Date: Fri, 8 Jan 2016 13:22:45 -0800 From: NGie Cooper <yaneurabeya@gmail.com> To: Gleb Smirnoff <glebius@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r293439 - in head: lib/libc/sys sys/dev/ti sys/kern sys/sys usr.bin/netstat Message-ID: <88B48C42-DFEF-4CAE-973E-BDF2A408B4A3@gmail.com> In-Reply-To: <20160108211041.GG1906@FreeBSD.org> References: <201601082034.u08KYvLv075281@repo.freebsd.org> <96B980EE-FD2F-490E-BA5E-4F23A67CEB18@gmail.com> <20160108211041.GG1906@FreeBSD.org>
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> On Jan 8, 2016, at 13:10, Gleb Smirnoff <glebius@FreeBSD.org> wrote: >=20 > On Fri, Jan 08, 2016 at 12:44:32PM -0800, NGie Cooper wrote: > N> > Log: > N> > New sendfile(2) syscall. A joint effort of NGINX and Netflix = from 2013 and > N> > up to now. > N> >=20 > N> > The new sendfile is the code that Netflix uses to send their = multiple tens > N> > of gigabits of data per second. The new implementation features = asynchronous > N> > I/O, when I/O operations are launched, but not awaited to be = complete. An > N> > explanation of why such behavior is beneficial compared to old = one is > N> > going to be too long for a commit message, so we will skip it = here. > N> >=20 > N> > Additional features of new syscall are extra flags, which = provide an > N> > application more control over data sent. The SF_NOCACHE flag = tells > N> > kernel that data shouldn't be cached after it was sent. The = SF_READAHEAD() > N> > macro allows to specify readahead size in pages. > N> >=20 > N> > The new syscalls is a drop in replacement. No modifications are = required > N> > to applications. One can take nginx binary for stable/10 and run = it > N> > successfully on head. Although SF_NODISKIO lost its original = sense, as now > N> > sendfile doesn't block, and now means something completely = different (tm), > N> > using the new sendfile the old way is absolutely safe. > N> >=20 > N> > Celebrates: Netflix global launch! > N> > Sponsored by: Nginx, Inc. > N> > Sponsored by: Netflix > N> > Relnotes: yes > N>=20 > N> Did anyone review these changes and the other changes made recently = to sys/kern and sys/net* ? >=20 > 1) The review requests were sent continuosly to arch@ during last 1.5 = years. >=20 > = https://lists.freebsd.org/pipermail/freebsd-arch/2014-May/015385.html >=20 > 2) Team of engineers at Netflix has a lot of code build on top of that = code, > e.g. SSL_sendfile(). Of course, writing something on top assumes = reviewing, > so assume it reviewed thoroughly by rrs@. Actually, here is list of = people > who did some review of the code: emax@, rrs@, scottl@, gallatin@, = imp@. >=20 > 3) Do you have any particulars concerns with this change or those made = recently > to sys/kern and sys/net*? I don=E2=80=99t as of right now, other than it=E2=80=99s really = difficult to audit changes and assess risk if someone doesn=E2=80=99t = have access to the CRs :(. Also=E2=80=A6 N> > An N> > explanation of why such behavior is beneficial compared to old one = is N> > going to be too long for a commit message, so we will skip it = here. This wasn=E2=80=99t really helpful. It would have been nice if there was = a wiki page or some other reference used in this commit which would have = described the where, why, and how behind this change a lot more. Thanks, -NGie=
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