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记一次MongoDB性能问题 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...验证这种可能，我搜索了一下MongoDB日志：
shell> grep FileAllocator /path/to/log
[FileAllocator] allocating new datafile ... filling with zeroes...
[FileAllocator] done allocating datafile ... took ... secs
我使用的文件系统是ext4（xfs也不错 ），创建数据文件...
Can a local variable's memory be accessed outside its scope?
...mpiler generates calls into a "heap manager" that knows how to dynamically allocate storage when it is needed and reclaim it when it is no longer needed.
The second method is to have a “short-lived” storage area where the lifetime of each byte is well known. Here, the lifetimes follow a “nest...
How can I get a count of the total number of digits in a number?
...
@Krythic string allocation is the new craze in .NET world.
– nawfal
Dec 9 '16 at 7:16
1
...
What is the difference between \r and \n?
...ine.
ASCII encodes these actions as two distinct control characters:
\x0D (CR) moves the print head back to the beginning of the line. (Unicode encodes this as U+000D CARRIAGE RETURN.)
\x0A (LF) moves the print head down to the next line. (Unicode encodes this as U+000A LINE FEED.)
In the da...
Why is it bad practice to call System.gc()?
...ly not necessarily true - the Java heap itself grows independently of Java allocations.
As in, the JVM will hold memory (many tens of megabytes) and grow the heap as necessary. It doesn't necessarily return that memory to the system even when you free Java objects; it is perfectly free to hold o...
Change old commit message on Git
...d line with the following message:
$ git rebase -i HEAD~3
Stopped at 7482e0d... updated the gemspec to hopefully work better
You can amend the commit now, with
It does not mean:
type again git rebase -i HEAD~3
Try to not typing git rebase -i HEAD~3 when exiting the editor, and it should work f...
How do I find where an exception was thrown in C++?
...bt]: (8) ./test(__libc_start_main+0x95) [0x42017589]
[bt]: (9) ./test(__eh_alloc+0x3d) [0x8048b21]
signal 6 (Aborted), address is 0x1239 from 0x42029331
crit_err_hdlr backtrace returned 13 frames
[bt]: (1) ./test(kill+0x11) [0x42029331]
[bt]: (2) ./test(abort+0x16e) [0x4202a8c2]
[bt]: (3) ./test [...
push_back vs emplace_back
...ving does not make s invalid, the move will only steal the internal memory allocation already done in s and leave it in a defaulted state (no sting allocated) which when destructed will be fine as if you had just typed std::string str;
– David
Nov 30 '10 at 0:5...
How to add spacing between UITableViewCell
...Path
{
if (cell.IsMonth)
{
UIImageView *av = [[UIImageView alloc] initWithFrame:CGRectMake(20, 20, 20, 20)];
av.backgroundColor = [UIColor clearColor];
av.opaque = NO;
av.image = [UIImage imageNamed:@"month-bar-bkgd.png"];
UILabel *monthTextLabel = [[U...
How to get the source directory of a Bash script from within the script itself?
...-sa/3.0/
18eedfe1c99df68dc94d4a94712a71aaa8e1e9e36cacf421b9463dd2bbaa02906d0d6656
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