ELI5: Why does the GIL slow down CPU-bound multithreaded programs?

I understand why CPython needs the GIL: to prevent race conditions when counting references, which could cause memory leaks.

What I don't understand is:

  1. How do other high-level languages (like, say, Java) avoid this problem? Is it because Java uses garbage collection? Could Python discard the GIL by using garbage collection? Would that slow single-threaded performance? Why?

  2. Say you have a single process, multithreaded program. My understanding is that within this program, two threads cannot simultaneously execute instructions. In Python, I assume that rather than switch at the instruction level, threads must switch at the 'bytecode' level because of the GIL. Why is this a bad thing?

πŸ‘︎ 15
πŸ“°︎ r/learnpython
πŸ“…︎ Sep 23 2018
🚨︎ report
The future of Python is bright. Or is it?

You have seen the news.

Python is becoming the world’s most popular programming language :

- The Economist

- Stack Overflow Developers Survey 2018

- Stack Overflow Most Popular Languages 2017

However, Python still lacks important features for concurrency and functional programming.

For the concurrency, the Global Interpreter Locker impose heavy limits on the use of Python for cpu-bound multithreading.

For functional programming, even if Python is more functional than Java, it is still quite clear that it is not a language that treats well those who try a functional-first approach - and that is the will of its creator.

I think that Python cannot keep growing at this rate at the same time that it goes against these two very important trends. So I would like to know your opinion in this subject:

- Will next versions implement features that make Python more efficient for concurrency and more functional-friendly?

- Will a new pythonic language emerge that will implement these features (just like Scala is a concurrency and functional-friendly Java) ?

πŸ‘︎ 3
πŸ“°︎ r/Python
πŸ‘€︎ u/retep_kram
πŸ“…︎ Aug 08 2018
🚨︎ report
Apple M2 removes Intel Core i9-12950HX as PassMark's laptop CPU single-thread champion but trails behind Alder Lake-P in multithread benchmarking notebookcheck.net/Apple-M…
πŸ‘︎ 2
πŸ“°︎ r/realtech
πŸ‘€︎ u/rtbot2
πŸ“…︎ Aug 01
🚨︎ report
Very low multithreaded CPU-Z performance on an i5 12400F

Brand new build. B660M Aorus Pro AX DDR4, 2x8GB 3600MHz Corsair Vengeance LPX C18.

Single thread performance is a tad low (high 600s instead of around 700) but within single digit percentage points. Multicore is abysmal. I'm seeing scores just shy of 1600 when the expected result should be just shy of 5000.

I've run memtest86 with no errors for 6 passes at XMP settings. I'm going to update the bios, but from what I've read, a bios update on this MOBO should only have a dramatic impact on the non-F sku of this CPU.

CPU usage was allegedly 100% during the test on all cores during the all core portion of the benchmark, temps were in the high 50s, but power consumption never went above about 45W or so.

Any ideas what's going on?

πŸ‘︎ 2
πŸ“°︎ r/intel
πŸ‘€︎ u/XeroShinobi
πŸ“…︎ Jul 09
🚨︎ report
There is a CPU-bound problem with Tarkov since the wipe...

... there is no denying it.

Stop suggesting people upgrade their CPUs when they state that the game was running perfectly before the last update. I myself have been playing just fine on my i5-7600k since late 2017.

Yes, that CPU is indeed outdated.

Yes, I would get better performances if I bought an i13 17999KXW.

But that didn't keep me from playing at perfectly decent perfs (50-80 fps most of the time) for close to 5 years.

HOWEVER, the last patch completely MURDERED Tarkov's CPU usage. Before the game used around 60-70% of the CPU ressources, with the occasional spike up. Now it is perma-capped at 100%, killing all responsiveness from the rest of the softwares : music freezes, Discord mates stop hearing me, .... Hell, even ingame inputs get frozen sometime (i.e. I let go off the W key but the character keeps running for 1-2 secs). Those things NEVER happened before, and the strangest part is that the FPS are perfectly fine still, I'd even say better than before.

I know I am not the only one.

Last patch brought with it an issue, and I hope the devs are working on a fix. I am not asking for troubleshooting help, I tried everything. It would be great to get an acknowledgement of the issue from the devs, though.

