On Wed, Jul 20, 2011 at 11:53 AM, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > per-task block plug can reduce block queue lock contention and increase request > merge. Currently page reclaim doesn't support it. I originally thought page > reclaim doesn't need it, because kswapd thread count is limited and file cache > write is done at flusher mostly. > When I test a workload with heavy swap in a 4-node machine, each CPU is doing > direct page reclaim and swap. This causes block queue lock contention. In my > test, without below patch, the CPU utilization is about 2% ~ 7%. With the > patch, the CPU utilization is about 1% ~ 3%. Disk throughput isn't changed. Why doesn't it enhance through? It means merge is rare? > This should improve normal kswapd write and file cache write too (increase > request merge for example), but might not be so obvious as I explain above. CPU utilization enhance on 4-node machine with heavy swap? I think it isn't common situation. And I don't want to add new stack usage if it doesn't have a benefit. As you know, direct reclaim path has a stack overflow. These days, Mel, Dave and Christoph try to remove write path in reclaim for solving stack usage and enhance write performance. -- 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>