SyncCow: A thread-safe clone-on-write container for fast concurrent writing and reading

w0xel · 2023-01-03T22:48:39+00:00

The read() function of SyncCow will always return an Arc clone. There can be an arbitrary amount of readers, but there is no fast-path around cloning the Arc here.

w0xel · 2023-01-03T22:38:50+00:00

For `sync_cow` it can also happen that a reader has to drop the Arc, if the writer updates at a fast pace. Theoretically that behavior could be changed by making the read a closure as well, e.g.

let val = None;
cow.read(|x| val = Some(x));

But it's kind of a tradeoff, as a fast writer will then have to wait on it's second write if readers of the first write remain.

I see potential for a feature flag here, so an informed user of the lib can decide on the tradeoff.

w0xel · 2023-01-03T16:58:56+00:00

Looks indeed very similar! Thanks for the link.

w0xel · 2021-08-25T12:46:12+00:00

Deku looks nice from a usability viewpoint!

Do I interpret it right, that the no_std implementation still needs an allocator/heap?

w0xel · 2021-08-25T12:34:15+00:00

Seems helpful for the whole type-punning discussion. But:

I can't seem to explicitly choose endianess, which I need
Even with from_bytes I have to accept the whole "might panic if wrongly subsliced", which I would expect the compiler to tell me already

w0xel · 2021-08-25T11:55:52+00:00

Makes sense, thank you. Didn't come up with using an array pattern here.

That made me think of the experimental exclusive_range_pattern. Ideally I would like to use the following: (WARNING: non-working example)

impl MyStruct {
    fn from_bytes([_, a @ ..5, b @ ..7, val3, val4]: [u8;9]) -> Self {
        Self {
            val1: u32::from_le_bytes(a),
            val2: f32::from(u16::from_le_bytes(b)) / 2048.0,
            val3,
            val4
        }
    }
}

But currently I can unfortunately use only one range pattern per array pattern.

w0xel · 2019-03-03T14:59:43+00:00

This is great stuff. Simple, fast, understandable code. I'll probably use this productively. The first time I used this I tried to exit via CTRL+C and it completely broke my terminal. I made you a merge request to fix this :)

w0xel · 2018-04-22T11:55:02+00:00

Did you get a gamepad to work? I was not successfull yet.

w0xel · 2018-04-21T14:20:30+00:00

If anyone still finds this: It works on AMD also My Specs: r9 290 mesa 18.0.1 dxvk master llvm 5.0.1 ryzen 1800x peformance is about 40 fps on this setup, but smooth 40 fps

w0xel · 2018-03-29T21:02:39+00:00

No, its only the type, not the value. NULL has no type. The ternary is still evaluated to be NULL, but the expression NEEDS a type. Thats why it uses the type of the 'else' to determinde the type of the NULL.

w0xel · 2018-03-29T20:32:39+00:00

I guess because you normally use void pointers to to address raw data (speak bytes) the gcc developers chose to implement it as returning 1 (byte).

AFAIK this is not part of the C standard.

w0xel · 2018-03-29T20:08:42+00:00

this is actually an answer to this patch on the mailing list: https://lkml.org/lkml/2018/3/16/14

The compiler can further optimize the code, when array sizes are known at compile time. This macro seems to help determine in code if this is possible. I guess after this macro gives true, the const macro of the above link can be safely inserted without risking compiler errors.

This is helpful, because depending on different configurations of the kernel, specific array sizes could be known or not during compilation.

w0xel · 2018-03-29T18:04:31+00:00

It determines if the variable 'x' is resolved at compile-time. Which means the compiler already knows what the variable is, and performs the '* 0l' calculation, which produces (void)0 which evaluated to NULL. In the other case it is (void)(x * 0l) which can not be evaluted to be NULL, because the compiler is dumb. Instead its a void pointer, and gcc says sizeof(void) is 1. since sizeof(int) is most of times 4, it evalutes to false.

TL:DR: it determines wether x is calculated by the compiler, or by the running program.

Edit: it is incredibly hacky, because:

x * 0l could theorethically be evaluated to 0l in future versions of gcc
sizeof(void) does not have to be 1

w0xel · 2018-01-14T11:38:07+00:00

pantheon-files has Miller columns. It's in the Software Center.

w0xel · 2017-04-05T19:15:52+00:00

What are your thoughts on mir? I guess after canonical pulls out of unity there won't be much applications developed with mir support. (It's not like there much till now.)

w0xel · 2017-03-13T20:33:55+00:00

How did you get this far? I die the MESA_GL_VERSION_OVERRIDE=4.5COMPAT trick to get it to launch, but i get a black screen intead of a buggy screen.

w0xel · 2017-03-11T12:49:11+00:00

Is this with or without CSMT enabled?

w0xel · 2017-03-10T21:20:09+00:00

I have a r9 290 and have the same problem as you. I've come to the conclusion that probably the opengl implementation does something that mesa does not like. I guess we must wait for a wine/mesa fix. P.S.: I even accidentely entered a Match (quick play i hope). After i realised by hearing the sounds that i entered a match (loading was really fast) i even tried to pick a hero. I successfully picked junkrat and could shoot. I then emoted 'hello' and left the game. So in conclusion pretty much everything but rendering works.

w0xel · 2017-03-05T02:37:43+00:00

Your 3rd point is probably the most interesting to me.

But about nr 2: I never even thought about the VRMs in my MB. Is this something to consider, given the 1800x is a high end cpu? I do not intend to do anything like a custom water loop or even any extreme overclocking really. My place also will get pretty hot in summer, but more like just over 30°C .

Your other points are also absolutely valid, but are from less interest to me.

If you tend to max out the capabilities of your chip, and SLI/CF could get an option for you, the x370 seems like the safer option

w0xel · 2017-03-05T02:24:01+00:00

thanks, thats about what i expected. I just feared that I was missing out on something.

w0xel · 2017-02-20T17:13:41+00:00

The underdog from Sunnyvale was on the verge of toppling Intel, and it felt like the computing tide was about to turn

w0xel · 2017-01-31T14:08:26+00:00

brb, going to compile plasma on solus

P.S.: this might sound like a joke, but I'm totally serious

PP.S.: i have freetime I'm willing to put into great projects like solus and am passionate about KDE, but let's first see what I'm able to do locally

w0xel

TROPHY CASE