From: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
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To: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> |
Cc: | <robertmhaas(at)gmail(dot)com>, <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Escaping from blocked send() reprised. |
Date: | 2014-09-02 18:22:29 |
Message-ID: | 54060AE5.5020502@vmware.com |
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Lists: | pgsql-hackers |
On 08/28/2014 03:47 PM, Kyotaro HORIGUCHI wrote:
> To make the code mentioned above (Patch 0002) tidy, rewrite the
> socket emulation code for win32 backends so that each socket
> can have its own non-blocking state. (patch 0001)
The first patch that makes non-blocking sockets behave more sanely on
Windows seems like a good idea, independently of the second patch. I'm
looking at the first patch now, I'll make a separate post about the
second patch.
> Some concern about this patch,
>
> - This patch allows the number of non-blocking socket to be below
> 64 (FD_SETSIZE) on win32 backend but it seems to be sufficient.
Yeah, that's plenty.
> - This patch introduced redundant socket emulation for win32
> backend but win32 bare socket for Port is already nonblocking
> as described so it donsn't seem to be a serious problem on
> performance. Addition to it, since I don't know the reason why
> win32/socket.c provides the blocking-mode socket emulation, I
> decided to preserve win32/socket.c to have blocking socket
> emulation. Possibly it can be removed.
On Windows, the backend has an emulation layer for POSIX signals, which
uses threads and Windows events. The reason win32/socket.c always uses
non-blocking mode internally is that it needs to wait for the socket to
become readable/writeable, and for the signal-emulation event, at the
same time. So no, we can't remove it.
The approach taken in the first patch seems sensible. I changed it to
not use FD_SET, though. A custom array seems better, that way we don't
need the pgwin32_nonblockset_init() call, we can just use initialize the
variable. It's a little bit more code, but it's well-contained in
win32/socket.c. Please take a look, to double-check that I didn't screw up.
- Heikki
Attachment | Content-Type | Size |
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improve-nonblocking-sockets-on-windows-1.patch | text/x-diff | 7.9 KB |
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