Date: Fri, 8 Jan 2021 19:46:10 -0500 From: Andrew Gallatin <gallatin@cs.duke.edu> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: freebsd-arch@freebsd.org, Rick Macklem <rmacklem@uoguelph.ca>, Allan Jude <allanjude@freebsd.org> Subject: Re: Should we enable KERN_TLS on amd64 for FreeBSD 13? Message-ID: <10fb8ede-b8cf-645c-ceee-a9cb3f9fe39f@cs.duke.edu> In-Reply-To: <20210108202256.GA7669@troutmask.apl.washington.edu> References: <8eff83e5-49bc-d410-626e-603c03877b80@cs.duke.edu> <20210108202256.GA7669@troutmask.apl.washington.edu>
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On 1/8/21 3:22 PM, Steve Kargl wrote: > On Fri, Jan 08, 2021 at 12:26:38PM -0500, Andrew Gallatin wrote: >> >> Kernel TLS (KTLS) support was added roughly a year ago, and provides >> an efficient software or hardware accelerated path to have the kernel >> (or the NIC) handle TLS crypto. This is quite useful for web and >> NFS servers, and provides a huge (2x -> 5x) efficiency gain by >> avoiding data copies into userspace for crypto, and potentially >> offloading the crypto to hardware. >> >> KTLS is well tested on amd64, having been used in production at Netflix >> for nearly 4 years. The vast majority of Netflix video has been served >> via KTLS for the last few years. Its what has allowed us to serve >> 100Gb/s on Xeon 2697A cpus for years, and what allows us to serve >> nearly 400Gb/s on AMD servers with NICs which support crypto offload. >> >> I have received a few requests to enable it by default in GENERIC, and >> I'd like to get some opinions. >> >> There are essentially 3 options >> >> 1) Fully enable KTLS by adding 'options KERN_TLS' to GENERIC, and >> flipping kern.ipc.tls.enable=1 >> >> The advantage of this is that it "just works" out of the box for users, >> and for reviewers. >> >> The drawback is that new code is thrust on unsuspecting users, >> potentially exposing them to bugs that we have not found in our >> somewhat limited web serving workload. >> >> 2) Enable KTLS in GENERIC, but leave it turned off by default. >> >> This option allows users to enable ktls without a rebuild of GENERIC, >> but does not enable it by default. So they can enable it if they >> know about it, but are protected from bugs. >> >> The disadvantages of this are that it increases the kernel size >> by ~20K, starts up one thread per core on every amd64 machine, >> and it adds more required tuning to get good performance from FreeBSD. >> >> >> 3) Continue along with KTLS disabled in GENERIC >> >> This is the lowest risk, but adds a higher bar for users wanting >> to use ktls. >> > > Drew, > > For those that use a custom kernel configuration, would we need > to add 'options KERN_TLS' to our config files, or can a module > be loaded from the boot loader (ie. via /boot/loader.conf)? > > I have no preference between 1 or 2, either seems acceptable to > me for those running the bleeding edge. > Its not as simple as just loading a module, you'd need to have options KERN_TLS in your kernel config. There are a few places in the kernel with ifdefs for KERN_TLS (sendfile, and sockets, for example). Thank you for the feedback! Drew
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