On Mon, 25 Oct 2010, caiqian@xxxxxxxxxx wrote: > Hi everyone, while developing some tests for KSM in LTP Thank you! > - http://marc.info/?l=ltp-list&m=128754077917739&w=2 , noticed that pages_shared, pages_sharing and pages_unshared have different values than the expected values in the tests after read the doc. I am not sure if I misunderstood those values or there were bugs somewhere. You were expecting KSM to share pages between processes, but you were not expecting it to share pages within a process, which it does also. To check the exact numbers, it would be easier if you use page-aligned mmap() rather than byte-aligned malloc() for your MADV_MERGEABLE buffers: some numbers are a little "off" because of part-pages at start and end. > > There are 3 programs (A, B ,C) to allocate 128M memory each using KSM. > > A has memory content equal 'c'. > B has memory content equal 'a'. > C has memory content equal 'a'. > > Then (using the latest mmotm tree), > pages_shared = 2 > pages_sharing = 98292 > pages_unshared = 0 So, after KSM has done its best, it all reduces to 1 page full of 'a's and another 1 page full of 'c's. > > Later, > A has memory content = 'c' > B has memory content = 'b' > C has memory content = 'a'. > > Then, > pages_shared = 4 > pages_sharing = 98282 > pages_unshared = 0 pages_shared 3 would be the obvious: I expect the extra 1 is an artifact of part-pages at start and end of your buffers, a page shared there too. > > Finally, > A has memory content = 'd' > B has memory content = 'd' > C has memory content = 'd' > > Then, > pages_shared = 0 > pages_sharing = 0 > pages_unshared = 0 The children appear to exit(1) as soon as they have filled their buffers with 'd's, so there's nothing left to share. Hugh > > The following was the failed LTP output, > > # ./ksm01 > ksm01 0 TINFO : KSM merging... > ksm01 0 TINFO : child 0 allocates 128 MB filled with 'c'. > ksm01 0 TINFO : child 1 allocates 128 MB filled with 'a'. > ksm01 0 TINFO : child 2 allocates 128 MB filled with 'a'. > ksm01 0 TINFO : check! > ksm01 0 TINFO : run is 1. > ksm01 0 TINFO : pages_shared is 2. > ksm01 1 TFAIL : pages_shared is not 32768. > ksm01 0 TINFO : pages_sharing is 98292. > ksm01 2 TFAIL : pages_sharing is not 32768. > ksm01 0 TINFO : pages_unshared is 0. > ksm01 3 TFAIL : pages_unshared is not 32768. > ksm01 0 TINFO : child 1 continues... > ksm01 0 TINFO : child 1 changes memory content to 'b'. > ksm01 0 TINFO : check! > ksm01 0 TINFO : run is 1. > ksm01 0 TINFO : pages_shared is 4. > ksm01 4 TFAIL : pages_shared is not 0. > ksm01 0 TINFO : pages_sharing is 98282. > ksm01 5 TFAIL : pages_sharing is not 0. > ksm01 0 TINFO : pages_unshared is 0. > ksm01 6 TFAIL : pages_unshared is not 98304. > ksm01 0 TINFO : child 0 continues... > ksm01 0 TINFO : child 0 changes memory content to 'd'. > ksm01 0 TINFO : child 1 continues... > ksm01 0 TINFO : child 1 changes memory content to 'd' > ksm01 0 TINFO : child 2 continues... > ksm01 0 TINFO : child 2 changes memory content to 'd' > ksm01 0 TINFO : check! > ksm01 0 TINFO : run is 1. > ksm01 0 TINFO : pages_shared is 0. > ksm01 7 TFAIL : pages_shared is not 32768. > ksm01 0 TINFO : pages_sharing is 0. > ksm01 8 TFAIL : pages_sharing is not 65536. > ksm01 0 TINFO : pages_unshared is 0. > ksm01 0 TINFO : KSM unmerging... > ksm01 0 TINFO : check! > ksm01 0 TINFO : run is 2. > ksm01 0 TINFO : pages_shared is 0. > ksm01 0 TINFO : pages_sharing is 0. > ksm01 0 TINFO : pages_unshared is 0. > ksm01 0 TINFO : stop KSM. > ksm01 0 TINFO : check! > ksm01 0 TINFO : run is 0. > ksm01 0 TINFO : pages_shared is 0. > ksm01 0 TINFO : pages_sharing is 0. > ksm01 0 TINFO : pages_unshared is 0. > ksm01 9 TFAIL : ksmtest() failed with 1. > > CAI Qian -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>