On Sat, Feb 12, 2005 at 01:54:26PM -0200, Marcelo Tosatti wrote: > On Sat, Feb 12, 2005 at 12:17:25PM +0100, Andi Kleen wrote: > > Ray Bryant <[EMAIL PROTECTED]> writes: > > > set of pages associated with a particular process need to be moved. > > > The kernel interface that we are proposing is the following: > > > > > > page_migrate(pid, va_start, va_end, count, old_nodes, new_nodes); > > > > [Only commenting on the interface, haven't read your patches at all] > > > > This is basically mbind() with MPOL_F_STRICT, except that it has a pid > > argument. I assume that's for the benefit of your batch scheduler. > > As far as I understand mbind() is used to set policies to given memory > regions, not move memory regions? > > > But it's not clear to me how and why the batch scheduler should know about > > virtual addresses of different processes anyways. Walking > > /proc/pid/maps? That's all inherently racy when the process is doing > > mmap in parallel. The only way I can think of to do this would be to > > check for changes in maps after a full move and loop, but then you risk > > livelock. > > True. > > There is no problem, however, if all threads beloging to the process are > stopped, > as Ray mentions. > > So, there wont be memory mapping changes happening at the same time. > > Note that the memory migration code which sys_page_migrate() uses moves > running processes to other memory zones, handling truncate, etc. > > > And you cannot also just specify va_start=0, va_end=~0UL because that > > would make the node arrays grow infinitely. > > > > Also is there a good use case why the batch scheduler should only > > move individual areas in a process around, not the full process? > > Quoting him: > > "In addition to its use by batch schedulers, we also envision that > this facility could be used by a program to re-arrange the allocation > of its own pages on various nodes of the NUMA system, most likely > to optimize performance of the application during different phases > of its computation." > > Seems doable. > > Are there any good xamples of optimizations that could be made by > moving pages around except for NUMA?
If you have virtually indexed caches moving pages around can optimize cache behaviour if program access pattern is well known? That is not a thing common thing to do - and is architecture dependant anyway. - 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/
