diff --git a/trunk/research/arm/pipe_fds.cpp b/trunk/research/arm/pipe_fds.cpp
deleted file mode 100644
index d1c024f51..000000000
--- a/trunk/research/arm/pipe_fds.cpp
+++ /dev/null
@@ -1,48 +0,0 @@
-/**
-g++ pipe_fds.cpp -g -O0 -o pipe_fds
-
-About the limits:
-[winlin@dev6 srs]$ ulimit -n
-    1024
-[winlin@dev6 srs]$ sudo lsof -p 21182
-    pipe_fds 21182 winlin    0u   CHR  136,4      0t0       7 /dev/pts/4
-    pipe_fds 21182 winlin    1u   CHR  136,4      0t0       7 /dev/pts/4
-    pipe_fds 21182 winlin    2u   CHR  136,4      0t0       7 /dev/pts/4
-    pipe_fds 21182 winlin    3r  FIFO    0,8      0t0  464543 pipe
-    pipe_fds 21182 winlin 1021r  FIFO    0,8      0t0  465052 pipe
-    pipe_fds 21182 winlin 1022w  FIFO    0,8      0t0  465052 pipe
-So, all fds can be open is <1024, that is, can open 1023 files.
-The 0, 1, 2 is opened file, so can open 1023-3=1020files, 
-Where 1020/2=512, so we can open 512 pipes.
-*/
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <errno.h>
-#include <string.h>
-
-int main(int argc, char** argv)
-{
-    if (argc <= 1) {
-        printf("Usage: %s <nb_pipes>\n"
-            "   nb_pipes the pipes to open.\n"
-            "For example:\n"
-            "   %s 1024\n", argv[0], argv[0]);
-        exit(-1);
-    }
-    
-    int nb_pipes = ::atoi(argv[1]);
-    for (int i = 0; i < nb_pipes; i++) {
-        int fds[2];
-        if (pipe(fds) < 0) {
-            printf("failed to create pipe. i=%d, errno=%d(%s)\n", 
-                i, errno, strerror(errno));
-            break;
-        }
-    }
-    
-    printf("Press CTRL+C to quit, use bellow command to show the fds opened:\n");
-    printf("    sudo lsof -p %d\n", getpid());
-    sleep(-1);
-    return 0;
-}