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Florian Westphal says: ==================== tcp: remove prequeue and header prediction During a hallway discussion with Eric Dumazet at Netdev 1.2 in Tokyo some maybe-not-so-useful-anymore TCP stack features came up, among these header prediction and prequeueing. In brief, TCP prequeue assumes a single-process-blocking-read design, which is not that common anymore. The most frequently used high-performance networking program that is an excellent fit for these features is netperf. The idea behind prequeueing is to move part of tcp processing, including retransmit queue cleaning, to process context. With (e)poll designs, prequeue is always skipped, so for such programs this is dead-code removal. Header prediction is also less useful nowadays. For packet trains, GRO will do packet aggregation so we do not get the per-packet benefit that this had before GRO anymore. Because of SACK, header prediction also will be ineffective once a connection suffers even light packet losses. code removal aside, after this change processing always occurs in BH context, this allows to experiment e.g. with doing bulk freeing of skb heads when incoming ACKs clean packets from the retransmit queue. There are no changes since the RFC, except in last patch (i missed another no-longer-used mib counter). I also edited a few commit messages. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.