Date: Mon, 22 Mar 2004 11:31:37 -0500 (EST) From: Robert Watson <rwatson@FreeBSD.org> To: current@FreeBSD.org Subject: HEADS UP: debug.mpsafenet behavior changing! (turn it off) Message-ID: <Pine.NEB.3.96L.1040322112622.69952D-100000@fledge.watson.org>
next in thread | raw e-mail | index | archive | help
This is an advance HEADS UP. Over the next two weeks, I'm going to start merging more significant parts of the network locking patches. The first change is that the definition of debug.mpsafenet is going to chang. Up until now, this tunable has meant: If set, don't hold Giant over the lower levels of the network stack and IP forwarding path. If unset, Giant is held over the lower level parts of the stack. This provided substantial performance benefits on SMP and UP for forwarding and filtering, but not for locally sourced or sinked network traffic (as it didn't release Giant higher in the stack). As we push Giant off the higher levels of the stack, we will be changing how debug.mpsafenet works. Here's the new definition: If set, don't hold Giant over any of the network stack, including the sockets layer. If unset, Giant is held over all parts of the network stack. It's likely few people are running with debug.mpsafenet; however, if you are, this is your warning that you'll probably want to stop running with it shortly. With this change, we will be migrating to a dual-mode stack, in which you can either run the whole thing with Giant, or none of it. This approach is substantially easier to implement than a mixed mode stack, in which some pieces are covered with Giant running side by side with other pieces that are not. During the migration period to fine-grained locking (as patches are merged, etc), it will likely be a very bad idea to run with this tunable set, so turn it off now! debug.mpsafenet will continue to exist for the forseeable future in some form, as it will allow non-MPSAFE network stack components to continue to function, at the cost of performance. In the next few days, I will be posting pretty large patchsets to arch@ and requesting review and testing. I'll commit a note to UPDATING with similar but abbreviated content. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Senior Research Scientist, McAfee Research
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.NEB.3.96L.1040322112622.69952D-100000>