From: "Ilpo Järvinen" <[EMAIL PROTECTED]> Subject: [RFC PATCH] [TCP]: Fix lost_retrans loop vs fastpath problems Date: Tue, 9 Oct 2007 15:20:01 +0300
> Detection implemented with lost_retrans must work also when > fastpath is taken, yet most of the queue is skipped including > (very likely) those retransmitted skb's we're interested in. > This problem appeared when the hints got added, which removed > a need to always walk over the whole write queue head. > Therefore decicion for the lost_retrans worker loop entry must > be separated from the sacktag processing more than it was > necessary before. > > It turns out to be problematic to optimize the worker loop > very heavily because ack_seqs of skb may have a number of > discontinuity points. Maybe similar approach as currently is > implemented could be attempted but that's becoming more and > more complex because the trend is towards less skb walking > in sacktag marker. > > Maybe after(highest_sack_end_seq, tp->high_seq) checking is not > sufficiently accurate and causes entry too often in no-work-to-do > cases. Since that's not known, I've separated solution to that > from this patch. > > Noticed because of report against a related problem from TAKANO > Ryousei <[EMAIL PROTECTED]>. He also provided a patch to > that part of the problem. This patch includes solution to it > (though this patch has to use somewhat different placement). > TAKANO's description and patch is available here: > > http://marc.info/?l=linux-netdev&m=119149311913288&w=2 > > ...In short, TAKANO's problem is that end_seq the loop is using > not necessarily the largest SACK block's end_seq because the > current ACK may still have higher SACK blocks which are later > by the loop. > Thanks Ilpo! I am trying to evaluate this patch. But, I got a kernel panic at net_rx_action() in our experimental setting. I am using the net-2.6.24 kernel _without_ this patch. (I will post a bug report separately). Anyway, I will report the result as soon as possible. Ryousei Takano - 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
