[ruby-cvs:73160] normal:r66060 (trunk): io.c (rb_update_max_fd): use F_GETFL if possible

[normal at ruby-lang.org]

normal	2018-11-28 10:10:40 +0900 (Wed, 28 Nov 2018)

  New Revision: 66060

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=66060

  Log:
    io.c (rb_update_max_fd): use F_GETFL if possible
    
    On 64-bit Linux, fstat() needs to fill out a 144 byte struct
    while F_GETFL only needs to return 8 bytes.
    
    Fwiw, F_GETFD requires an additional rcu_read_lock and bitmap
    check; so it's obviously more expensive than F_GETFL on Linux.
    
    Reduce stack usage of rb_update_max_fd from 184 to 24 bytes.

  Modified files:
    trunk/io.c