On Tue, 15 Mar 2011 14:35:47 +1030 Christopher Yeoh <cyeoh@xxxxxxxxxxx> wrote: > Hi Andrew, > > I was wondering if you thought the cross memory attach patch is in > suitable shape to go into your tree with view of getting it into > mainline sometime in the not too distant future. It looks reasonable to me, but I might have missed something and would ask that some of the other guys take a close look, please. It's regrettable that vmsplice() won't serve the purpose but I can see that the blocking problems are there. Minor thing: mm/memory.c is huge, and I think this new code would live happily in a new mm/process_vm_access.c. > There are some cases of MPI collectives where even a single copy > interface does not get us the performance gain we could. For example > in an MPI_Reduce rather than copy the data from the source we would > like to instead use it directly in a mathops (say the reduce is doing a > sum) as this would save us doing a copy. We don't need to keep a copy > of the data from the source. I haven't implemented this, but I think > this interface could in the future do all this through the use of the > flags - eg could specify the math operation and type and the kernel > rather than just copying the data would apply the specified operation > between the source and destination and store it in the destination. Well yes. This smells like MAP_SHARED. Thinking out loud: if we had a way in which a process can add and remove a local anonymous page into pagecache then other processes could access that page via mmap. If both processes map the file with a nonlinear vma they they can happily sit there flipping pages into and out of the shared mmap at arbitrary file offsets. The details might get hairy ;) We wouldn't want all the regular mmap semantics of making pages dirty, writing them back, etc so make that mmap be backed by a new special device rather than by a regular file, perhaps. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>