On Sat, Sep 10, 2022 at 03:35:45PM +0300, Serge Semin wrote: > On Sat, Sep 10, 2022 at 07:30:45AM +0200, Christoph Hellwig wrote: > > I think this will work, but unless we have to I'd generally prefer > > to just split dta that is DMAed into into a separate allocation. > > That is, do a separate kmalloc for the nvme_smart_log structure. > > Well, both approaches will solve the denoted problem. I am just > wondering why do you think that the kmalloc-ed buffer is more > preferable? IMO it is a bit less suitable since increases the memory > granularity - two kmalloc's instead of one. Moreover it makes the code ^ `-- I meant fragmentation of course... > a bit more complex for the same reason of having two mallocs and two > frees. Meanwhile using the ____cacheline_aligned qualifier to prevent > the noncoherent DMA problem is a standard approach. > > What would be the best solution if we had a qualifier like this: > #ifdef CONFIG_DMA_NONCOHERENT > #define ____dma_buffer ____cacheline_aligned > #else > #define ____dma_buffer > #endif > and used it instead of the direct ____cacheline_aligned utilization. > > -Sergey > > > > > Guenter, is this ok with you?
