On Wednesday 14 November 2007 22:48, Herbert Xu wrote: > On Wed, Nov 14, 2007 at 03:10:22AM -0800, David Miller wrote: > > So the thing that's being effected here in TCP is > > net/ipv4/tcp.c:select_size(), specifically the else branch: > > Thanks for the pointer. Indeed there is a bug in that area. > I'm not sure whether it's causing the problem at hand but it's > certainly suboptimal. > > [TCP]: Fix size calculation in sk_stream_alloc_pskb
This looks like it fixes the problem! Still interested to know why SLAB didn't see the same thing... > We round up the header size in sk_stream_alloc_pskb so that > TSO packets get zero tail room. Unfortunately this rounding > up is not coordinated with the select_size() function used by > TCP to calculate the second parameter of sk_stream_alloc_pskb. > > As a result, we may allocate more than a page of data in the > non-TSO case when exactly one page is desired. > > In fact, rounding up the head room is detrimental in the non-TSO > case because it makes memory that would otherwise be available to > the payload head room. TSO doesn't need this either, all it wants > is the guarantee that there is no tail room. > > So this patch fixes this by adjusting the skb_reserve call so that > exactly the requested amount (which all callers have calculated in > a precise way) is made available as tail room. > > Signed-off-by: Herbert Xu <[EMAIL PROTECTED]> > > Cheers, - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
