12 ms·
Curl HTTP/3 Performance
- hlandau 3y agoAuthor of the OpenSSL QUIC stack here. Great writeup. TBQH, I'm actually really pleased with these performance figures - we haven't had time yet to do this kind of profiling or make any optimisations. So what we're seeing here is the performance prior to any kind of concerted measurement or optimisation effort on our part. In that context I'm actually very pleasantly surprised at how close things are to existing, more mature implementations in some of these benchmarks. Of course there's now plenty of tuning and optimisation work to be done to close this gap.
- foofie 3y agoHow awesome is that? Thank you for all your harf work. It's thanks to people such as yourself that the whole world keeps on working. Obligatory: https://xkcd.com/2347/ https://xkcd.com/2347/
- apitman 3y agoI'm curious if you've architected it in such a way that it lends itself to optimization in the future? I'd love to hear more about how these sorts of things are planned, especially in large C projects.
- hlandau 3y agoAs much as possible, yes. With something like QUIC "optimisation" breaks down into two areas: performance tuning in terms of algorithms, and tuning for throughput or latency in terms of how the protocol is used. The first part is actually not the major issue, at least in our design everything is pretty efficient and designed to avoid unnecessary copying. Most of the optimisation I'm talking about above is not about things like CPU usage but things like tuning loss detection, congestion control and how to schedule different types of data into different packets. In other words, a question of tuning to make more optimal decisions in terms of how to use the network, as opposed to reducing the execution time of some algorithm. These aren't QUIC specific issues but largely intrinsic to the process of developing a transport protocol implementation. It is true that QUIC is intrinsically less efficient than say, TCP+TLS in terms of CPU load. There are various reasons for this, but one is that QUIC performs encryption per packet, whereas TLS performs encryption per TLS record, where one record can be larger than one packet (which is limited by the MTU). I believe there's some discussion ongoing on possible ways to improve on this. There are also features which can be added to enhance performance, like UDP GSO, or extensions like the currently in development ACK frequency proposal.
- Matthias247 3y agoActually the benchmarks just measure the first part (cpu efficiency) since it’s a localhost benchmark. The gap will be most likely due to missing GSO if it’s not implemented. Its such a huge difference, and pretty much the only thing which can prevent QUIC from being totally inefficient.
- apitman 3y agoThank you for the details!
- benreesman 3y agoThank you kindly for your work. These protocols are critically important and more the more high-quality and open implementations exist the more likely they are to be free and inclusive. Also, hat tip for such competitive performance on an untuned implementation.
- spullara 3y agoAre there good reasons to use HTTP3/QUIC that aren't based on performance?
- Matthias247 3y agoWe need to distinguish between performance (throughput over a congested/lossy connection) and efficiency (cpu and memory usage). Quic can achieve higher performance, but will always be less efficient. The linked benchmark actually just measures efficiency since it’s about sending data over loopback on the same host
- jzwinck 3y agoWhat makes QUIC less efficient in CPU and memory usage?
- Matthias247 3y agoAmong others: having to transmit 1200-1500byte packets individually to the kernel, which it will all route, filter (iptables, nftables, ebpf) individually instead of just acting on much bigger data chunks for TCP. With GSO it gets a bit better, but it’s still far off from what can be done for TCP. Then there’s the userspace work for assembling and encrypting all these tiny packets individually, and looking up the right datastructures (connections, streams). And there’s challenges load balancing the load of multiple Quic connections or streams across CPU cores. If only one core dequeues UDP datagrams for all connections on an endpoint then those will be bottlenecked by that core - whereas for TCP the kernel and drivers can already do more work with multiple receive queues and threads. And while one can run multiple sockets and threads with port reuse, it poses other challenges if a packet for a certain connection gets routed to the wrong thread due to connection migration. Theres also solutions for that - eg in the form of sophisticated eBPF programs. But they require a lot of work and are hard to apply for regular users that just want to use QUIC as a library.
