Revert back the NSOperationQueue, seems has better performance on this cases (may dispatch multiple block but not important, one finished is OK)

SDWebImage/Core/SDAnimatedImagePlayer.m

@@ -90,6 +90,7 @@
     if (!_fetchQueue) {
         _fetchQueue = [[NSOperationQueue alloc] init];
         _fetchQueue.maxConcurrentOperationCount = 1;
+        _fetchQueue.name = @"com.hackemist.SDAnimatedImagePlayer.fetchQueue";
     }
     return _fetchQueue;
 }

SDWebImage/Core/SDImageCache.m

@@ -118,7 +118,7 @@ static NSString * _defaultDiskCacheDirectory;
         
         // Create IO queue
         dispatch_queue_attr_t ioQueueAttributes = _config.ioQueueAttributes;
-        _ioQueue = dispatch_queue_create("com.hackemist.SDImageCache", ioQueueAttributes);
+        _ioQueue = dispatch_queue_create("com.hackemist.SDImageCache.ioQueue", ioQueueAttributes);
         NSAssert(_ioQueue, @"The IO queue should not be nil. Your configured `ioQueueAttributes` may be wrong");
         
         // Init the memory cache

SDWebImage/Core/SDWebImageDownloader.m

@@ -116,7 +116,7 @@ void SDWebImageDownloaderOperationSetCompleted(id<SDWebImageDownloaderOperation>
         [_config addObserver:self forKeyPath:NSStringFromSelector(@selector(maxConcurrentDownloads)) options:0 context:SDWebImageDownloaderContext];
         _downloadQueue = [NSOperationQueue new];
         _downloadQueue.maxConcurrentOperationCount = _config.maxConcurrentDownloads;
-        _downloadQueue.name = @"com.hackemist.SDWebImageDownloader";
+        _downloadQueue.name = @"com.hackemist.SDWebImageDownloader.downloadQueue";
         _URLOperations = [NSMutableDictionary new];
         NSMutableDictionary<NSString *, NSString *> *headerDictionary = [NSMutableDictionary dictionary];
         NSString *userAgent = nil;

SDWebImage/Core/SDWebImageDownloaderOperation.m

@@ -75,7 +75,7 @@ BOOL SDWebImageDownloaderOperationGetCompleted(id<SDWebImageDownloaderOperation>
 
 @property (strong, nonatomic, readwrite, nullable) NSURLSessionTaskMetrics *metrics API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0));
 
-@property (strong, nonatomic, nonnull) dispatch_queue_t coderQueue; // the serial operation queue to do image decoding
+@property (strong, nonatomic, nonnull) NSOperationQueue *coderQueue; // the serial operation queue to do image decoding
 
 @property (strong, nonatomic, nonnull) NSMapTable<SDImageCoderOptions *, UIImage *> *imageMap; // each variant of image is weak-referenced to avoid too many re-decode during downloading
 #if SD_UIKIT
@@ -112,7 +112,9 @@ BOOL SDWebImageDownloaderOperationGetCompleted(id<SDWebImageDownloaderOperation>
         _finished = NO;
         _expectedSize = 0;
         _unownedSession = session;
-        _coderQueue = dispatch_queue_create("com.hackemist.SDWebImageDownloaderOperation", DISPATCH_QUEUE_SERIAL);
+        _coderQueue = [[NSOperationQueue alloc] init];
+        _coderQueue.maxConcurrentOperationCount = 1;
+        _coderQueue.name = @"com.hackemist.SDWebImageDownloaderOperation.coderQueue";
         _imageMap = [[NSMapTable alloc] initWithKeyOptions:NSPointerFunctionsStrongMemory valueOptions:NSPointerFunctionsWeakMemory capacity:1];
 #if SD_UIKIT
         _backgroundTaskId = UIBackgroundTaskInvalid;
@@ -466,23 +468,26 @@ didReceiveResponse:(NSURLResponse *)response
         NSData *imageData = self.imageData;
         
