Date: Fri, 12 Nov 2021 16:19:04 +0000 From: Jessica Clarke <jrtc27@freebsd.org> To: Randall Stewart <rrs@FreeBSD.org> Cc: "src-committers@freebsd.org" <src-committers@FreeBSD.org>, "dev-commits-src-all@freebsd.org" <dev-commits-src-all@FreeBSD.org>, "dev-commits-src-main@freebsd.org" <dev-commits-src-main@FreeBSD.org> Subject: Re: git: b8d60729deef - main - tcp: Congestion control cleanup. Message-ID: <DDB6E732-7054-4C57-ADFD-4534CBAD5109@freebsd.org> In-Reply-To: <202111111131.1ABBVH6s017371@gitrepo.freebsd.org> References: <202111111131.1ABBVH6s017371@gitrepo.freebsd.org>
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On 11 Nov 2021, at 11:31, Randall Stewart <rrs@FreeBSD.org> wrote: >=20 > The branch main has been updated by rrs: >=20 > URL: = https://cgit.FreeBSD.org/src/commit/?id=3Db8d60729deefa0bd13e6a395fcab4928= e6e10445 >=20 > commit b8d60729deefa0bd13e6a395fcab4928e6e10445 > Author: Randall Stewart <rrs@FreeBSD.org> > AuthorDate: 2021-11-11 11:28:18 +0000 > Commit: Randall Stewart <rrs@FreeBSD.org> > CommitDate: 2021-11-11 11:28:18 +0000 >=20 > tcp: Congestion control cleanup. >=20 > NOTE: HEADS UP read the note below if your kernel config is not = including GENERIC!! >=20 > This patch does a bit of cleanup on TCP congestion control modules. = There were some rather > interesting surprises that one could get i.e. where you use a = socket option to change > from one CC (say cc_cubic) to another CC (say cc_vegas) and you = could in theory get > a memory failure and end up on cc_newreno. This is not what one = would expect. The > new code fixes this by requiring a cc_data_sz() function so we can = malloc with M_WAITOK > and pass in to the init function preallocated memory. The CC init = is expected in this > case *not* to fail but if it does and a module does break the > "no fail with memory given" contract we do fall back to the CC that = was in place at the time. >=20 > This also fixes up a set of common newreno utilities that can be = shared amongst other > CC modules instead of the other CC modules reaching into newreno = and executing > what they think is a "common and understood" function. Lets put = these functions in > cc.c and that way we have a common place that is easily findable by = future developers or > bug fixers. This also allows newreno to evolve and grow support for = its features i.e. ABE > and HYSTART++ without having to dance through hoops for other CC = modules, instead > both newreno and the other modules just call into the common = functions if they desire > that behavior or roll there own if that makes more sense. >=20 > Note: This commit changes the kernel configuration!! If you are not = using GENERIC in > some form you must add a CC module option (one of CC_NEWRENO, = CC_VEGAS, CC_CUBIC, > CC_CDG, CC_CHD, CC_DCTCP, CC_HTCP, CC_HD). You can have more than = one defined > as well if you desire. Note that if you create a kernel = configuration that does not > define a congestion control module and includes INET or INET6 the = kernel compile will > break. Also you need to define a default, generic adds 'options = CC_DEFAULT=3D\"newreno\" > but you can specify any string that represents the name of the CC = module (same names > that show up in the CC module list under net.inet.tcp.cc). If you = fail to add the > options CC_DEFAULT in your kernel configuration the kernel build = will also break. Not doing so breaks tinderbox, as well as configs not hooks up to tinderbox. I don=E2=80=99t think this is acceptable. Jess
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