> On May 7, 2017, at 5:38 AM, Andy Lutomirski <luto@xxxxxxxxxx> wrote: > > As I've been working on polishing my PCID code, a major problem I've > encountered is that there are too many x86 TLB flushing code paths and > that they have too many inconsequential differences. The result was > that earlier versions of the PCID code were a colossal mess and very > difficult to understand. > > This series goes a long way toward cleaning up the mess. With all the > patches applied, there is a single function that contains the meat of > the code to flush the TLB on a given CPU, and all the tlb flushing > APIs call it for both local and remote CPUs. > > This series should only adversely affect the kernel in a couple of > minor ways: > > - It makes smp_mb() unconditional when flushing TLBs. We used to > use the TLB flush itself to mostly avoid smp_mb() on the initiating > CPU. > > - On UP kernels, we lose the dubious optimization of inlining nerfed > variants of all the TLB flush APIs. This bloats the kernel a tiny > bit, although it should increase performance, since the SMP > versions were better. > > Patch 10 in here is a little bit off topic. It's a cleanup that's > also needed before PCID can go in, but it's not directly about > TLB flushing. > > Thoughts? In general I like the changes. I needed to hack Linux TLB shootdowns for a research project just because I could not handle the code otherwise. I ended up doing some of changes that you have done. I just have two general comments: - You may want to consider merging the kernel mappings invalidation with the userspace mappings invalidations as well, since there are still code redundancies. - Don’t expect too much from concurrent TLB invalidations. In many cases the IPI latency dominates the overhead from my experience. Regards, Nadav -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href
