Date: Sat, 24 Dec 2016 17:19:56 -0800 From: Alfred Perlstein <alfred@freebsd.org> To: =?UTF-8?B?55ub5oWn5Y2O?= <hhsheng@corp.netease.com>, Hongjiang Zhang <honzhan@microsoft.com>, freebsd-net <freebsd-net@freebsd.org> Subject: Re: question about fopen fd limit Message-ID: <db32b02b-2eb3-cee8-98cd-0940223f04d9@freebsd.org> In-Reply-To: <2016122316484066524625@corp.netease.com> References: <2016122223570929089978@corp.netease.com> <CY1PR03MB1517A33F8F9E0BAC00C2E345B5950@CY1PR03MB1517.namprd03.prod.outlook.com> <2016122311014089280414@corp.netease.com> <CY1PR03MB151796BFAEA5DDB1CD6DB752B5950@CY1PR03MB1517.namprd03.prod.outlook.com> <2016122316484066524625@corp.netease.com>
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Hello 盛慧华
Here's another trick that may work.
Use funopen(3) and provide your own read/write/seek and close functions
for the high fds.
You can basically make "cookie" a struct that contains your "int sized" fds.
FILE *
funopen(const void *cookie, int (*readfn)(void *, char *, int),
int (*writefn)(void *, const char *, int),
fpos_t (*seekfn)(void *, fpos_t, int), int (*closefn)(void *));
If you need more help please make sure to email me directly so I can see
your question.
-Alfred
On 12/23/16 12:48 AM, 盛慧华 wrote:
> hi all,
>
> Thank you for your advice ~
> solution 2 definitly broaden my horizons ~~but may be not a good choice for my project ~~LoL
> i will try to mail freebsd-current mail list, if libc is as your description , may be i should modify it by myself ~~
> Thank you so much~
> Are u KingSoft's Dr Zhang ? nice to meet you !!!!!
>
> winson sheng
>
>
>
> winson sheng
>
> From: Hongjiang Zhang
> Date: 2016-12-23 11:44
> To: 盛慧华; freebsd-net
> Subject: RE: RE: question about fopen fd limit
> Ok. I know.
> There are two possible solutions:
> Quick solution for short term: modify short to int in libc by yourself, buildworld and installworld. Pushing to modify libc may take a long time, especially only few people encounter this issue. You’d better send email to freebsd-current to confirm whether they accept your suggestion.
> Work around: You can first reserve a series of fd before opening TCP connections. For example, invoke open(“/dev/null”) for 10000 times to get 10000 fds. Those fd values are small enough to be held by “short”. After that, start TCP connections. Once you need to fopen a file, please call open(“xxx”) instead, and then use dup2(old_fd, new_fd) to exchange the two fd. The old_fd value is the one obtained by open(“xxx”), and new_fd is one in your reserved fd fields, and next please use fdopen(fd, mode). Here, you have to manage the reserved fds by yourself including open/close.
>
> In my eyes:
> is the quick method, and there is no modifications in your logic.
> Needs you to maintain the reserved consecutive fields for fd by yourself, which increased the complexity of your logic.
>
> Thanks
> Hongjiang Zhang
>
> From: 盛慧华 [mailto:hhsheng@corp.netease.com]
> Sent: Friday, December 23, 2016 11:02 AM
> To: Hongjiang Zhang <honzhan@microsoft.com>; freebsd-net <freebsd-net@freebsd.org>
> Subject: Re: RE: question about fopen fd limit
>
> hi all,
>
> not map TCP to FILE, you misunderstanding my meaning~
>
> for example, if my server tcp already holds 32000 connection
> fopen only has 767 fd to use
>
> the problem has no bussiness with tcp fd, BUT fopen ...
>
> in some particular situlations , my server will open 1k+ FILE , that will exceed the fileno limit, and overflow occur
> my server can't open any file more ,that's the problem ~
>
> so i felt if bsd official could change FILE struct's fileno to a UNSIGNED SHORT that may be an effecient and convenient solution just for my case ?
> UNSIGNED SHORT fileno is enough for me, and i don't wanna change a lot of FILE function that take FILE * as its argument ~
>
> Thank you ~~~
>
> winson sheng
>
>
>
>
> winson sheng
>
> From: Hongjiang Zhang
> Date: 2016-12-23 10:17
> To: 盛慧华; freebsd-net
> Subject: RE: question about fopen fd limit
> Why do you need to map TCP fd to FILE?
>
> It is difficult to modify FILE structure. If it is possible, let us figure out some new designs to meet your requirement.
>
> -----Original Message-----
> From: owner-freebsd-net@freebsd.org [mailto:owner-freebsd-net@freebsd.org] On Behalf Of ???
> Sent: Thursday, December 22, 2016 11:57 PM
> To: freebsd-net <freebsd-net@freebsd.org>
> Subject: question about fopen fd limit
>
> 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
>
>
> winson sheng
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