On Thu, 6 Apr 2023 16:27:28 -0700 "T.J. Mercier" <tjmercier@xxxxxxxxxx> wrote: > > When you say "decide what's the largest reasonable size", I think it > > is difficult as with the variety of RAM sizes and buffer sizes I don't > > think there's a fixed limit. Systems with more ram will use larger > > buffers for image/video capture buffers. And yes, you're right that > > ram/2-1 in a single allocation is just as broken, but I'm not sure how > > to establish a better guard rail. > > > > thanks > > -john > > I like ENOMEM with the len / PAGE_SIZE > totalram_pages() check and > WARN_ON. We know for sure that's an invalid request, and it's pretty > cheap to check as opposed to trying a bunch of reclaim before failing. Well, if some buggy caller has gone and requested eleventy bigabytes of memory, doing a lot of reclaiming before failing isn't really a problem - we don't want to optimize for this case! > For buffers smaller than that I agree with John in that I'm not sure > there's a definitive threshold. Well... why do we want to do _anything_ here? Why cater for buggy callers? I think it's because "dma-buf behaves really badly with very large allocation requests". Again, can we fix that instead?
