From: Ehrhardt Christian <ehrhardt@xxxxxxxxxxxxxxxxxx> From: Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx> In an memory overcommitment scneario with KVM I ran into a lot of wiats for swap. While checking the I/O done on the swap disks I found almost all I/Os to be done as single page 4k request. Despite the fact that swap in is a batch of 1<<page-cluster pages as swap readahead and swap out is a list of pages written in shrink_page_list. [1/2 swap in improvment] The read patch shows improvements of up to 50% swap throughput, much happier guest systems and even when running with comparable throughput a lot I/O per seconds saved leaving resources in the SAN for other consumers. [2/2 documentation] While doing so I also realized that the documentation for proc/sys/vm/page-cluster is no more matching the code [missing patch #3] I tried to get a similar patch working for swap out in shrink_page_list. And it worked in functional terms, but the additional mergin was negligible. Maybe the cond_resched triggers much mor often than I expected, I'm open for suggestions regarding improving the pagout I/O sizes as well. Kind regards, Christian Ehrhardt Christian Ehrhardt (2): swap: allow swap readahead to be merged documentation: update how page-cluster affects swap I/O Documentation/sysctl/vm.txt | 12 ++++++++++-- mm/swap_state.c | 5 +++++ 2 files changed, 15 insertions(+), 2 deletions(-) -- 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>