Re: [PATCH v12 04/20] index-helper: new daemon for caching index and related stuff

On 06/26/2016 04:53 AM, Eric Wong wrote:

David Turner [off-list ref] wrote:

quoted

On 06/25/2016 10:33 AM, Duy Nguyen wrote:

quoted

quoted

+               /*
+                * Our connection to the client is blocking since a client
+                * can always be killed by SIGINT or similar.
+                */
+               set_socket_blocking_flag(client_fd, 0);

Out of curiosity, do we really need this? I thought default behavior
was always blocking (and checked linux kernel, it seemed to agree with
me). Maybe for extra safety because other OSes may default to
something else?

Yes -- see this bug report for details:
https://bugs.python.org/issue7995

I realize it's an issue with BSDs, but it still seems
unnecessary, here:

1) the packet_read => get_packet_data => read_in_full => xread
    call chain already poll()s on EAGAIN/EWOULDBLOCK.
    write_in_full => xwrite busy loops on EAGAIN/EWOULDBLOCK.
    xwrite should probably poll, too; but I guess EAGAIN is
    uncommon with small writes.

That is a CPU-burning busy loop on a non-blocking socket.

2) you create the listen fd you call accept on and never set
    non-blocking on it.  It might be an issue one day if
    we use socket activation and inherit a socket, but the
    retries mentioned in 1) should cover that case.

Hm.  I wonder why I thought I had made it non-blocking.

I'm sort of reluctant to change this as I no longer have a Mac to test 
on.  Does someone else have a Mac that they can use to test this?