EDIT : someone pointed out that I might be due for repasting my CPU/GPU. They were right, I was even long overdue. However, this did not change anything except better temps. Myu CPU is still capped at 100% all the time.

πŸ‘︎ 134
πŸ“°︎ r/EscapefromTarkov
πŸ‘€︎ u/Trionlol
πŸ“…︎ Jul 12
🚨︎ report
RG552 Overclock Exceeds RP2+ Stock CPU Performance (multithreaded)
πŸ‘︎ 23
πŸ“°︎ r/SBCGaming
πŸ‘€︎ u/zackplanet42
πŸ“…︎ Mar 03
🚨︎ report
C++ Multithreading with Bounded Buffer

Hi, I (20M-Junior CS) need a mentor on a pretty advanced but not too long of an assignment I have. A lot of people are struggling and I really want to figure out and learn how to combine pipes, multi-threads, and bounded buffer to go together in this consumer-producer assignment. Please dm me if you are able to help in any way, thanks :)

πŸ‘︎ 3
πŸ‘€︎ u/batuwar09
πŸ“…︎ Mar 11
🚨︎ report
I never knew just how CPU bound this game was...

I always knew EFT as a game was CPU bound.. But I never knew just how.. I run the game at 1440p normally but had to RMA my card recently. The card I am stuck with is a GTX 680.. a 2GB card from 10 years ago that does not even get driver updates (outside of security patches). I am able to get 70-80 FPS on interchange and 110 on factory at 1080p on this card... I have a 6700k clocked at 4.5ghz. I did not even consider the possibility of running this game on this card considering valorant crashed every 60 seconds of playing. Of course my details are set to arse mode and I may have enabled downsampling. Crazy stuff and I am so happy that I wont be without the game.

πŸ‘︎ 54
πŸ“°︎ r/EscapefromTarkov
πŸ‘€︎ u/Taylor_Swifty13
πŸ“…︎ Jun 02
🚨︎ report
12400 Low CPU-Z Multithread score

Hi! Just installed new i5 12400 on Gigabyte B660M mobo. Fresh Windows 10 install. CPU-Z single thread score is 665 which is around what other reports suggest. Multithreaded score is only 2412 while HWMonitor shows 100% load on all threads but just around 43W consumption. Is there anything I've forgot to do? CPU-Z https://valid.x86.fr/x1lq6w HWonitor during stress test https://imgur.com/a/UXhTRZz Thanks!

πŸ‘︎ 2
πŸ“°︎ r/intel
πŸ‘€︎ u/Szturmix
πŸ“…︎ Feb 05
🚨︎ report
How do I make LEGO JW multithread my CPU?? Please its so laggy.

I'm running on an i7 8th gen.

πŸ‘︎ 2
πŸ“°︎ r/legogaming
πŸ‘€︎ u/AidanJoab
πŸ“…︎ Feb 09
🚨︎ report
BENCHMARK: +47% CPU performance and +14% GPU performance - 3.16 LIVE / 3.17 LIVE - good increase of average FPS overall and a bit more smoothness in CPU bound scenarios
πŸ‘︎ 316
πŸ“°︎ r/starcitizen
πŸ‘€︎ u/elecobama
πŸ“…︎ Apr 30
🚨︎ report
Voronoi Diagrams using CPU MultiThreading in Unity v.redd.it/6xdnynwjdyr71
πŸ‘︎ 111
πŸ‘€︎ u/Mr_developerYT
πŸ“…︎ Oct 07 2021
🚨︎ report
Is the slowdown when too much stuff that is on the screen CPU-bound? Would a different game engine help with it or is there anything we can do on our end to make it faster?

So near the endgame, you start getting Zerg rushed and make builds that spam the screen up with lots of stuff. This is when the game slows to a crawl.

Is this slowdown CPU or GPU bound? Would throwing more horsepower at it (higher end CPU/GPU) or reducing visual effects help this? Is this the game engine reaching its limits? Would another game engine that's designed to handle this much stuff on the screen help at all?

The slowdown can make things easier but it also kinda makes the endgame scenarios less intense.

