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

[Alan]

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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