- drewg123 3y agoQuic throws away roughly 40 years of performance optimizations that operating systems and network card vendors have done for TCP. For example (based on the server side) - sendfile() cannot be done with QUIC, since the QUIC stack runs in userspace. That means that data must be read into kernel memory, copied to the webserver's memory, then copied back into the kernel, then sent down to the NIC. Worse, if crypto is not offloaded, userspace also needs to encrypt the data. - LSO/LRO are (mostly) not implemented in hardware for QUIC, meaning that the NIC is sent 1500b packets, rather than being sent a 64K packet that it segments down to 1500b. - The crypto is designed to prevent MiTM attacks, which also makes doing NIC crypto offload a lot harder. I'm not currently aware of any mainstream (eg, not an FPGA by a startup) that can do inline TLS offload for QUIC. There is work ongoing by a lot of folks to make this better. But at least for now, on the server side, Quic is roughly an order of magnitude less efficient than TCP. I did some experiments last year for a talk I gave which approximated loosing the optimizations above. https://people.freebsd.org/~gallatin/talks/euro2022.pdf https://people.freebsd.org/~gallatin/talks/euro2022.pdf For a video CDN type workload with static content, we'd go from being about to serve ~400Gb/s per single-core AMD "rome" based EPYC (with plenty of CPU idle) to less than 100Gb/s per server with the CPU maxed out. Workloads where the content is not static and has to be touched already in userspace, things won't be so comparatively bad.
- mgaunard 3y agoHTTP/1 remains the one with the highest bandwidth. No surprise here.
- BitPirate 3y agoIt's a bit like drag racing. If all you care about is the performance of a single transfer that doesn't have to deal with packet loss etc, HTTP/1 will win.
- varjag 3y agoIt runs over TCP, you don't need to deal with packet loss.
- vlovich123 3y agoWhat they’re suggesting is that under packet loss conditions QUIC will outperform TCP due to head of line blocking (particularly when there are multiple assets to fetch). Both TCP and QUIC abstract away packet loss but they have different performance characteristics under those conditions.
- BitPirate 3y agoThe performance difference between H1/H2 and H3 in this test doesn't really surprise me. The obvious part is the highly optimised TCP stack. But I fear that the benchmark setup itself might be a bit flawed. The biggest factor is the caddy version used for the benchmark. The quic-go library in caddy v2.6.2 lacks GSO support, which is crucial to avoid high syscall overhead. The quic-go version in caddy v2.6.2 also doesn't adjust UDP buffer sizes. The other thing that's not clear from the blog post is the network path used. Running the benchmark over loopback only would give TCP-based protocols an advantage if the QUIC library doesn't support MTU discovery.
- Etheryte 3y agoI don't think taking shots at the Caddy version being not the latest is a fair criticism to be honest. Version 2.6.2 was released roughly three months ago, so it's not like we're talking about anything severely outdated, most servers you run into in the wild will be running something older than that.
- zamadatix 3y agoI think you mixed up what year we're now :). Caddy 2.6.2 October 13, 2022 so it's been not 3 but 15 months since release. Even more relevantly, HTTP/3 was first supported out of the box in 2.6.0 - released Sep 20, 2022. Even if 2.6.2 had been just 3 months old that it's from the first 22 days of having HTTP/3 support out of the box instead of the versions from the following 3 months would definitely be relevant criticism to note. https://github.com/caddyserver/caddy/releases?page=2 https://github.com/caddyserver/caddy/releases?page=2
- francislavoie 3y agoThis is why I'm not a fan of debian. (I assume OP got that version from debian because I can't think of any other reason they wouldn't have used latest.) They packaged Caddy, but they never update at the rate we would reasonably expect. So users who don't pay attention to the version number have a significantly worse product than is currently available. We have our own apt repo which always has the latest version: https://caddyserver.com/docs/install#debian-ubuntu-raspbian https://caddyserver.com/docs/install#debian-ubuntu-raspbian
- nezirus 3y agoMaybe shout out to HAProxy people, like many they've observed performance problems with OpenSSL 3.x series. But having good old OpenSSL with QUIC would be so convenient for distro packages etc https://github.com/haproxy/wiki/wiki/SSL-Libraries-Support-Status https://github.com/haproxy/wiki/wiki/SSL-Libraries-Support-S...
- samueloph 3y agoNice write-up. I'm one of the Debian maintainers of curl and we are close to enabling http3 on the gnutls libcurl we ship. We have also started discussing the plan for enabling http3 on the curl CLI in time for the next stable release. Right now the only option is to switch the CLI to use the gnutls libcurl, but looks like it might be possible to stay with openssl, depending on when non-experimental support lands and how good openssl's implementation is.
