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Date: Wed, 14 Nov 2007 15:46:16 -0800 (PST) From: David Miller <davem@...emloft.net> To: herbert@...dor.apana.org.au Cc: nickpiggin@...oo.com.au, clameter@....com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: 2.6.24-rc2: Network commit causes SLUB performance regression with tbench From: Herbert Xu <herbert@...dor.apana.org.au> Date: Wed, 14 Nov 2007 19:48:44 +0800 > [TCP]: Fix size calculation in sk_stream_alloc_pskb > > 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 <herbert@...dor.apana.org.au> Applied and I'll queue it up for -stable too. - 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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