From 95878586ec7611791f4001a4ee17abf943fae3c1 Mon Sep 17 00:00:00 2001 From: "https://me.yahoo.com/a/g3Ccalpj0NhN566pHbUl6i9QF0QEkrhlfPM-#b1c14" Date: Mon, 16 Feb 2015 20:08:03 +0100 Subject: rename open_issues.mdwn to service_solahart_jakarta_selatan__082122541663.mdwn --- .../dbus_in_linux_kernel.mdwn | 164 +++++++++++++++++++++ 1 file changed, 164 insertions(+) create mode 100644 service_solahart_jakarta_selatan__082122541663/dbus_in_linux_kernel.mdwn (limited to 'service_solahart_jakarta_selatan__082122541663/dbus_in_linux_kernel.mdwn') diff --git a/service_solahart_jakarta_selatan__082122541663/dbus_in_linux_kernel.mdwn b/service_solahart_jakarta_selatan__082122541663/dbus_in_linux_kernel.mdwn new file mode 100644 index 00000000..6f83db03 --- /dev/null +++ b/service_solahart_jakarta_selatan__082122541663/dbus_in_linux_kernel.mdwn @@ -0,0 +1,164 @@ +[[!meta copyright="Copyright © 2010, 2013, 2014 Free Software Foundation, +Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!meta title="AF_BUS, D-Bus, and the Linux kernel"]] + +Might be interesting to watch how this develops. + +[[!toc]] + + +# IRC, freenode, #hurd, about 2010-08/2010-09 + + check this out: + someone is working on implementing dbus in linux + linux finally gets mach ipc ;-) + it's old news though, unless there is an update + and I think it was only the client? + youpi : someone is adding dbus ipc to the linux kernel + marcusb: I just heard about it. + (it's crazy how this drives backward compared to a hurdish approach) + what is the motivation for moving to the kernel? + context switch overhead + they wanna use it to talk to device drivers? :) + well, they did that with the in-kernel web server, but they + abandonned it later on + azeem: I don't think so. + dbus in the kernel is actually good for the Hurd as dbus IPC is + basically neutered Mach IPC + I don't think anybody wants to put the dbus server in the kernel + well, there is at least one person + maybe this is a different news from the one I read + Alban Crequy (albanc) is working out. He works for collabora, fwiw + + + + what I read was about hal etc + so that you don't need a user space daemon to glue the kernel to the + dbus world + I don't think that is what he is talking about + I can't find it anymore though. I mentioned it in this channel at + the time though, so it should be in the backlog + neal, yeah could very well be a separate thing + neal, dbus does have marginal support for fd passing though, and some + attempts on the mailing list to make "fds" an official type in the message + failed (as far as I could see, I didn't read the whole discussion) + so no mach ipc just yet + wrong + FD handling is in 1.4 + type o, if I'm not mistaken + then the discussion moved on from initial rejection + no, 'h' + I'm out of date by two months + ok + neal: AFAIR Marcel Holtmann talked about dbus in-kernel several years + ago, but he never ended up implementing it, or there were rumors he had + private "working code" + + * Related Mailing List Discussion + + * [\[PATCH 0/5\] RFC: Multicast and filtering features on + AF_UNIX](http://article.gmane.org/gmane.linux.kernel/1040481), + 2010-09-24 + + +# 2013-02 + +[AF_BUS, D-Bus, and the Linux +kernel](http://www.kroah.com/log/linux/af_bus.html), Greg Kroah-Hartman, +2013-02-08. + + +# kdbus + + +## IRC, freenode, #hurd, 2014-01-28 + + i would like to see things like dbus and zeromq use an optimized + microkernel transport one day + we could port kdbus >,< + why not + you port cgroups first + exactly + :p + +[[systemd]]. + + +## IRC, freenode, #hurd, 2014-02-23 + +In context of [[linux_as_the_kernel]], *IRC, freenode, #hurd, 2014-02-23*. + + mach seems like this really simple thing when you first explain + what a microkernel is + and because of that, i think it's better to start the right + solution directly + it looks simple, it's clearly not + but i did a bit of looking into it... it's a bit non-trivial after + all :) + mach ipc is over complicated and error prone + it leads to unefficient communication compared to other solutions + such as what l4 does + ya -- i hear that this is a big part of the performance hit + that's why i've started x15 + i was also doing some reading about how it's based on mapping + memory segments between processes + first, it was a mach clone, but since i've come to know mach + better, it's now a "spiritual" mach successor .. :) + these are two issues that we've been dealing with at another + level... in the design of kdbus + ah kdbus :) + this is something that started with my masters thesis a long time + ago... + ah you too + first thing we did is make the serialisation format so that all + messages are valid and therefore never need to be checked + (old dbus format requires checks at every step on the way) + looks interesting + then of course we cut the daemon out + but some other interesting things: security is super-simple... it's + based enirely on endpoints + either you're allowed to send messages between two processes or + you're not + there is no checking for message types, for example + yes + and the other thing: memory mapping is usually bad + that's what i mean when i say mach ipc is over complicated + it depends + the kdbus guys did some performance testing and found out that if + the message is less than ~512k then the cost of invalidating the TLB in + order to change the memory mapping is higher than the cost of just + copying the data + yes, we know that too + that's why zero copy isn't the normal way of passing small amounts + of data over mach either + nice + i got the impression in some of my reading (wikipedia, honestly) + that memory mapping was being done all the time + well + no it's not + memory mapping is unfortunately a small fraction of the + performance overhead + that's good :) + that being said + memory mapping can be very useful + for example, it's hard for us to comply with posix requirements of + being able to read/write at least 2G of data in a single call + weird bugs occur beyond 512M iirc + you do want memory mapping for that + ya... for things of this size.... you don't want to copy that + through a socket :) + monolithic kernels have it naturally, since the kernel is mapped + everywhere + for microkernels, it's a little more complicated + and the problem gets worse on smp + again, that's why i preferred starting a new kernel instead of + reusing linux -- cgit v1.2.3