- mistrial9 3y agomaybe the right time to clean up the unexpected and awkward set of libs that are currently installed, too ?
- pabs3 3y agoAny chance of WebSocket being enabled too?
- samueloph 3y agoThat's still an experimental feature on curl's side so I'm not sure. https://everything.curl.dev/helpers/ws/support https://everything.curl.dev/helpers/ws/support
- jgalt212 3y agoDoes Curl performance really matter? i.e. if it's too performant, doesn't that increase the odds your spider is blocked? Of course, if you're sharding horizontally across targets, then any performance increase is appreciated.
- j16sdiz 3y agolibcurl is the backend for many (RESTful) API library. Improving upload throughput to S3 bucket would be great, right?
- backum 3y ago[flagged]
- zamadatix 3y agoWhat if you're not using curl as a spider? Even if you are I'd recommend some other spider design which doesn't rely on the performance of curl to set the crawling rate.
- vitus 3y agoIt is promising to see that openssl-quic serial throughput is within 10-20% of more mature implementations such as quiche. (Which quiche, though? Is this Google's quiche, written in C++, or Cloudflare's quiche, written in Rust? It turns out that's approximately the only word that starts with "quic" that isn't a derivative of "quick".) One of QUIC's weaknesses is that it's known to be much less CPU efficient, largely due to the lack of things like HW offload for TLS. > Also, the HTTP/1.1 numbers are a bit unfair since they do run 50 TCP connections against the server. To emphasize this point: no modern browser will open 50 concurrent connections to the same server for 50 GET requests. You'll see connection pooling of, uh, 6 (at least for Chrome and Firefox), so the problems of head-of-line blocking that HTTP/2 and HTTP/3 attempt to solve would have manifested in more realistic benchmarks. Some questions I have: - What kind of CPU is in use? How much actual hw parallelism do you have in practice? - Are these requests actually going over the network (even a LAN)? What's the MTU? - How many trials went into each of these graphs? What are the error bars on these?
- jsty 3y agoLooks like Cloudflare quiche: https://github.com/curl/curl/blob/0f4c19b66ad5c646ebc3c4268a0f3ad9c15bf57c/docs/HTTP3.md?plain=1#L180 https://github.com/curl/curl/blob/0f4c19b66ad5c646ebc3c4268a...
- ndriscoll 3y ago> To emphasize this point: no modern browser will open 50 concurrent connections to the same server for 50 GET requests. They will. You just need to go bump that number in the settings. :-)
- pclmulqdq 3y agoHardware offload should be protocol-independent, but I suppose most network cards assume some stuff about TLS and aren't set up for QUIC?
- Matthias247 3y agoNICs assume stuff for TCP (segmentation offload) that they can’t do for UDP, or can only do in a very limited fashion (GSO). TLS offloads are very niche. There’s barely anyone using them in production, and the benchmarks are very likely without
- londons_explore 3y agoAnyone else disappointed that the figures for localhost are in MB/s not GB/s? The whole lot just seems an order of magnitude slower than I was hoping to see.
- zamadatix 3y agoA core of the 4770 (curl is single threaded) can't even manage a full order of magnitude more plain AES encryption throughput - ignoring it also has to be done into small packets and decrypted on the same machine.
- superkuh 3y agoCan cURL's HTTP/3 implementation work with self signed certs? Pretty much every other HTTP/3 lib used by major browsers do not. And since HTTP/3 does not allow for null cypher or TLS-less connections this means in order to establish an HTTP/3 connection a third party CA must be involved. As is right now it is impossible to host a HTTP/3 server visitable by a random person you've never met without a corporate CA continually re-approving your ability to. HTTP/3 is great for corporate needs but it'll be the death of the human web.
- adobrawy 3y agoGiven that browsers discourage HTTP traffic (warning that the connection is insecure), given how easily free SSL certificates are available, and given that HTTPS is already the standard on small hobbyist sites, I don't expect The requirement for an SSL certificate has been a blocker in HTTP/3 adoption.
- ndriscoll 3y agoDo browsers warn for http (beyond the address bar icon)? I don't think they ever have for my personal site. I also don't think you can really say there's a "standard" for how hobbyists do things. I'm definitely in the bucket of people who use http because browsers throw up scary warnings if you use a self-signed cert, and scary warnings aren't grandma friendly when I want to send photos of the kids. The benefit of TLS isn't worth setting up publicly signed certs to me, and I don't want to invite the extra traffic by appearing on a CT log. Like the other poster said, it all makes sense for the corporate web. Not so much for the human web. For humans, self-signed certs with automatic TOFU makes sense, but browsers are controlled by and made for the corporate web.
