2009-01-06 18:49:26

by Eric Hopper

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Subject: nosync, an idea for general filesystem mount flag

Maybe somebody has thought of this before. But I think it would be
useful to have a mount flag telling the filesystem layer that a certain
filesystem never ever needs to be synced, even when the 'sync' system
call is called.

My /tmp, for example, is reformatted on each and every boot. There is
no reason for anything written to /tmp to ever hit the disk. The only
reason is to make room for something else in memory.

I think this could potentially help out notebooks that only had solid
state drives.

Anyway, just a random thought,
--
I am not an LKML member, so please include me in the 'To' or 'Cc' field
if you want me to see your message. -- Eric Hopper (hopper ^at^
omnifarious ^dot^ ^o^ ^r^ ^g^)


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2009-01-07 17:38:24

by Chris Snook

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Subject: Re: nosync, an idea for general filesystem mount flag

Eric Hopper wrote:
> Maybe somebody has thought of this before. But I think it would be
> useful to have a mount flag telling the filesystem layer that a certain
> filesystem never ever needs to be synced, even when the 'sync' system
> call is called.
>
> My /tmp, for example, is reformatted on each and every boot. There is
> no reason for anything written to /tmp to ever hit the disk. The only
> reason is to make room for something else in memory.
>
> I think this could potentially help out notebooks that only had solid
> state drives.
>
> Anyway, just a random thought,

This is why tmpfs was written, but if you're using an SSD with large erase
blocks, and want to avoid setting up a swap partition, you could put the
filesystem on a loop device instead. The sync calls would be absorbed as writes
to the non-sync backing file. It's slightly more complicated to set up, and
slightly less flexible, but the next generation SSDs won't have problems with
random write performance, so the convenience of implementing such an option
would be rather short-lived. It's not a fundamentally evil idea, but it just
doesn't seem to be worth the effort, particularly to maintain it for the rest of
eternity.

-- Chris