On 05/14/2012 08:58 PM, ehrhardt@xxxxxxxxxxxxxxxxxx wrote: > 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. I think we have already done it. Look at shrink_mem_cgroup_zone which ends up calling shrink_page_list so we already have applied I/O plugging. > 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. We could enhance write out by batch like ext4_bio_write_page. > > 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> > -- Kind regards, Minchan Kim -- 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>