Date: Fri, 23 Dec 2016 02:02:35 +1100 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: hhsheng@corp.netease.com Cc: freebsd-questions@freebsd.org Subject: Re: question about fopen fd limit Message-ID: <20161223015110.X26979@sola.nimnet.asn.au> In-Reply-To: <mailman.109.1482408002.12273.freebsd-questions@freebsd.org> References: <mailman.109.1482408002.12273.freebsd-questions@freebsd.org>
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In freebsd-questions Digest, Vol 655, Issue 4, Message: 10
On Thu, 22 Dec 2016 11:53:08 +0800 ??? <hhsheng@corp.netease.com> wrote:
> hi all,
>
> hi~
> we are from Chinese Game Develop Corp, Netease.
> and One of our product using FreeBsd as its OS platform.
> This Game has Millions of players online , and Each Server may
> holds 25000+ tcp connection at the same time.Thanks to BSD and kqueue
> :)
>
> for example, it's one of our server , netstat cmd to list
> connections overall...
> netstat -an | grep 13396 (it's our listening port) | wc -l
> 23221
>
> recently we do some performance optimize and promote this connect
> limit to 28000+ or 30000+.
> But we find Freebsd has a limit that this huge online number will
> take 28000+ fd, and bsd FILE * struct's fd only support to SHORT .
> such as ..
>
> struct __sFILE {
> ...
> short _file; /* (*) fileno, if Unix descriptor, else -1 */
> ...
>
> so if our server want to fopen some file when we still hold this
> online number, the fd amount may easily exceed 32767, and fopen
> definitely return a err code. then the server will appear some fataly
> ERROR.
>
> we do a simple test and confirm this situation.
>
> then in fopen's code , we notice that we can use open to return a
> fd instread of fopen to avoid this overflow, as below
>
> 68 /*
> 1 * File descriptors are a full int, but _file is only a short.
> 2 * If we get a valid file descriptor that is greater than
> 3 * SHRT_MAX, then the fd will get sign-extended into an
> 4 * invalid file descriptor. Handle this case by failing the
> 5 * open.
> 6 */
>
>
> BUT ... so many c lib FILE series function needs a FILE * pointer
> as input argument, we can't convert all of them to fd, or it will be
> a rather suffering things to us.
>
> and even in BSD 10 , it seems this short limit still there , but
> other OS as debian , FILE strucnt's fileno is a int .
>
> we found an unoffical patch easily change this fileno to unsigned ,
> but we are a very stready project, we can't afford the risk to use an
> unoffical patch.
>
> so, do you have any plan to change this fopen fd limit to UNSIGNED
> SHORT or int in the future ? ushort is enough for us .
> if you do , we are really glad and excited~~~~~~~if you don't ,it
> donen't matter, plz give us a reply so that we may need to
> find some other plan to resolved this suffering thing.
> LoL, thank you !!!!!
>
> yours sincerely
> winson sheng
If you do not get a useful response here, I recommend reposting this to
freebsd-net@freebsd.org where it will much more likely catch the eye of
people who work with network code.
cheers, Ian
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