On 01/11/2012 04:42 PM, Johannes Weiner wrote:
On Wed, Jan 11, 2012 at 04:30:12PM -0500, Rik van Riel wrote:
On 01/11/2012 04:10 PM, Johannes Weiner wrote:
On Wed, Jan 11, 2012 at 02:30:44PM -0500, 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.
The checks done in valid_swaphandles are already done in
read_swap_cache_async as well, allowing us to remove a fair amount
of code.
__swap_duplicate() also checks for whether the offset is within the
swap device range. Do you think we could remove get_swap_cluster()
altogether and just try reading the aligned page_cluster range?
That is how I implemented it originally, but we need
to take the swap_lock so it is cleaner to implement
a helper function in swapfile.c :)
AFAICS, it's only needed to validate the offset against si->max, but
this too is done in __swap_duplicate().
What's otherwise left is just rounding down swp_offset(entry) and
adding 1<< page_cluster to it, that shouldn't need the swap_lock?
Am I missing something?
Good point. I guess we could get rid of get_swap_cluster
afterall and let __swap_duplicate deal with everything.
Andrew, Mel, is that ok with you?
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