πŸ‘︎ 2
πŸ“°︎ r/holocure
πŸ‘€︎ u/White_Phoenix
πŸ“…︎ Jul 18
🚨︎ report
This is my 12700KF/3080(3600c14) vs 12900K/6900XT(4000c15) both gear1, situation is cpu bound. Why is the result with amd gpu getting 1200fps highs where as i get only 1020s despite averaging higher? Isn't the gpu supposed to be irrelevant in a cpu bound scenario? reddit.com/gallery/vbj4pb
πŸ‘︎ 10
πŸ“°︎ r/overclocking
πŸ‘€︎ u/Glum-Shape-6516
πŸ“…︎ Jun 13
🚨︎ report
Has anyone benchmarked realtime kernels for CPU-bound games?

Games are very latency-sensitive; any increase has significant effects on the frame rate.
I've experienced this myself when trying to run compile jobs in the background while gaming. Even when they're at the lowest scheduling priority (SCHED_IDLE) that can allocate >99% of the CPU resources to other tasks, they still cause my game to lose ~30% of it's average frame rate (not to speak of stability): https://unix.stackexchange.com/questions/684152/how-can-i-make-my-games-fps-be-virtually-unaffected-by-a-low-priority-backgroun
This is likely due to buffer bloat; larger queues -> higher latencies.

RT-kernels are supposed to offer more consistent latency at the cost of throughput which should be a desirable attribute when gaming. 160fps is nice, high throughput but I'd rather have a more consistent 140fps.
Could they help this case or perhaps even generally be useful?

Has anybody done benchmarks on this? The newest I could find is a Phoronix benchmark from 2012 testing Ubuntu's Low-latency kernel which isn't very applicable today I'd say.

How do you even use a RT kernel? Would I have to give my game a specific priority?

πŸ‘︎ 39
πŸ“°︎ r/linux_gaming
πŸ‘€︎ u/Atemu12
πŸ“…︎ May 16
🚨︎ report
For client-side Blazor (WASM), how do you handle long-running, CPU-bound tasks?

I'm building a little client-side Blazor app for the game Elden Ring. The work that it needs to do takes about 10 seconds and is locking up the UI, and also making the "This page is slowing down Firefox. To speed up your browser, stop this page." message pop up.

I've given BlazorWorker a try in order to get this running in a separate thread/in the background, but it didn't seem to help here. Do I have any options other than to convert this to an ASP.NET hosted app and do the heavy lifting on the server?

πŸ‘︎ 9
πŸ“°︎ r/Blazor
πŸ“…︎ May 28
🚨︎ report
Poorly optimized or am I CPU bound?

I'm coming back after a break and don't think I realized how bad frame drops are in high pop areas. My CPU typically tops out around 78% to 82% during chest runs while GPU is around 40% to 50%. I would think my bottleneck is CPU but I've never seen it at 90+%.


  • CPU: AMD Ryzen 2600 at 3.7ghz
  • RAM: 16GB at 3600mhz
  • GPU: RTX 2070 Super

Edit: Forgot to add, I have a mix of medium and low settings and am playing at 1440p.

πŸ‘︎ 19
πŸ“°︎ r/newworldgame
πŸ‘€︎ u/jenkins_009
πŸ“…︎ Apr 23
🚨︎ report
CPU was determined to stop the clock with no TOs left. Treating out of bounds like the damn goal line. v.redd.it/q8fk4hqe7g691
πŸ‘︎ 35
πŸ“°︎ r/NCAAFBseries
πŸ‘€︎ u/ratfacedirtbag
πŸ“…︎ Jun 18
🚨︎ report
CPU raytracer multithreading

I’ve built a toy ray tracer previously in java, which I’m porting to c++, I’m now trying to multi-thread. I’m can’t work out why I am not seeing the performance increase I see in my java implementation (In c++ using multiple threads decreases performance speed). Could this be due to the memory bandwidth accessing the pixel array? I've also heard about false sharing, but I'm unsure whether this could be a problem here, and how to combat it if so. Any tips, pointers, or subjects to read about would be appreciated!

