On (03/24/15 09:36), Benjamin Herrenschmidt wrote: > > - One pool only > > - Whenever the allocation is before the previous hint, do a flush, that > should only happen if a wrap around occurred or in some cases if the > device DMA mask forced it. I think we always update the hint whenever we > successfully allocate from the small pools. right, I believe this is close to what I discussed in the previous thread, and approx what I have in patchv5, except that the flush indirection can be passed as a function pointer, or via the table_ops. > > - Deal with the largealloc case. That's the contentious issue, see > below. : > The largealloc issue is a different can of worms. We can try adding an > option to disable the largealloc business completely (instead of hard > wiring the "15", make that a variable and define that 0 means no > largealloc pool). What I've tried to do is to have a bool large_pool arg passed to iommu_tbl_pool_init. In my observation (instrumented for scsi, ixgbe), we never allocate more than 4 pages at a time, so I pass in large_pool == false for all the sparc platforms. > Or we can decide that large allocs are rare (typically > pci_alloc_consistent, ie, driver init time), and thus always flush on > them (or rather on free of a large chunk). David, what's your take > there ? I have a feeling that should work fine without a noticeable > performance issue... > > I would also keep a "dirty" flag set on any free and cleared on any > flush to avoid more spurrious flushes, but here too the benefit might be > in the noise. -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
