Re: open(O_DIRECT) on a tmpfs?

[Peter Staubach]

Hugh Dickins wrote:
> On Thu, 4 Jan 2007, Bill Davidsen wrote:
>   
> > In many cases the use of O_DIRECT is purely to avoid impact on cache used by
> > other applications. An application which writes a large quantity of data will
> > have less impact on other applications by using O_DIRECT, assuming that the
> > data will not be read from cache due to application pattern or the data being
> > much larger than physical memory.
> >     
>
> I see that as a good argument _not_ to allow O_DIRECT on tmpfs,
> which inevitably impacts cache, even if O_DIRECT were requested.
>
> But I'd also expect any app requesting O_DIRECT in that way, as a caring
> citizen, to fall back to going without O_DIRECT when it's not supported.

I suppose that one could also argue that the backing store for tmpfs
is the memory itself and thus, O_DIRECT could or should be supported.

   Thanx...

      ps
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