Re: dd interface to posix_fadvise

[Paul Eggert]

Pádraig Brady <address@hidden> writes:

>> If it's purely a performance improvement, I'd be inclined to
>> enable it all the time.  That's even simpler, from the user's
>> point of view. 
>
> Well it's specific to the future data usage whether it's
> better to cache or not, and dd can't know this.

But posix_fadvise is supposed to tell the OS how the current
application (in this case, 'dd') will behave.  It is not supposed to
tell the OS how other applications will behave.

Since the advice is only about what 'dd' will do, and 'dd' is always
sequential, POSIX_FADV_SEQUENTIAL seems entirely appropriate; I don't
see why it'd be wrong, except if the OS has a performance bug of some
sort.