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

[Torello Querci]

This is the first test that I realized.
On the same machine, same kernel .... same calls ....

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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>
>