big xml multithreading loading and parsing

i'm trying to download and parse big xml file, and using for this libxml, so i'm looking for a apple example called LibXMLParser and my problem is that cpu always 110% and on 120k objects is faults.

[NSThread detachNewThreadSelector:@selector(downloadAndParse:) toTarget:self withObject:url];

- (void)downloadAndParse:(NSURL *)url {

        self.characterBuffer = [NSMutableData data];
        NSURLRequest *theRequest = [NSURLRequest requestWithURL:url];
        self.connection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
        context = xmlCreatePushParserCtxt(&simpleSAXHandlerStruct, (__bridge void *)(self), NULL, 0, NULL);
        if (self.connection != nil) {
            do {
                [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
            } while (!self.done);
        }
        // Release resources used only in this thread.
        xmlFreeParserCtxt(context);
        self.characterBuffer = nil;
        self.parseFormatter = nil;
        self.connection = nil;
        self.currentItem = nil;
}

loading a made with this way:

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    xmlParseChunk(context, (const char *)[data bytes], [data length], 0); 
}

2014-08-05 02:35:42.130 Zarubin[13257:3503] *** Assertion failure in void errorEncounteredSAX(void *, const char *, ...)(), /Users/vitaliyzarubin/Documents/Apps/My/TestWork/Zarubin/Zarubin/LibXMLParser.m:250
2014-08-05 02:35:42.132 Zarubin[13257:3503] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unhandled error encountered during SAX parse.'
*** First throw call stack:
(
    0   CoreFoundation                      0x0269d1e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x0241c8e5 objc_exception_throw + 44
    2   CoreFoundation                      0x0269d048 +[NSException raise:format:arguments:] + 136
    3   Foundation                          0x020c8b20 -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:] + 101
    4   Zarubin                             0x00007341 errorEncounteredSAX + 225
    5   libxml2.2.dylib                     0x00f95ed1 __xmlRaiseError + 1279
    6   libxml2.2.dylib                     0x00faafe4 xmlFatalErr + 341
    7   libxml2.2.dylib                     0x00fbad4b xmlParseChunk + 967
    8   Zarubin                             0x000068f9 -[LibXMLParser connection:didReceiveData:] + 201
    9   Foundation                          0x021e5e80 ___NSURLConnectionDidReceiveData_block_invoke + 50
    10  Foundation                          0x0217c7e1 __65-[NSURLConnectionInternal _withConnectionAndDelegate:onlyActive:]_block_invoke + 62
    11  Foundation                          0x02004f5e -[NSURLConnectionInternalConnection invokeForDelegate:] + 119
    12  Foundation                          0x02004ec6 -[NSURLConnectionInternal _withConnectionAndDelegate:onlyActive:] + 208
    13  Foundation                          0x02004dd8 -[NSURLConnectionInternal _withActiveConnectionAndDelegate:] + 76
    14  Foundation                          0x02005158 _NSURLConnectionDidReceiveData + 87
    15  CFNetwork                           0x0032e171 ___ZN27URLConnectionClient_Classic29_delegate_didReceiveDataArrayEv_block_invoke + 304
    16  CFNetwork                           0x0032d3de ___ZN27URLConnectionClient_Classic18_withDelegateAsyncEPKcU13block_pointerFvP16_CFURLConnectionPK33CFURLConnectionClientCurrent_VMaxE_block_invoke_2 + 104
    17  CoreFoundation                      0x0263ec69 CFArrayApplyFunction + 57
    18  CFNetwork                           0x00296441 _ZN19RunloopBlockContext7performEv + 155
    19  CFNetwork                           0x003783f4 _ZThn16_N19RunloopBlockContext24multiplexerClientPerformEv + 20
    20  CFNetwork                           0x00296257 _ZN17MultiplexerSource7performEv + 299
    21  CFNetwork                           0x0029606c _ZN17MultiplexerSource8_performEPv + 76
    22  CoreFoundation                      0x0262677f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
    23  CoreFoundation                      0x0262610b __CFRunLoopDoSources0 + 235
    24  CoreFoundation                      0x026431ae __CFRunLoopRun + 910
    25  CoreFoundation                      0x026429d3 CFRunLoopRunSpecific + 467
    26  CoreFoundation                      0x026427eb CFRunLoopRunInMode + 123
    27  Foundation                          0x02078e35 -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 284
    28  Zarubin                             0x00006706 -[LibXMLParser downloadAndParse:] + 550
    29  Foundation                          0x02073a07 -[NSThread main] + 76
    30  Foundation                          0x02073966 __NSThread__main__ + 1275
    31  libsystem_pthread.dylib             0x030ff21f _pthread_body + 138
    32  libsystem_pthread.dylib             0x030ff195 _pthread_body + 0
    33  libsystem_pthread.dylib             0x030fd2fe thread_start + 34
)