From: Sridhar Samudrala <[EMAIL PROTECTED]> Date: Tue, 08 Aug 2006 10:19:51 -0700
> We cannot do this as xs_sendpages() doesn't like to use sendpage() > with highmem pages and has the following check before making the > actual call. > /* Hmm... We might be dealing with highmem pages */ > if (PageHighMem(*ppage)) > sendpage = sock_no_sendpage; > err = sendpage(sock, *ppage, base, len, flags); The question is why doesn't it "like" highmem pages? The kernel socket operation will handle highmem pages just fine and in fact this sock_no_sendpage bit in xs_sendpages() has a negative performance impact when it does trigger. What's more this code is even worse than it appears at first, because it will use sock_no_sendpage for _every_ page after the first highmem one it sees. I tried to figure out the origin of this highmem test. It comes from before all this code was moved from net/sunrpc/xdr.c into net/sunrpc/xprtsock.c Looking further in history, it even predates GIT :) So I went through the pre-GIT history and it shows that this test was there from the very beginning when xdr_sendpage and zerocopy sunrpc support was added. Trond, I think the highmem check in xs_sendpages() is completely bogus, do you mind if we remove it? :-) The socket layer will properly check the device to make sure it can handle highmem pages, and if not it will copy the data into a low-mem page as-needed. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