         // keep maximum one progressive decode process during download
-        @weakify(self);
-        dispatch_async(self.coderQueue, ^{
-            @strongify(self);
-            if (!self) {
-                return;
-            }
-            // When cancelled or transfer finished (`didCompleteWithError`), cancel the progress callback, only completed block is called and enough
-            if (self.isCancelled || SDWebImageDownloaderOperationGetCompleted(self)) {
-                return;
-            }
-            UIImage *image = SDImageLoaderDecodeProgressiveImageData(imageData, self.request.URL, NO, self, [[self class] imageOptionsFromDownloaderOptions:self.options], self.context);
-            if (image) {
-                // We do not keep the progressive decoding image even when `finished`=YES. Because they are for view rendering but not take full function from downloader options. And some coders implementation may not keep consistent between progressive decoding and normal decoding.
-                
-                [self callCompletionBlocksWithImage:image imageData:nil error:nil finished:NO];
-            }
-        });
+        if (self.coderQueue.operationCount == 0) {
+            // NSOperation have autoreleasepool, don't need to create extra one
+            @weakify(self);
+            [self.coderQueue addOperationWithBlock:^{
+                @strongify(self);
+                if (!self) {
+                    return;
+                }
+                // When cancelled or transfer finished (`didCompleteWithError`), cancel the progress callback, only completed block is called and enough
+                if (self.isCancelled || SDWebImageDownloaderOperationGetCompleted(self)) {
+                    return;
+                }
+                UIImage *image = SDImageLoaderDecodeProgressiveImageData(imageData, self.request.URL, NO, self, [[self class] imageOptionsFromDownloaderOptions:self.options], self.context);
+                if (image) {
+                    // We do not keep the progressive decoding image even when `finished`=YES. Because they are for view rendering but not take full function from downloader options. And some coders implementation may not keep consistent between progressive decoding and normal decoding.
+                    
+                    [self callCompletionBlocksWithImage:image imageData:nil error:nil finished:NO];
+                }
+            }];
+        }
     }
     
     for (SDWebImageDownloaderOperationToken *token in tokens) {
@@ -556,9 +561,11 @@ didReceiveResponse:(NSURLResponse *)response
                     [self callCompletionBlocksWithError:self.responseError];
                     [self done];
                 } else {
+                    // decode the image in coder queue, cancel all previous decoding process
+                    [self.coderQueue cancelAllOperations];
                     @weakify(self);
                     for (SDWebImageDownloaderOperationToken *token in tokens) {
-                        dispatch_async(self.coderQueue, ^{
+                        [self.coderQueue addOperationWithBlock:^{
                             @strongify(self);
                             if (!self) {
                                 return;
@@ -596,16 +603,23 @@ didReceiveResponse:(NSURLResponse *)response
                             } else {
                                 [self callCompletionBlockWithToken:token image:image imageData:imageData error:nil finished:YES];
                             }
-                        });
+                        }];
                     }
                     // call [self done] after all completed block was dispatched
-                    dispatch_async(self.coderQueue, ^{
+                    dispatch_block_t doneBlock = ^{
                         @strongify(self);
                         if (!self) {
                             return;
                         }
                         [self done];
-                    });
+                    };
+                    if (@available(iOS 13, tvOS 13, macOS 10.15, watchOS 6, *)) {
+                        // seems faster than `addOperationWithBlock`
+                        [self.coderQueue addBarrierBlock:doneBlock];
+                    } else {
+                        // serial queue, this does the same effect in semantics
+                        [self.coderQueue addOperationWithBlock:doneBlock];
+                    }
                 }
             } else {
                 [self callCompletionBlocksWithError:[NSError errorWithDomain:SDWebImageErrorDomain code:SDWebImageErrorBadImageData userInfo:@{NSLocalizedDescriptionKey : @"Image data is nil"}]];