Re: [PATCH] O_STREAMING - flag for optimal streaming I/O

[Giuliano Pochini <pochini@shiny.it>]

>> When a process opens a file with O_STREAMING, it tells the kernel
>> it will use the data only once, but it tells nothing about other
>> tasks. If that process reads something which is already cached,
>> then it must not drop it because someone other used it recently
>> and IMHO pagecache only should be allowed to drop it.
>
> You are missing the point.  If the app thinks that might happen, it
> shouldn't use O_STREAMING.
> 
> Though, how do you get around some binary app using O_STREAMING when it
> shouldn't?

Yes, it is with the current behaviour of O_STREAMING. If we change it to
what I said above, O_STREAMING becomes useful in a larger set of cases
with no drawbacks, I think. To not drop pages that were not loaded with
O_STREAMING flag sounds simple, but I don't know how much it is easy to
implement.


Bye.