Here is a representation of how I’m processing the image, which shows the same performance using threads. Using rand() as an example to avoid posting a ton of ray-tracing code.


int image_width = 900;
int image_height = 500;

void main() {
    // 4 CHANNELS, R G B A
    unsigned char image_data[4 * image_width * image_height];

    while (true) {
        std::vector<std::thread> threads;
        int num_of_threads = 8;

        //Each thread handles a strip of pixels, image height / num of threads x             
        //full image width
        for (int i = 0; i < num_of_threads; i++) {
            int start_x = (image_width / num_of_threads) * i;
            int end_x = start_x + (image_width / num_of_threads);
            threads.emplace_back(std::thread(renderImage, image_data, start_x,
                                            end_x, 0, image_height));

        for (auto& thread : threads) {

        //Load image into texture to be displayed.
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image_width, image_height, 0,                        
                    GL_RGBA, GL_UNSIGNED_BYTE, image_data);

void renderImage(int start_x, int end_x, int start_y, int end_y, unsigned char*                 
                pixels) {

    for (int j = start_y; j < end_y; j++) {
        for (int i = start_x; i < end_x; i++) {
            int index = 4 * (j * image_width + i);

            //Set random values to each channel.
            pixels[index] = (int)(((double)rand() / (RAND_MAX)) * 255);
            pixels[index + 1] = (int)(((double)rand() / (RAND_MAX)) * 255);
            pixels[index + 2] = (int)(((double)rand() / (RAND_MAX)) * 255);
            pixels[index + 3] = 255;
... keep reading on reddit ➑

πŸ‘︎ 19
πŸ‘€︎ u/joshcvdd
πŸ“…︎ Aug 05 2021
🚨︎ report
Question ..If i offload tasks to a new cpu thread will we lose boost frequency ? due to how the multithread is handled
πŸ‘︎ 6
πŸ“°︎ r/unrealengine
πŸ‘€︎ u/azh210
πŸ“…︎ Nov 30 2021
🚨︎ report
So, when I mod the game, does it become more GPU bound or CPU bound?

Obviously, the game becomes harder to run with mods. But, I've got some cash kicking around and with these price drops, I've been considering swapping out my RTX 2060 for either a 3060 or 3060TI. My CPU is a Ryzen 3700x, so I don't feel like the game is TOO much for that, even with mods. (The game runs fine without mods, consistently 90 FPS. With mods, there is a noticeable lag, I feel like the FPS range is somewhere between 50-60.)

πŸ‘︎ 5
πŸ“°︎ r/H3VR
πŸ‘€︎ u/ThePilate
πŸ“…︎ May 28
🚨︎ report
Up to 15% performance gains in CPU-bound specs with global invalidation playvalorant.com/en-us/ne…
πŸ‘︎ 243
πŸ‘€︎ u/freakout40404
πŸ“…︎ Mar 08
🚨︎ report
I have a 48GB DDR4 setup that I want to upgrade the CPU. Primarily play CPU-bound games. What options should I consider?

Why am I using 48GB RAM running at 2933 MHz (2x8GB 3200 Mhz and 2x16 3600 MHz kits) with my Ryzen 1600? Modded Cities Skylines uses over 30GB memory. I would have considered an Optane drive for page file usage if they were more affordable.

While I do have a RX 570 4GB and a 1080p 60Hz monitor, I intend on upgrading the GPU when prices are more reasonable and getting a second monitor with a new GPU.

The problem is that Cities Skylines remains an absolute CPU hog, and I recently installed mods that extended the game engine's limits for an even larger city, so I expect memory and CPU usage will go up with that.

The other games that I play are Civilization 6 (also CPU bound, especially on huge maps full of AI civs and city states, and I think the mods are likely making it even more of a CPU hog with all of the extra features they added) and occasionally Total War Shogun 2 (single core and FPS falls below 30 in large battles on the Ryzen 1600).

The options I am looking at are:

  • i5 12400, preferably with a DDR4 motherboard bundle as I would need a new mobo.

  • i5 12600K with a DDR4 Z690 motherboard bundle deal that I've been looking at for $397: https://www.reddit.com/r/buildapcsales/comments/u9971w/cpuboard_i5_12600k_z690_gaming_x_ddr4_397_makes/

  • Ryzen 5600

  • Ryzen 5700 (only if I know for certain if I'll be playing a game that scales to 6-7 cores so Windows 10's background services and other background applications don't impact the gaming)

  • Ryzen 5800X3D (if I get this, I would be riding the system until DDR6 had already launched...)

