linux-sg2042/drivers/lguest
Rusty Russell 71a3f4edc1 lguest: use get_user_pages_fast() instead of get_user_pages()
Using a simple page table thrashing program I measure a slight
improvement.  The program creates five processes.  Each touches 1000
pages then schedules the next process.  We repeat this 1000 times.  As
lguest only caches 4 cr3 values, this rebuilds a lot of shadow page
tables requiring virt->phys mappings.

	Before: 5.93 seconds
	After: 5.40 seconds

(Counts of slow vs fastpath in this usage are 6092 and 2852462 respectively.)

And more importantly for lguest, the code is simpler.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-08-12 17:52:53 +10:00
..
x86 lguest: use cpu capability accessors 2008-07-29 09:58:34 +10:00
Kconfig x86, VisWS: turn into generic arch, eliminate Kconfig specials 2008-07-10 18:55:47 +02:00
Makefile lguest: Add puppies which where previously missing. 2008-03-28 11:05:52 +11:00
README lguest: documentation I: Preparation 2007-07-26 11:35:16 -07:00
core.c lguest: fix switcher_page leak on unload 2008-07-29 09:58:32 +10:00
hypercalls.c lguest: comment documentation update. 2008-03-28 11:05:54 +11:00
interrupts_and_traps.c lguest: Guest int3 fix 2008-07-29 09:58:31 +10:00
lg.h x86/paravirt: add pte_flags to just get pte flags 2008-05-27 10:11:36 +02:00
lguest_device.c virtio: Add transport feature handling stub for virtio_ring. 2008-07-25 12:06:14 +10:00
lguest_user.c lguest: remove bogus NULL cpu check 2008-05-02 21:50:52 +10:00
page_tables.c lguest: use get_user_pages_fast() instead of get_user_pages() 2008-08-12 17:52:53 +10:00
segments.c lguest: get rid of lg variable assignments 2008-01-30 22:50:18 +11:00

README

Welcome, friend reader, to lguest.

Lguest is an adventure, with you, the reader, as Hero.  I can't think of many
5000-line projects which offer both such capability and glimpses of future
potential; it is an exciting time to be delving into the source!

But be warned; this is an arduous journey of several hours or more!  And as we
know, all true Heroes are driven by a Noble Goal.  Thus I offer a Beer (or
equivalent) to anyone I meet who has completed this documentation.

So get comfortable and keep your wits about you (both quick and humorous).
Along your way to the Noble Goal, you will also gain masterly insight into
lguest, and hypervisors and x86 virtualization in general.

Our Quest is in seven parts: (best read with C highlighting turned on)

I) Preparation
	- In which our potential hero is flown quickly over the landscape for a
	  taste of its scope.  Suitable for the armchair coders and other such
	  persons of faint constitution.

II) Guest
	- Where we encounter the first tantalising wisps of code, and come to
	  understand the details of the life of a Guest kernel.

III) Drivers
	- Whereby the Guest finds its voice and become useful, and our
	  understanding of the Guest is completed.

IV) Launcher
	- Where we trace back to the creation of the Guest, and thus begin our
	  understanding of the Host.

V) Host
	- Where we master the Host code, through a long and tortuous journey.
	  Indeed, it is here that our hero is tested in the Bit of Despair.

VI) Switcher
	- Where our understanding of the intertwined nature of Guests and Hosts
	  is completed.

VII) Mastery
	- Where our fully fledged hero grapples with the Great Question:
	  "What next?"

make Preparation!
Rusty Russell.