Re: [PATCH -mm] make swapin readahead skip over holes

[KOSAKI Motohiro]

(1/9/12 6:10 PM), Rik van Riel wrote:
> Ever since abandoning the virtual scan of processes, for scalability
> reasons, swap space has been a little more fragmented than before.
> This can lead to the situation where a large memory user is killed,
> swap space ends up full of "holes" and swapin readahead is totally
> ineffective.
>
> On my home system, after killing a leaky firefox it took over an
> hour to page just under 2GB of memory back in, slowing the virtual
> machines down to a crawl.
>
> This patch makes swapin readahead simply skip over holes, instead
> of stopping at them.  This allows the system to swap things back in
> at rates of several MB/second, instead of a few hundred kB/second.

If I understand correctly, this patch have

Pros
 - increase IO throughput
Cons
 - increase a risk to pick up unrelated swap entries by swap readahead


The changelog explained former but doesn't explained latter. I'm a bit
hesitate now.
--
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/