Created attachment 24850 [details]
apr-1.3.9-assume-cloexec.patch

apr_file_open currently uses O_CLOEXEC when opening file's to avoid race conditions with the classic behavior of then using fcntl() to set the FD_CLOEXEC flag.  this is all find and dandy except that on newer operating systems, the two fcntl() calls are still made even if the open() function supports O_CLOEXEC.  when doing something like `svn commit` on a large tree, these translates to a huge number of useless syscalls.

this should be easy to avoid -- if we called open() with O_CLOEXEC, and the fcntl() get step shows that FD_CLOEXEC is already set, we cache the result in a local variable.  then in all future steps, we check the cached value before doing any fcntl() syscalls.

getting back to subversion, before my fix, a simple `svn st` looks something like this:
......
open(".svn/entries", O_RDONLY|O_CLOEXEC) = 3
fcntl(3, F_GETFD)                       = 0x1 (flags FD_CLOEXEC)
fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
read(3, "10\n\ndir\n9382\nsvn://nwd2cvs1.corp"..., 80) = 80
close(3)                                = 0
open(".svn/entries", O_RDONLY|O_CLOEXEC) = 3
fcntl(3, F_GETFD)                       = 0x1 (flags FD_CLOEXEC)
fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
read(3, "10\n\ndir\n9382\nsvn://nwd2cvs1.corp"..., 4096) = 1187
read(3, "", 4096)                       = 0
read(3, "", 4096)                       = 0
close(3)                                = 0
open("vendors/.svn/entries", O_RDONLY|O_CLOEXEC) = 3
fcntl(3, F_GETFD)                       = 0x1 (flags FD_CLOEXEC)
fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
read(3, "10\n\ndir\n9382\nsvn://nwd2cvs1.corp"..., 80) = 80
close(3)                                = 0
......

and after, we see:
......
open(".svn/entries", O_RDONLY|O_CLOEXEC) = 3
fcntl(3, F_GETFD)                       = 0x1 (flags FD_CLOEXEC)
fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
read(3, "10\n\ndir\n9382\nsvn://nwd2cvs1.corp"..., 80) = 80
close(3)                                = 0
open(".svn/entries", O_RDONLY|O_CLOEXEC) = 3
read(3, "10\n\ndir\n9382\nsvn://nwd2cvs1.corp"..., 4096) = 1187
read(3, "", 4096)                       = 0
read(3, "", 4096)                       = 0
close(3)                                = 0
open("vendors/.svn/entries", O_RDONLY|O_CLOEXEC) = 3
read(3, "10\n\ndir\n9382\nsvn://nwd2cvs1.corp"..., 80) = 80
close(3)                                = 0
......

when working on a repo with thousands of dirs/files, you can see how this easily makes a significant difference.