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 --- .../system_call_mechanism.mdwn | 56 ++++++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 service_solahart_jakarta_selatan__082122541663/system_call_mechanism.mdwn (limited to 'service_solahart_jakarta_selatan__082122541663/system_call_mechanism.mdwn') diff --git a/service_solahart_jakarta_selatan__082122541663/system_call_mechanism.mdwn b/service_solahart_jakarta_selatan__082122541663/system_call_mechanism.mdwn new file mode 100644 index 00000000..68418097 --- /dev/null +++ b/service_solahart_jakarta_selatan__082122541663/system_call_mechanism.mdwn @@ -0,0 +1,56 @@ +[[!meta copyright="Copyright © 2011, 2012 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]]."]]"""]] + +[[!tag open_issue_gnumach]] + +[[!toc]] + + +# IRC, freenode, #hurd, 2011-05-07 + + very simple examples: system calls use old call gates, which are + the slowest path to kernel space + modern processors have dedicated instructions now + + +# IRC, freenode, #hurd, 2012-04-22 + + rah: basically, system calls are slower on mach because they use + call gates instead of newer sysenter/sysexit + braunr: sysenter/exit is a x86_64 thing + rah: apart from that, the code can't get much simpler, and *I* + know, for i have studied it, and wrote a compatible version in a clone + attempt + braunr: on a x86_64 port we'd probably use sysenter/exit + youpi: no there are 32-bits instructions, i don't remember if + they're called sysenter, it's in my thesis though so i'm sure of it :) + braunr: ah, the other part + is linux-x86 using them? + youpi: yes, glibc uses them + and does it really change much nowadays? + what is the actual difference between int 80 and sysenter? + less checking + checking what? + the idt? + ring levels for example + well, checking a ring is fast :) + depending on the original and requested levels, there are lookups + in tables + sysenter always assume 3 to 0 and 0 to 3 for sysexit + ah, also it assumes things about segments + so that indeed makes context things simpler + right + but mach doesn't uses int 0x80 + it uses an lcall + which is a bit slower from what I could read some time ago + (not sure if it's still relevant) + actually in 64bit mode I had to catch lcall from the invalid + instruction trap + perhaps it got dropped in 64bit mode -- cgit v1.2.3