[Mono-dev] Problem handling more the 1024 file handle

[Robert Jordan]

On 04.11.2011 10:17, Torello Querci wrote:
> This is the first test that I realized.
> On the same machine, same kernel .... same calls ....

You don't say which Mono arch you're using. On 32 bit,
the following might not be correct:

	struct rlimit {
		public IntPtr rlimit_cur;
		public IntPtr rlimit_max;
	}

because rlim_t is 8 byte long whereas IntPtr is 4 bytes.
This is because Mono is compiled with LARGEFILE64 support.

Robert


>
> Below the source code:
>
> =====================================================================
> #include<linux/resource.h>
>
> //#include<stdlib.h>
> #include<stdio.h>
>
>
> int main(int argc, char* argv[]) {
>
>      FILE** fp;
>      int nFiles = atoi(argv[1]);
>      int i;
>      char filename[1024];
>
>      if (argc!=2) {
>          printf("Error. You need to specify the number of file that
> need to create.\n");
>          return -1;
>      }
>
>      struct rlimit data;
>
>      data.rlim_cur = 20000;
>      data.rlim_max = 20000;
>
>      i = setrlimit (RLIMIT_NOFILE,&data);
>      if (i != 0) {
>          printf ("Error during changine files limits.\n");
>          return 1;
>      }
>
>      fp = calloc (nFiles, sizeof(FILE*));
>
>      for (i=0; i<nFiles; ++i) {
>          sprintf (filename, "file%i.out", i);
>
>          fp[i] = fopen (filename, "w+");
>          if (fp [i] == NULL) {
>              printf ("Error in %s file creation.\n", filename);
>              return -1;
>          }
>      }
>
> }
>
> =============================================================
>
> 2011/11/4 Alan<alan.mcgovern at gmail.com>:
>> Hi,
>> Mono itself has no trouble opening 1000's of files. Would you be able to
>> create an equivalent C program and see if that works as expected? My guess
>> would be that the equivalent C program will fail in the same way. If it does
>> not, then it's likely to be a mono bug.
>> Alan
>>
>> On 4 November 2011 07:19, Torello Querci<tquerci at gmail.com>  wrote:
>>>
>>> Hi al,
>>>
>>> trying to handle more that 1024 handle file I got an exception even if
>>> I increase the max number of file limit using "setrlimit". The example
>>> source code below.
>>> Of course mono have the right pcap permission.
>>>
>>> Using strace on both this code and no setrlimit version code I have
>>> some differences.
>>> On the no setrlimit version I have this syscall:
>>>
>>> open("file1021.out", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = -1
>>> EMFILE (Too many open files)
>>>
>>> and this seems to be correct.
>>> On the setrlimit version code I have this syscalls:
>>>
>>> open("file1021.out", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 1024
>>> close(1024)                             = 0
>>>
>>> so seems that mono close the file because open  return value is 1024.
>>>
>>> Is this a bug, a feature, or something else?
>>>
>>>
>>> ==================================================================================================================
>>> using System;
>>> using System.IO;
>>> using System.Text;
>>> using System.Runtime.InteropServices;
>>>
>>> namespace TestFiles
>>> {
>>>
>>>         struct rlimit {
>>>                 public IntPtr rlimit_cur;
>>>                 public IntPtr rlimit_max;
>>>         }
>>>
>>>         class MainClass
>>>         {
>>>                 public static unsafe void Main (string[] args)
>>>                 {
>>>                         FileStream[] streams;
>>>                         string path;
>>>                         if (args.Length == 0) {
>>>                                 Console.WriteLine ("You need to specify the
>>> number of files that
>>> needs to be created.");
>>>                                 return;
>>>                         }
>>>
>>>                         int nFiles = Int32.Parse (args[0]);
>>>
>>>                         streams = new FileStream[nFiles];
>>>
>>>                         rlimit data = new rlimit ();
>>>                         data.rlimit_cur = (IntPtr) 20000;
>>>                         data.rlimit_max = (IntPtr) 20000;
>>>
>>>                         int result = setrlimit (RLIMIT_NOFILE,&data);
>>>                         if (result != 0) {
>>>                                 throw new Exception ("Cannot change limit
>>> on open files");
>>>                         }
>>>
>>>                         for (int i=0; i<nFiles; ++i) {
>>>                                 path = string.Format ("file{0}.out", i);
>>>                                 try {
>>>                                         streams[i] = File.Open(path,
>>> FileMode.Create, FileAccess.Write,
>>> FileShare.None);
>>>                                 } catch (Exception ex) {
>>>                                         Console.WriteLine ("Unable to write
>>> file {0}", path);
>>>                                         Console.WriteLine (ex.Message);
>>>                                         Console.WriteLine (ex.StackTrace);
>>>                                         return;
>>>                                 }
>>>                         }
>>>                 }
>>>
>>>                 const int RLIMIT_NOFILE = 7;
>>>
>>>                 [DllImport ("libc", SetLastError = true)]
>>>                 unsafe extern static int setrlimit(int resource, rlimit*
>>> rlim);
>>>
>>>         }
>>> }
>>> _______________________________________________
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>>> Mono-devel-list at lists.ximian.com
>>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>
>>