Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: > > - if (limit > sk->sk_sndbuf) > > - limit = sk->sk_sndbuf; > > + /* Don't limit to ALG_MAX_PAGES if the pages are all already pinned. */ > > + if (!user_backed_iter(&msg->msg_iter)) > > + max_pages = INT_MAX; If the iov_iter is a kernel-backed type (BVEC, KVEC, XARRAY) then (a) all the pages it refers to must already be pinned in memory and (b) the caller must have limited it in some way (splice is limited by the pipe capacity, for instance). In which case, it seems pointless taking more than one pass of the while loop if we can avoid it - at least from the point of view of memory handling; granted there might be other criteria such as hogging crypto offload hardware. > > + else > > + max_pages = min_t(size_t, max_pages, > > + DIV_ROUND_UP(sk->sk_sndbuf, PAGE_SIZE)); > > What's the purpose of relaxing this limit? If the iov_iter is a user-backed type (IOVEC or UBUF) then it's not relaxed. max_pages is ALG_MAX_PAGES here (actually, I should just move that here so that it's clearer). I am, however, applying the sk_sndbuf limit here also - there's no point extracting more pages than we need to if ALG_MAX_PAGES of whole pages would overrun the byte limit. > Even if there is a reason for this shouldn't this be in a patch by itself? I suppose I could do it as a follow-on patch; use ALG_MAX_PAGES and sk_sndbuf before that as for user-backed iterators. Actually, is it worth paying attention to sk_sndbuf for kernel-backed iterators? David
