Many thanks to Marty, Wei-Keng, Tom and Andreas for their very helpful support (I hope I didn't leave anyone out!).
Thanks very much, and I think I can now address the problem. Phil On Fri, 9 May 2008, Tom.Wang wrote: > Hi, > > Andreas Dilger wrote: >> On May 09, 2008 09:41 -0400, Phil Dickens wrote: >> >>> I am having similar struggles with locking on MPI-IO. >>> I am doing a simple strided write, and it fails because >>> of the locking. I'm a bit behind in the discussion, but >>> is there a way to fix (workaround) this problem?? Is this >>> something in my code, or the default driver (this is on >>> lonestar at TACC)? I have even downloaded the most up to date >>> version of MPICH, which I believe has a new Lustre ADIO >>> driver, but I am running into the same issues. >>> >>> Any thoughts would be greatly appreciated!! >>> >> One possibility is to mount the clients with "-o localflock", leaving all >> of the locking internal to Lustre. This in essence provides single-node >> flock (i.e. coherent on that node, but not across all clients). The other >> alternative is "-o flock", which is coherent locking across all clients, >> but has a noticable performance impact and may affect stability, depending >> on the version of lustre being used (newer is better of course). >> >> I'm not positive of the internals of the MPI-IO code, whether it depends >> on flock providing a barrier across nodes, or if it does this only for >> e.g. NFS not keeping writes coherent so they don't clobber the same page >> when writing. >> >> Tom is the expert here... >> > It uses flock to keep the coherence of read-modify-write for data_sieving. > > You can use > > ierr = MPI_Info_create(&FILE_INFO_TEMPLATE); > > ............. > ierr = MPI_Info_set(FILE_INFO_TEMPLATE, "romio_ds_write", disable); > > to disable data_sieving in your application to avoid flock for stride_write. > > Thanks > WangDi >> >> > > > -- > Regards, > Tom Wangdi -- > Sun Lustre Group > System Software Engineer http://www.sun.com > _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
