On Tuesday 19 February 2008 16:44, KOSAKI Motohiro wrote: > background > ======================================== > current VM implementation doesn't has limit of # of parallel reclaim. > when heavy workload, it bring to 2 bad things > - heavy lock contention > - unnecessary swap out > > abount 2 month ago, KAMEZA Hiroyuki proposed the patch of page > reclaim throttle and explain it improve reclaim time. > http://marc.info/?l=linux-mm&m=119667465917215&w=2 > > but unfortunately it works only memcgroup reclaim. > Today, I implement it again for support global reclaim and mesure it. > > > test machine, method and result > ================================================== > <test machine> > CPU: IA64 x8 > MEM: 8GB > SWAP: 2GB > > <test method> > got hackbench from > http://people.redhat.com/mingo/cfs-scheduler/tools/hackbench.c > > $ /usr/bin/time hackbench 120 process 1000 > > this parameter mean consume all physical memory and > 1GB swap space on my test environment. > > <test result (average of 3 times measurement)> > > before: > hackbench result: 282.30 > /usr/bin/time result > user: 14.16 > sys: 1248.47 > elapse: 432.93 > major fault: 29026 > max parallel reclaim tasks: 1298 > max consumption time of > try_to_free_pages(): 70394 > > after: > hackbench result: 30.36 > /usr/bin/time result > user: 14.26 > sys: 294.44 > elapse: 118.01 > major fault: 3064 > max parallel reclaim tasks: 4 > max consumption time of > try_to_free_pages(): 12234 > > > conclusion > ========================================= > this patch improve 3 things. > 1. reduce unnecessary swap > (see above major fault. about 90% reduced) > 2. improve throughput performance > (see above hackbench result. about 90% reduced) > 3. improve interactive performance. > (see above max consumption of try_to_free_pages. > about 80% reduced) > 4. reduce lock contention. > (see above sys time. about 80% reduced) > > > Now, we got about 1000% performance improvement of hackbench :) > > > > foture works > ========================================================== > - more discussion with memory controller guys.
Hi, Yeah this is definitely needed and a nice result. I'm worried about a) placing a global limit on parallelism, and b) placing a limit on parallelism at all. I think it should maybe be a per-zone thing... What happens if you make it a per-zone mutex, and allow just a single process to reclaim pages from a given zone at a time? I guess that is going to slow down throughput a little bit in some cases though... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
