Date: Tue, 2 Feb 2016 12:35:47 -0800 From: Alfred Perlstein <alfred@freebsd.org> To: Xin LI <delphij@gmail.com> Cc: John Baldwin <jhb@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r295136 - in head: sys/kern sys/netinet sys/sys usr.bin/netstat Message-ID: <56B11323.70905@freebsd.org> In-Reply-To: <CAGMYy3v4s-UQpO3-oq8B1V1NvzyGSmJU49zDUL9oPy21sYkWCQ@mail.gmail.com> References: <201602020557.u125vxCP084718@repo.freebsd.org> <36439709.poT7RgRunK@ralph.baldwin.cx> <56B10D67.4050602@freebsd.org> <CAGMYy3v4s-UQpO3-oq8B1V1NvzyGSmJU49zDUL9oPy21sYkWCQ@mail.gmail.com>
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On 2/2/16 12:23 PM, Xin LI wrote: > > > On Tuesday, February 2, 2016, Alfred Perlstein <alfred@freebsd.org > <mailto:alfred@freebsd.org>> wrote: > > > > On 2/2/16 11:39 AM, John Baldwin wrote: > > On Tuesday, February 02, 2016 05:57:59 AM Alfred Perlstein wrote: > > Author: alfred > Date: Tue Feb 2 05:57:59 2016 > New Revision: 295136 > URL: https://svnweb.freebsd.org/changeset/base/295136 > > Log: > Increase max allowed backlog for listen sockets > from short to int. > PR: 203922 > Submitted by: White Knight <white_knight@2ch.net> > MFC After: 4 weeks > > You do realize that this breaks the ABI of the sysctls used to > fetch > connection lists (and so will break existing binaries like > ucd-snmpd, etc.) > and thus can't be MFC'd right? > > OK, I will not MFC it. > > Is it worthwhile to extend the xsocket to have padding so that in > 11.x and beyond we can allow for some changes in the structure? > > Another idea I had was to include a version number with the sysctl > request so that we can send back versioned structures, let me know > what you think about that. > > The first idea will take not more than a few days for me to > accomplish, the second (versioning the sysctl) probably a few more > days than that. > > > We have similar construction (versioned ioctl) in FreeBSD ZFS but the > main goal is to keep system bootable, not to support all > functionalities. Do we change the structure often and is it important > enough to warrant the complexity? I think kmem interface have a > simple size check to guard against world/kernel inconsistency. > > I would second John's comment on the necessity of the change though, > if one already have 32K of *backlogged* connections, it's probably not > very useful to allow more coming in. It sounds like the application > itself is seriously broken, and unless expanding the field have some > performance benefit, I don't think it should stay. Imagine a hugely busy image board like 2ch.net, if there is a single hiccup, it's very possible to start dropping connections. I stand by the scalability improvement offered here even though it is an edge case. Linux appears to offer 32 bits of backlog and so should we. -Alfred
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