iphone - iOS objc::DenseMap性能

Question

我正在研究iOS 5项目，并且遇到了严重的性能问题，使我的应用程序始终降低到<10fps。时间分析工具已识别出对objc::DenseMap的调用，这似乎与Objective-C运行时中的保留/释放/自动释放系统有关。该调用占用了大量的处理时间，我想知道是否有人可以解决该惩罚和/或避免此问题的方法。我怀疑这与NSMutableArrays，NSMutableSets和我用来管理每帧对象的其他可变集合有关。任何跟踪或解决此问题的建议或见解将不胜感激。以下是跟踪中看起来很重要或相关的所有内容:

Running Time    Self        Symbol Name
1426.0ms    7.2%    1426.0      objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*>, objc::DenseMapInfo<unsigned long> >::LookupBucketFor(objc_object* const&, std::pair<objc_object*, unsigned long>*&) const
817.0ms    4.1% 0.0      objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*>, objc::DenseMapInfo<unsigned long> >::FindAndConstruct(objc_object* const&)
817.0ms    4.1% 0.0       _objc_rootRetain
817.0ms    4.1% 0.0        -[NSObject retain]
773.0ms    3.9% 0.0         objc_retain
28.0ms    0.1%  0.0         -[NSMutableArray removeObject:]
11.0ms    0.0%  0.0         CFRetain
580.0ms    2.9% 0.0      objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*>, objc::DenseMapInfo<unsigned long> >::find(objc_object* const&)
580.0ms    2.9% 0.0       _objc_rootReleaseWasZero
580.0ms    2.9% 0.0        _objc_rootRelease
562.0ms    2.8% 0.0         objc_release
1.0ms    0.0%   0.0         CFRelease
19.0ms    0.0%  0.0      objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*>, objc::DenseMapInfo<unsigned long> >::grow(unsigned int)
19.0ms    0.0%  0.0       objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*>, objc::DenseMapInfo<unsigned long> >::InsertIntoBucket(objc_object* const&, unsigned long const&, std::pair<objc_object*, unsigned long>*)
19.0ms    0.0%  0.0        objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*>, objc::DenseMapInfo<unsigned long> >::FindAndConstruct(objc_object* const&)
19.0ms    0.0%  0.0         _objc_rootRetain
19.0ms    0.0%  0.0          -[NSObject retain]
15.0ms    0.0%  0.0           objc_retain
4.0ms    0.0%   0.0           -[NSMutableArray removeObject:]
5.0ms    0.0%   0.0      _objc_rootRetain
5.0ms    0.0%   0.0       -[NSObject retain]
4.0ms    0.0%   0.0        objc_retain
3.0ms    0.0%   0.0         objc_retainAutoreleasedReturnValue
1.0ms    0.0%   0.0        -[NSMutableArray removeObject:]
3.0ms    0.0%   0.0      _objc_rootReleaseWasZero
3.0ms    0.0%   0.0       _objc_rootRelease
3.0ms    0.0%   0.0        objc_release
2.0ms    0.0%   0.0      objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*>, objc::DenseMapInfo<unsigned long> >::erase(objc_object* const&)
2.0ms    0.0%   0.0       objc_clear_deallocating
2.0ms    0.0%   0.0        objc_destructInstance
2.0ms    0.0%   0.0         CFRelease

Answer 1

从性能分析中筛选出系统库，然后查看指示内容。您正在查看堆栈的错误端。

通常，您的代码是一个相对较薄的单板，以创建特定应用程序所需的任何方式将系统框架粘合在一起。像这样的性能问题通常表明您的应用实现在算法上不理想；也许您经常重新整理资料，也许在使用缓存时清空/填充收藏夹，等等。