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- jrpelkonen 3y agoI really don’t want to criticize anyone or their hard work, and appreciate both curl and OpenSSL as a long time user. That said, I personally find it disappointing that in 2024 major new modules are being written in C. Especially so given that a) existing Quic modules written in Rust exist, and b) there’s a precedent for including Rust code in Curl. Of course there are legacy reasons for maintaining existing codebases, but what is it going to take to shift away from using C for greenfield projects?
- zinekeller 3y agoFor something like curl (which is also used in embedded systems: a legally-verified (compliant with ISO and other standards, for better or worse) Rust compiler that targets common microarchitectures is a definite first step. Fortunately, the first half of it exists (Ferrocene, https://ferrous-systems.com/ferrocene/ https://ferrous-systems.com/ferrocene/). The second one is harder: there are architectures even GCC does not target (these architectures rely on other compilers like the Small Device C Compiler (or a verified variant) or even a proprietary compiler), and LLVM only compiles to a subset of GCC. Even if there's a GCC Rust (currently being developed fortunately), you are still leaving a lot of architectures.
- jrpelkonen 3y agoThis is a good point: there are many niche architectures where Rust is not a viable option. But in this specific case, I don’t see these system benefiting from h3/Quic. HOL blocking etc. will rarely, if ever, be a limiting factor for the use cases involved.
- apitman 3y agoNot saying you're wrong, but it's worth noting that switching to Rust is not free. Binary sizes, language complexity, and compile times are all significantly larger.
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- teunispeters 3y ago
- throwaway892238 3y agoLol, wait, HTTP2 and HTTP1.1 both trounce HTTP3? Talk about burying the lede. Wasn't performance the whole point behind HTTP3? This chart shows that HTTP2 is more than half as slow as HTTP1.1, and HTTP3 is half as slow as HTTP2. Jesus christ. If these get adopted across the whole web, the whole web's performance could get up to 75% slower . That's insane. There should be giant red flags on these protocols that say "warning: slows down the internet"
- CharlesW 3y ago> Wasn't performance the whole point behind HTTP3? Faster, more secure, and more reliable, yes. The numbers in this article looks terrible, but real-world testing¹ shows that real-world HTTP/3 performance is quite good, even though implementations are relatively young. "…we saw substantially higher throughput on HTTP/3 compared to HTTP/2. For example, we saw about 69% of HTTP/3 connections reach a throughput of 5 Mbps or more […] compared to only 56% of HTTP/2 connections. In practice, this means that the video streams will be of a higher visual quality, and/or have fewer stalls over HTTP/3." ¹https://pulse.internetsociety.org/blog/measuring-http-3-real-world-performance https://pulse.internetsociety.org/blog/measuring-http-3-real...
- zamadatix 3y agoIf the last decade of web protocol development seems backwards to you after reading one benchmark then why immediately assume it's insane and deserves a warning label instead of asking why your understanding doesn't match your expectations? The benchmark meant to compare how resource efficient the new backend for curl is by using localhost connectivity. By using localhost connectivity any real world network considerations (such as throughput discovery, loss, latency, jitter, or buffering) are sidestepped to allow a direct measurement of how fast the backend alone is. You can't then assume those numbers have a meaningful direct extrapolation to the actual performance of the web because you don't know how the additional things the newer protocols do impact performance once you add a real network. Ingoring that, you still have to consider the notes like "Also, the HTTP/1.1 numbers are a bit unfair since they do run 50 TCP connections against the server." before making claims about HTTP2 being more than half as slow as HTTP1.1.
- apitman 3y agoVery nice. I would love to see some numbers including simulated packet loss. That's theoretically an area h3 would have an advantage.
- jupp0r 3y agoGreat writeup, but the diagrams are downright awful. I'd separate the different facets visually to make it easier to see the difference vs those different colors.
- 1vuio0pswjnm7 3y agoWould it be worthwhile to test QUIC using some other TLS library besides OpenSSL, e.g., wolfSSL. I think I read that the the cURL author is working with them, or for them. Apologies if this is incorrect.