2012 10:33 UTC (Mon) by andresfreund (subscriber, #69562)
In reply to: Temporary files: RAM or disk? by dvdeug
Parent article: Temporary files: RAM or disk?

Mount your filesystems with O_SYNC and see how long you can endure that. Making everything synchronous by default is a completely useless behaviour. *NO* general purpose OS in the last years does that.
Normally you need only very few points where you fsync (or equivalent) and quite some more places where you write data...


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Temporary files: RAM or disk?

Posted Jun 4, 2012 11:20 UTC (Mon) by neilbrown (subscriber, #359) [Link]

To be fair, O_SYNC is much stronger than what some people might reasonably want to expect.

O_SYNC means every write request is safe before the write system call returns.

An alternate semantic is that a file is safe once the last "close" on it returns. I believe this has been implemented for VFAT filesystems which people sometimes like to pull out of their computers without due care.
It is quite an acceptable trade-off in that context.

This is nearly equivalent to always calling fsync() just before close().

Adding a generic mount option to impose this semantic on any fs might be acceptable. It might at least silence some complaints.

Temporary files: RAM or disk?

Posted Jun 4, 2012 12:19 UTC (Mon) by andresfreund (subscriber, #69562) [Link]

> To be fair, O_SYNC is much stronger than what some people might reasonably want to expect.
> O_SYNC means every write request is safe before the write system call returns.
Hm. Not sure if that really is what people expect. But I can certainly see why it would be useful for some applications. Should probably be a fd option or such though? I would be really unhappy if a rm -rf or copy -r would behave that way.

Sometimes I wish userspace controllable metadata transactions where possible with a sensible effort/interface...


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