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? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>