dlmalloc | C version of Doug Lea 's excellent malloc implementation
kandi X-RAY | dlmalloc Summary
kandi X-RAY | dlmalloc Summary
A C++ version of Doug Lea's excellent malloc() implementation. I have been having issues with the malloc() implementation on Windows, where the memory usage can grow unreasonably large with some patterns of successive reallocations. So I decided to investigate Doug Lea's malloc implementation. It is very easy to use, a single C file that you just compile and link along with your source code, and you are all set. Using Doug's malloc.c worked beautifully. For my use case, it was faster than Windows default malloc (I'm using Visual C++ 2015), and the memory usage was considerably reduced. I wanted to understand the code, as I would like to use its core logic to make a custom C++ allocator for my sparse hash table. However, I found the source code very difficult to follow. A lot of it is implemented with preprocessor macros, and is invisible to debuggers. Macros are of course necessary when coding in C for ultimate performance, but they sure obfuscate the code. Also, I'd like my C++ allocator to be header only, but shoving all these macro definitions into a header file would pollute the global name space, which is not acceptable. Therefore I decided to convert Doug's original malloc.c (v2.8.6) to C++, and this is what you find here. I have not modified what the code does, just how it is specified and organized (modulo any typo or bug I may have introduced of course). Interestingly, the C++ version is just as fast as the original C version! In my tests (Visual C++ 2015, Windows 10), the C++ version was even very slightly faster. While Linus may be opposed to C++, I still though that sharing this C++ implementation could be useful for people who, like me, would like to examine the inner workings of one of the best malloc implementation ever written.
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Trending Discussions on dlmalloc
QUESTION
My first Rust-produced WASM is producing the following error, I have no idea how to go about it debugging.
...ANSWER
Answered 2019-Apr-19 at 15:12Your problem is that you create a chunk of uninitialized memory and don't initialize it properly:
QUESTION
Here is a detailed description of the dlmalloc algorithm: http://g.oswego.edu/dl/html/malloc.html
A dlmalloc chunk is bookended by some metadata, which includes information about the amount of space in the chunk. Two contiguous free chunks might look like
...ANSWER
Answered 2017-Jun-04 at 18:30You can see the answer yourself by looking at the source. Begin with line 1876 to verify your diagram. The metadata is just two size_t
unsigned integers, accessed by aliasing a struct malloc_chunk
(line 1847). Field prev_size
is the size of the previous chunk, and size
is the size of this one. Both include the size of the struct malloc_chunk
itself. This will be 8 or 16 bytes on nearly all machines depending on whether the code is compiled for 32- or 64-bit addressing.
The "normal case" coalescing code starts at line 3766. You can see that the size
variable it's using to track coalescing is chunk size.
So - yeah - in the code blocks marked /* consolidate backward */
and /* consolidate forward */
, when he adds the size of the preceding and succeeding chunks, he's implicitly adding the size of the struct malloc_chunk
as you suspected.
This shows that your interpretation is correct. My expectation is that the textbook author just got sloppy about the difference between chunk size (which includes metadata) and the size of the memory block allocated to the user. Incidentally, malloc
takes care of this difference at line 3397.
Perhaps the bigger lesson here is that - when you're trying to learn anything - you should never skip an opportunity to go straight to the first-hand source and figure stuff out for yourself.
QUESTION
Crashing at sws_scale when converting an AVPicture
At first I was using sws_scale to actually scale the frames up but the cpu overhead was too high, so I decided to just convert the frames and adjust the QImage size instead. Before it was working and I was getting the video displaying when rendered, but now it crashes at sws_scale.
This is written in Qt for Android and using FFMpeg 3.1.4.
Also, is there another way around not using the deprecated functions?
Does anybody know why I am getting the crash at sws_scale?
The class for the VideoFrameCopy
...ANSWER
Answered 2017-Mar-01 at 19:17Regarding the crash: it would be helpful to understand whether access violation was related to reading input picture or writing output picture. Anyway, so far I can see only one issue with the code: you cannot use av_image_fill_linesizes
when using QImage as a target. Linesizes must match actual image layout (just like data pointers must match actual image position in memory) so use something like this:
QUESTION
I am trying to compile the mbed client example on a windows machine for the K64F board. I have installed all the required software as described in the guide https://github.com/ARMmbed/mbed-client-quickstart.
The commands I have run are the following commands:
...ANSWER
Answered 2017-Feb-20 at 12:18That's the old example code based on mbed OS 3. Use the example for mbed OS 5 instead.
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