oss持续上传iOS端内存无法释放

我们在iOS平台上有一个直播功能，我们测试发现，在上传oss的部分上传的数据会一直存在在内存中无法释放。
-(void) updateMainifestOnServer : (NSData ) data : (NSString ) streamName : (NSString *)filename
{

//NSData *fileContent = [NSData dataWithContentsOfFile:self.manifestPath];
OSSPutObjectRequest * put = [OSSPutObjectRequest new];
put.bucketName = self.stream.bucket;
//put.objectKey = [@"file_test/" stringByAppendingFormat:@"%ld/live/%ld/%@",[self.stream getOwnerID],[self.stream getStreamID],filename];
put.objectKey = [self.stream.storage stringByAppendingString:filename];
put.uploadingData = data;
put.contentType = @"application/vnd.apple.mpegurl";
put.cacheControl =@"no-cache";
OSSTask * putTask = [_ossClient putObject:put];
__weak id weakself = self;
[putTask continueWithBlock:^id(OSSTask *task) {
    if (!task.error) {
        NSLog(@"upload manifest success!");
    } else {
        NSLog(@"upload manifest failed, error: %@" , task.error);
    }
    [weakself s3RequestCompletedForFileName:filename];
    return nil;
}];

}
次方法每5秒执行一次，instrumens显示此处的fileContent没有释放，应该是OSSPutObjectRequest没有释放的缘故吧，大家给点思路吧。