I don't plan on any major overclocking. If it's much cheaper for me to go with a non-K edition i5 and non-OCing motherboard, I'll strongly consider that as long as I can still do some RAM OCing as otherwise the motherboard might default to something like 2133/2400 MHz with the 48GB kit (which my B450 board will do on its own if I don't manually OC the RAM).

EDIT, it seems that non-K edition CPUs might have issues with RAM OCing, which makes me concerned as I absolutely do not want to be running my RAM at sub-2933 MHz:



πŸ‘︎ 8
πŸ“°︎ r/intel
πŸ‘€︎ u/COMPUTER1313
πŸ“…︎ Apr 23
🚨︎ report
Hear me out, I understand these CPUs are 10 years old but, this kind of performance? Really? Does anyone know what's going on? (Dual Xeon x5670s | 2.93GHz turbo to 3.33GHz | combined 12 cores 24 threads). for reference, the CPU-Z benchmark matched these up with the Ryzen 7 1700 in multithread prf. v.redd.it/j6c8v6vpw9g71
πŸ‘︎ 5
πŸ“°︎ r/BeamNG
πŸ‘€︎ u/MrPeanutPlays
πŸ“…︎ Aug 09 2021
🚨︎ report
When gaming at 1080p and being CPU bound, which upgrade would give more FPS, GPU or CPU

Hello all,

I'm just curious because my brother is getting a 1080p monitor to pair with his rtx 3060 ti and R5 5600x.

From what I see on this sub, gaming at 1080p leaves you CPU bound and I was wondering that surely upgrading a GPU would still allow you to push out more FPS since it's supposed to be a better GPU or would you only notice a significant difference by getting a better CPU, say an R7 5800x?

πŸ‘︎ 14
πŸ“°︎ r/buildapc
πŸ‘€︎ u/JjayaitchH_
πŸ“…︎ Apr 14
🚨︎ report
Has anyone figured out multithreading or multiple cores/cpus in one unit for the 8 bit cpu?

I'm getting the 8 bit cpu on the third (payday lol) and I'm really excited to build it! I'm going into Electrical Engineering + Computer Science courses this fall and I can't wait to get some hands on experience with the kit. So my question is stated in the title. I would also like some additional resources so I can go ham crazy with this!

πŸ‘︎ 2
πŸ“°︎ r/beneater
πŸ‘€︎ u/FoxyCatDogThing
πŸ“…︎ Jul 29 2021
🚨︎ report
Should I upgrade to 5900x from 5600x? or wait for am5 cpu's? when I play vrchat or pavlov I find myself cpu bound so I was looking for more power in this area. I'm asking because the 5900x is on sale right now and I don't know much about the zen 4 cpu line up.
πŸ‘︎ 2
πŸ“°︎ r/Amd
πŸ‘€︎ u/supa_manJ1
πŸ“…︎ Apr 12
🚨︎ report
Nearly 3 Trillion simulations between my 2 machines. Also an update to my Multithreaded CPU simulator, now very easy to use. (Link in comments).
πŸ‘︎ 64
πŸ“°︎ r/DreamWasTaken2
πŸ‘€︎ u/77xak
πŸ“…︎ Jan 14 2021
🚨︎ report
Does the game become more CPU-bound or GPU-bound when it's modded?

Obviously, the game becomes harder to run with mods. But, I've got some cash kicking around and with these price drops, I've been considering swapping out my RTX 2060 for either a 3060 or 3060TI. My CPU is a Ryzen 3700x, so I don't feel like the game is TOO much for that, even with mods. (The game runs fine without mods, consistently 90 FPS. With mods, there is a noticeable lag, I feel like the FPS range is somewhere between 50-60.) my question is mainly, would upgrading my GPU actually improve my performance as much as I think it would?

πŸ‘︎ 4
πŸ“°︎ r/H3VRMods
πŸ‘€︎ u/ThePilate
πŸ“…︎ May 28
🚨︎ report

Please note that this site uses cookies to personalise content and adverts, to provide social media features, and to analyse web traffic. Click here for more information.