I am unable to identify the root cause for the below leak shown in the image. It is showing as Malloc 16 Bytes, how to resolve this memory leak.Any help could be appreciated
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good people of the Internet!
A past couple of days I've been reading about how CPU access memory and how it could be slower then desired if the accessed object is spread over different chunks that CPU accesses.
In a very generalized and abstract words, if I, say, have an address space from 0x0 to 0xF with a cell of one byte, and CPU reads memory in chunks of 4 bytes (that is, has a quad byte memory access granularity), then, if I need to read an object of 4 bytes size residing in cells 0x0 - 0x3, CPU would do it in one operation, while if the same object occupies cells 0x1 - 0x4, then CPU needs to perform two read operations (read memory in 0x0 - 0x3 first, then in 0x4 - 0x7), shift bytes and combine two parts (or break, if it cannot do unaligned access). This happens, once again, because CPU can read memory in 4 bytes chunks (in our abstract case). Let's also assume, that CPU make these reads inside one cache line and there is no need to change the contents of cache between reads.
So, in this case, the beginning of each chunk CPU can read is residing in a memory cell that has an address which is multiple of 4 (right?). Ok, i don't have any questions about why CPU reads in chunks, but why exactly the beginning of each chunk is aligned in such a way? If referring to an example in a previous paragraph, why exactly CPU cannot read a chunk of 4 bytes starting from 0x1?
As I may understand, CPU is pretty much aware that 0x1 exists. So is all the fuzz happening because memory controller cannot access chunk of memory starting from 0x1? Or is it because a couple of LSBs in a processor word are reserved on some architectures? Or the fact that they are reserved is the consequence of an aligned access, an not its cause (it seems like it's a second question already, but I would leave it as at the time I write this question I have a feeling that they are related)?
There are a bunch of answers here touching this topic (like this and this) and articles online (like this and this), but in all the resources there are good explanations on the phenomena itself and its consequences, but no explanation on why exactly CPU cannot read a chunk of memory starting "in between" byte boundaries (or I couldn't see it maybe).
Consider a simple CPU. It has 32 RAM chips. Each chip supplies one bit of memory. The CPU produces one address, passes it to the 32 RAM chips, and 32 bits come back. The first RAM chip holds bit 0 of bytes 0, 4, 8, 12, 16 etc. The second RAM chip holds bit 1 of bytes 0, 4, 8, 12, 16 etc. The ninth RAM chip holds bit 0 of bytes 1, 5, 9, 13, 17 etc.
So you see that the 32 RAM chips between them can produce bits 0 to 7 of bytes 0 to 3, or bytes 4 to 7, or bytes 8 to 11 etc. They are incapable of producing bytes 1 to 4.
Reading here it says malloc can't allocate less than 32 bytes. I have also seen somewhere saying 16 bytes is the minimum.
This diagram shows generally what malloc block looks like, but is not detailed enough.
The first link suggests there is an 8-byte minimum required to store the size of the block. Piecing these things together, my guess is:
16 bytes for the size (this, but that would limit block size to 65,535 bytes)
16 bytes for the pointer to the next free block (but that would also limit the number of blocks to 65,535 ~ 4 GB, which I guess makes sense).
That would mean the block structure would be:
[size, pointer, userdata....]
[16b, 16b, 65,535b max]
This would mean malloc can't allocate less than 16 + 16 + 16 = 48 bytes.
Wondering if this is accurate or if there is more to it.
Fatal error: Allowed memory size of 792723456 bytes exhausted (tried to allocate 1764582776 bytes) in C:\xampp\htdocs\magento\vendor\magento\framework\ObjectManager\Relations\Runtime.php on line 38
Fatal error: Allowed memory size of 792723456 bytes exhausted (tried to allocate 1764582776 bytes) in C:\xampp\htdocs\magento\vendor\magento\framework\ObjectManager\Relations\Runtime.php on line 38
Please check your php.ini setting and memory limit. Kindly increase execution time and memory limit.
Also please add memory limit in your index.php file on the root of magento
ini_set('memory_limit','-1');
I have several crash reports from an iOS app that stem from a SIGABRT in a free() call.
The call stack is consistent:
0 libsystem_kernel.dylib 0x3863c1f0 __pthread_kill + 8
1 libsystem_c.dylib 0x385ecfdd abort + 77
2 libsystem_malloc.dylib 0x38664d67 free + 383
I'm trying to get more diagnostics, but in the meantime, did anyone encounter the same? What kind of a wrong argument would crash a free() call? I can see several options:
a null pointer (actually legit)
a data area pointer (i. e. a string literal)
a stack pointer
a garbage pointer (i. e. an uninitialized one)
a heap pointer that was already freed
Any ideas please? Those are pretty rare, the last one was in Sep
'14. But I've got over 10 total, there is probably a bug there.
If I read the stack dump correctly, the code triggered an assertion in free and called abort. Look at the source code for the libsystem_malloc on http://opensource.apple.com and try and figure which assertion failed.
You have a stray pointer, guessing where it is hiding from a single non reproducible crash is next to impossible. Running your application in the emulator with valgrind (if that's possible) may help you track memory misuse.
It the stack dump is longer that 3 lines, you should have an indication of which call to free caused the problem. It may help you track the bug, but it may also be a late side-effect of some earlier pointer misuse.
I am using PHPbb , everything works fine,
But i am getting the following error in a single page inside admin.
Allowed memory size of 16777216 bytes exhausted (tried to allocate 78 bytes) in home/mytestsite/public_html/includes/template.php on line 458
How to fix this error?
As you can imagine, this error message occurs when PHP tries to use more memory than is avialable. I'm assuming that changing code is not an option but you CAN increase the amount of memory available to PHP.
To change the memory limit for one specific script, include a line such as this at the top of the script:
ini_set("memory_limit","20M");
The 12M (for example) sets the limit to 20 Megs. If this does not work, keep increasing the memory limit until your script fits or your server squeals for mercy.
You can also make this a permanent change for all PHP scripts running on the server by adding a line such as this to the server’s php.ini file:
memory_limit = 20M
Hope this helps