Messages in this thread | | | Date | Wed, 11 Jan 2012 16:30:12 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH v2 -mm] make swapin readahead skip over holes |
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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 :)
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