[libdispatch-dev] Memory issues with libdispatch

[Aldrin Martoq Ahumada]

Hi Daniel,

I'm using Activity Monitor (OS X) and top (linux).

1) Here we have 1.9MiB initially (no SIGHUP sent yet)
http://cl.ly/2P1o3s3T0P1X0l1D390W

2) Here we have 147MiB while the loop is running (SIGHUP sent)
http://cl.ly/473x2U1v2W1h1141441k

3) Here we have 24.7MiB after everything is done
http://cl.ly/0n0S3K3t3n2C0t1y393l

4) If I send the signal again, memory increases everytime (26.0 MiB here)
http://cl.ly/0B2E2g3V021f0s2w3T2v


Memory never goes down after that, in Linux it is worst.



Thanks for the note on dispatch_async(), It was not there originally… I was trying to make it work and adding autoreleasepools just in case, but nothing seemed to work ;)



Regards,

Aldrin Martoq A.
http://aldrin.martoq.cl/

On Apr 30, 2012, at 3:07 PM, Daniel A. Steffen wrote:

> Aldrin,
> 
> how are you measuring this memory usage growth? I cannot reproduce it on Mac OS X with the 'heap' tool
> 
> You might be seeing the temporary effects of the libdispatch continuation cache, these are small buffers that get allocated for each dispatch_async() and cached on a per-thread basis for speed. That cache is freed once a temporary dispatch worker thread exits ( a couple of seconds after SIGHUP in your example, on Mac OS X at least)
> 
> Also note that there is no need to dispatch_async() from your source event handler since you are already on the main queue at that point (the target queue of the source)
> 
> Daniel
> 
> On Apr 29, 2012, at 23:09, Aldrin Martoq Ahumada <aldrin.martoq at gmail.com> wrote:
> 
>> Hi, I have been testing sample code from the wiki and found that libdispatch is alloc'ing a lot of memory without releasing it, both in OS X (Lion 10.7.3, Xcode 4.3.2) and Linux (manually compiled and installed).
>> 
>> The code creates a SIGHUP signal source, with a handler that calls 100_000 writes to a logfile. The write to a log is queued in a serial queue.
>> 
>> The first run shows normal memory usage (8-9 MiB both Linux and OS X). After sending a "kill -1 <pid>" memory usage increases 1-20MiB every time I send the SIGHUP signal.
>> 
>> I have tried compiling with -fobj-arc and without it, but the result is the same. I removed the NSString usage in the br_log function, but the leak is not there: it is somewhere inside libdispatch.
>> 
>> I tried both valgrind and Xcode Instruments, but no leaks are found. Thanks in advance,
>> 
>> 
>> ---- ini ----
>> //
>> //  main.m
>> //  test02
>> //
>> //  Created by Aldrin Martoq on 4/29/12.
>> //  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
>> //
>> 
>> #include <unistd.h>
>> #import <Foundation/Foundation.h>
>> #import <dispatch/dispatch.h>
>> 
>> static FILE *log_file = NULL;
>> static NSString *log_filename = @"/tmp/br.log";
>> static dispatch_queue_t log_queue;
>> 
>> 
>> void br_log(NSString *format, ...) {
>>     @autoreleasepool {
>>         va_list ap;
>>         va_start(ap, format);
>>         NSString *s = [[NSString alloc] initWithFormat:format arguments:ap];
>>         va_end(ap);
>>         
>>         if (log_file == NULL) {
>>             log_queue = dispatch_queue_create("cl.martoq.log_queue", NULL);
>>             
>>             log_file = fopen([log_filename cStringUsingEncoding:NSUTF8StringEncoding], "a");
>>             NSLog(@"Log file created: %@", log_filename);
>>         }
>>         
>>         dispatch_async(log_queue, ^{
>>             @autoreleasepool {
>>                 const char *c = [s cStringUsingEncoding:NSUTF8StringEncoding];
>>                 fputs(c, log_file);
>>                 fputs("\n", log_file);
>>                 fflush(log_file);
>>                 [s release];
>>             }
>>         });
>>     }
>> }
>> 
>> void br_setup() {
>>     signal(SIGHUP, SIG_IGN);
>>     dispatch_source_t sig_src = dispatch_source_create(DISPATCH_SOURCE_TYPE_SIGNAL, SIGHUP, 0, dispatch_get_main_queue());
>>     dispatch_source_set_event_handler(sig_src, ^{
>>         dispatch_async(dispatch_get_main_queue(), ^{
>>             printf("Caught SIGHUP\n");
>>             for (int i = 0; i < 100000; i++) {
>>                 br_log(@"prueba: %d", i);
>>             }
>>         });
>>     });
>>     dispatch_resume(sig_src);
>> }
>> 
>> 
>> int main(int argc, const char * argv[]) {
>>     @autoreleasepool {
>>         // insert code here...
>>         NSLog(@"Hello, World!");
>>         br_setup();
>>         dispatch_main();
>>     }
>>     return 0;
>> }
>> ---- fini ----
>> 
>> 
>> 
>> Aldrin Martoq A.
>> http://aldrin.martoq.cl/
>> 
>> _______________________________________________
>> libdispatch-dev mailing list
>> libdispatch-dev at lists.macosforge.org
>> http://lists.macosforge.org/mailman/listinfo.cgi/libdispatch-dev
> 

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