From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy Polyakov Subject: Re: [PATCH][RFC] network splice receive Date: Tue, 12 Jun 2007 15:29:51 +0400 Message-ID: <20070612112950.GA16477@2ka.mipt.ru> References: <20070608074823.GG7341@kernel.dk> <20070608.010629.52902577.davem@davemloft.net> <20070608083853.GH7341@kernel.dk> <20070608085620.GC11488@2ka.mipt.ru> <20070608090439.GK7341@kernel.dk> <20070608135819.GA14302@2ka.mipt.ru> <20070608141452.GR7341@kernel.dk> <20070608145724.GA14561@2ka.mipt.ru> <20070608153011.GA2375@2ka.mipt.ru> <20070609063608.GX7341@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Cc: David Miller , netdev@vger.kernel.org To: Jens Axboe Return-path: Received: from relay.2ka.mipt.ru ([194.85.82.65]:42743 "EHLO 2ka.mipt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753423AbXFLLaI (ORCPT ); Tue, 12 Jun 2007 07:30:08 -0400 Content-Disposition: inline In-Reply-To: <20070609063608.GX7341@kernel.dk> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sat, Jun 09, 2007 at 08:36:09AM +0200, Jens Axboe (jens.axboe@oracle.com) wrote: > On Fri, Jun 08 2007, Evgeniy Polyakov wrote: > > On Fri, Jun 08, 2007 at 06:57:25PM +0400, Evgeniy Polyakov (johnpol@2ka.mipt.ru) wrote: > > > I will try some things for the nearest 30-60 minutes, and then will move to > > > canoe trip until thuesday, so will not be able to work on this idea. > > > > Ok, replacing in fs/splice.c every page_cache_release() with > > static void splice_page_release(struct page *p) > > { > > if (!PageSlab(p)) > > page_cache_release(p); > > } > > Ehm, I don't see why that should be necessary. Except in > splice_to_pipe(), I have considered that we need to pass in a release > function if mapping fails at some point. But it's probably best to do > that in the caller, since they have the knowledge of how to release the > pages. > > The rest of the PageSlab() tests are bogus. I had a crashdump, where page was released via splice_to_pipe() indeed, I did not investigate if it is possible to release provided page in other places. I think if in future there will other slab usage cases except networking receiving, that might be useful, but as is it is not needed. > > and putting cloned skb into private field instead of > > original on in spd_fill_page() ends up without kernel hung. > > Why? Seems pointless to allocate a clone just to hold on to the skb, a > reference should be equally good. I would not be opposed to doing it > this way, I just don't see what a clone buys us as compared to just > holding that reference to the skb. Receiving code does not expect shared skbs - too many fields are changed with assumptions that it is a private copy. > > I'm not sure it is correct, that page can be released in fs/splice.c > > without calling any callback from network code, when network data is > > being processed. > > Please explain! I had a crashdump, where page was attempted to be released in fs/splice.c:splice_to_pipe(), I do not have details handy, but the best solution would be to provide a release callback and use that instead of page_cache_release(). -- Evgeniy Polyakov