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Message-ID: <20090116065107.GA4170@ff.dom.local> Date: Fri, 16 Jan 2009 06:51:08 +0000 From: Jarek Poplawski <jarkao2@...il.com> To: Willy Tarreau <w@....eu> Cc: David Miller <davem@...emloft.net>, herbert@...dor.apana.org.au, zbr@...emap.net, dada1@...mosbay.com, ben@...s.com, mingo@...e.hu, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, jens.axboe@...cle.com Subject: Re: [PATCH] tcp: splice as many packets as possible at once On Fri, Jan 16, 2009 at 12:44:08AM +0100, Willy Tarreau wrote: > On Fri, Jan 16, 2009 at 12:42:55AM +0100, Willy Tarreau wrote: > > On Thu, Jan 15, 2009 at 03:34:49PM -0800, David Miller wrote: > > > From: Herbert Xu <herbert@...dor.apana.org.au> > > > Date: Fri, 16 Jan 2009 10:32:05 +1100 > > > > > > > On Thu, Jan 15, 2009 at 03:26:08PM -0800, David Miller wrote: > > > > > +static inline struct page *linear_to_page(struct page *page, unsigned int len, > > > > > + unsigned int offset) > > > > > +{ > > > > > + struct page *p = alloc_pages(GFP_KERNEL, 0); > > > > > + > > > > > + if (!p) > > > > > + return NULL; > > > > > + memcpy(page_address(p) + offset, page_address(page) + offset, len); > > > > > > > > This won't work very well if skb->head is longer than a page. > > > > > > > > We'll need to divide it up into individual pages. > > > > > > Oh yes the same bug I pointed out the other day. > > > > > > But Willy can test this patch as-is, > > > > Hey, nice work Dave. +3% performance from your previous patch > > (31.6 MB/s). It's going fine and stable here. > > And BTW feel free to add my Tested-by if you want in case you merge > this fix. > > Willy > Herbert, good catch! David, if it's not too late I think more credits are needed, especially for Willy. He did "a bit" more than testing. Alas, I can't see this problem with skb->head longer than page. There is even some comment on this in __splice_segment(), but I can miss something. I'm more concerned with memory usage if these skbs are not acked for some reason. Isn't there some DOS issue possible? Thanks everybody, Jarek P. ---------> Based on a review by Changli Gao <xiaosuo@...il.com>: http://lkml.org/lkml/2008/2/26/210 Foreseen-by: Changli Gao <xiaosuo@...il.com> Diagnosed-by: Willy Tarreau <w@....eu> Reported-by: Willy Tarreau <w@....eu> Fixed-by: Jens Axboe <jens.axboe@...cle.com> Signed-off-by: Jarek Poplawski <jarkao2@...il.com> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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