On Tue, 11 Nov 2014, Sergei Gorelkin wrote:
11.11.2014 12:35, Jonas Maebe пишет:
On 11/11/14 10:28, Adriaan van Os wrote:
Jonas Maebe wrote:
On 10/11/14 18:47, Karoly Balogh (Charlie/SGR) wrote:
It's remove_freed_fixed_chunks(). Can someone explain to me under what
condition this code is triggered very often and/or could take long to
execute (there's a loop in there)?
This was reported earlier too, but I couldn't reproduce it:
http://bugs.freepascal.org/view.php?id=18079 (especially comment 47405
by Sergei).
I suggest to use cmem and compare the results.
I will also note that malloc uses mremap
None of that would explain the differences experienced in the referred
bug report, because we don't use mremap-like functionality on any
platform at this time. The issue there appears to be a corner case that
makes the heap manager reformat/free/reallocate its internal heap blocks
all the time on some systems, while on other systems it won't do that
even though it's presented with exactly the same memory
allocation/reallocation pattern.
This behavior apparently depends on all memory serviced by memory manager,
including blocks
allocated (and maybe also freed) during RTL initialization. That's why it
differs between targets,
and that's why the issue 18079 was no longer reproducible after time. Most
probably some (unrelated)
change was made to RTL initialization code, which also changes the pattern in
user code that is
required to reproduce issue.
I have some code that - most likely - reproduces this.
The exact same code sometimes takes less than a second to run, sometimes it
takes around 20 seconds:
It simply randomly allocates and deallocates blocks of memory of up to 1024
bytes.
When I straced the code, I could see it was running mmap and mmunmap all the
time.
I used this code to 'simulate' a fragmented heap before starting a timing of my
"business code".
Michael.
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