On 6/28/24 5:47 PM, Kees Cook wrote: > On Thu, Jun 27, 2024 at 10:35:36PM -0700, Boqun Feng wrote: >> On Thu, Jun 20, 2024 at 10:43:39PM +0200, Vlastimil Babka wrote: >> > Rust people were asking about kmalloc alignment (but I forgot the details) >> >> It was me! The ask is whether we can specify the alignment for the >> allocation API, for example, requesting a size=96 and align=32 memory, >> or the allocation API could do a "best alignment", for example, >> allocating a size=96 will give a align=32 memory. As far as I >> understand, kmalloc() doesn't support this. > > I can drop the "align" argument. Do we want to hard-code a > per-cache-size alignment for the caches in a kmem_buckets collection?
I think you can drop it as a single value is really ill suited for a collection of different sizes. As for Rust's requirements we could consider whether to add a special flag if they use own bucket, or just implement the rules for non-power-of-two size globally. It should be feasible as I think in the non-debug caches it shouldn't in fact change the existing layout, which is the same situation as when we codified the power-of-two caches alignment as guaranteed.
