Re: [RFC][PATCH] swap: send callback when swap slot is freed

[Nitin Gupta]

On 08/12/2009 06:26 PM, Ingo Molnar wrote:
> * Nitin Gupta<ngupta@xxxxxxxxxx>  wrote:
>
> > (Re-sending since I didn't get any reply last time)
> >
> > Currently, we have "swap discard" mechanism which sends a discard
> > bio request when we find a free cluster during scan_swap_map().
> > This callback can come a long time after swap slots are actually
> > freed.
> >
> > This delay in callback is a great problem when (compressed) RAM
> > [1] is used as a swap device. So, this change adds a callback
> > which is called as soon as a swap slot becomes free. For above
> > mentioned case of swapping over compressed RAM device, this is
> > very useful since we can immediately free memory allocated for
> > this swap page.
> >
> > This callback does not replace swap discard support. It is called
> > with swap_lock held, so it is meant to trigger action that
> > finishes quickly. However, swap discard is an I/O request and can
> > be used for taking longer actions.

<snip>

> Shouldnt this be all be unconditional? Sounds like a reasonable VM
> callback. The patch would become a lot smaller as well.


I also think this can be made unconditional as it makes the patch
much cleaner. I made it conditional just to be on path of least
resistance :)

Thanks for looking into this. I will resend the patch removing
all the #ifdef'ery.

Nitin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/