大量生产临时变量，可以使用AutoReleasePool 降低性能的峰值
NSOperation*operation = [NSOperationnew];
dispatch_async(self.ioQueue, ^{
if(operation.isCancelled) {
return;
}
@autoreleasepool{
UIImage*diskImage = [selfdiskImageForKey:key];
if(diskImage &&self.shouldCacheImagesInMemory) {
NSUIntegercost =SDCacheCostForImage(diskImage);
[self.memCachesetObject:diskImageforKey:keycost:cost];
}
dispatch_async(dispatch_get_main_queue(), ^{
doneBlock(diskImage,SDImageCacheTypeDisk);
});
}
});
