On 2019-04-12 2:44 p.m., Bjorn Helgaas wrote: > On Wed, Apr 10, 2019 at 03:05:32PM -0600, Logan Gunthorpe wrote: >> Clean up the 'resource_alignment' parameter code to use kstrdup >> in the initcall routine instead of a static buffer that wastes memory >> regardless of whether the feature is used. This allows us to drop >> 'COMMAND_LINE_SIZE' bytes (typically 256-4096 depending on architecture) >> of static data. >> >> This is similar to what has been done for the 'disable_acs_redir' >> parameter. >> >> This conversion also allows us to use RCU instead of the spinlock to >> deal with the concurrency issue which further reduces memory usage. > > I'm unconvinced about this part. Spinlocks are CS 101 material and > I'm a little hesitant to use a graduate-level technique like RCU in a > case where it doesn't really buy us much -- we don't need the > performance advantage and the size advantage seems minimal. But I'm > an RCU ignoramus and maybe need to be educated. That's a reasonable point. I didn't think it was that difficult and the kernel's RCU API is pretty straightforward. But I can resubmit later keeping the spinlock. You're right that it's not that big of a gain. >> As part of the clean up we also squash pci_get_resource_alignment_param() >> into resource_alignment_show() and pci_set_resource_alignment_param() >> into resource_alignment_store() seeing these functions only had one >> caller and the show/store wrappers were needlessly thin. > > Squashing makes sense and would be nice as a separate patch. Ok, will do. Logan
