On Thu, May 17, 2018 at 03:37:21PM -0400, Sinan Kaya wrote: > On 5/17/2018 2:18 PM, Matthew Wilcox wrote: > > On Thu, May 17, 2018 at 01:36:19PM -0400, Sinan Kaya wrote: > >> Try to keep the pool closer to the device's NUMA node by changing kmalloc() > >> to kmalloc_node() and devres_alloc() to devres_alloc_node(). > > Have you measured any performance gains by doing this? The thing is that > > these allocations are for the metadata about the page, and the page is > > going to be used by CPUs in every node. So it's not clear to me that > > allocating it on the node nearest to the device is going to be any sort > > of a win. > > > > It is true that this is metadata but it is one of the things that is most > frequently used in spite of its small size. > > I don't think it makes any sense to cross a chip boundary for accessing a > pointer location on every single pool allocation. > > Remember that the CPU core that is running this driver is most probably on > the same NUMA node as the device itself. Umm ... says who? If my process is running on NUMA node 5 and I submit an I/O, it should be allocating from a pool on node 5, not from a pool on whichever node the device is attached to. If it actually makes a performance difference, then NVMe should allocate one pool per queue, rather than one pool per device like it currently does. > Also, if it was a one time init kind of thing, I'd say "yeah, leave it alone". > DMA pool is used by a wide range of drivers and it is used to allocate > fixed size buffers at runtime. * DMA Pool allocator * * Copyright 2001 David Brownell * Copyright 2007 Intel Corporation * Author: Matthew Wilcox <willy@xxxxxxxxxxxxxxx> I know what it's used for.
