Try to make students think about performance of scheduler dispatching.

[pintos-anon] / doc / threads.texi

diff --git a/doc/threads.texi b/doc/threads.texi
index 1093f335636dcc13c85e3bebe944129d97c7beae..a28d7a41d1c14842c8ee65a8ca3bf26c177c4ff8 100644 (file)
--- a/doc/threads.texi
+++ b/doc/threads.texi
@@ -76,11 +76,11 @@ assembly code.  (You don't have to understand it.)  It saves the
 state of the currently running thread and restores the state of the
 thread we're switching to.
 
-Using the @command{gdb} debugger, slowly trace through a context
-switch to see what happens (@pxref{gdb}).  You can set a
+Using the GDB debugger, slowly trace through a context
+switch to see what happens (@pxref{GDB}).  You can set a
 breakpoint on @func{schedule} to start out, and then
-single-step from there.@footnote{@command{gdb} might tell you that
-@func{schedule} doesn't exist, which is arguably a @command{gdb} bug.
+single-step from there.@footnote{GDB might tell you that
+@func{schedule} doesn't exist, which is arguably a GDB bug.
 You can work around this by setting the breakpoint by filename and
 line number, e.g.@: @code{break thread.c:@var{ln}} where @var{ln} is
 the line number of the first declaration in @func{schedule}.}  Be sure
@@ -185,8 +185,8 @@ project 3.  For now, you can ignore it.
 
 @item flags.h
 Macros that define a few bits in the 80@var{x}86 ``flags'' register.
-Probably of no interest.  See @bibref{IA32-v1}, section 3.4.3, for more
-information.
+Probably of no interest.  See @bibref{IA32-v1}, section 3.4.3, ``EFLAGS
+Register,'' for more information.
 @end table
 
 @menu
@@ -328,9 +328,10 @@ timer ticks or input events.  Turning off interrupts also increases the
 interrupt handling latency, which can make a machine feel sluggish if
 taken too far.
 
-You may need to add or modify code where interrupts are already
-disabled, such as in @func{sema_up} or @func{sema_down}.  You should
-still try to keep this code as short as you can.
+The synchronization primitives themselves in @file{synch.c} are
+implemented by disabling interrupts.  You may need to increase the
+amount of code that runs with interrupts disabled here, but you should
+still try to keep it to a minimum.
 
 Disabling interrupts can be useful for debugging, if you want to make
 sure that a section of code is not interrupted.  You should remove
@@ -441,8 +442,8 @@ priority such that it no longer has the highest priority must cause it
 to immediately yield the CPU.
 
 Thread priorities range from @code{PRI_MIN} (0) to @code{PRI_MAX} (63).
-Lower numbers correspond to @emph{higher} priorities, so that priority 0
-is the highest priority and priority 63 is the lowest.
+Lower numbers correspond to lower priorities, so that priority 0
+is the lowest priority and priority 63 is the highest.
 The initial thread priority is passed as an argument to
 @func{thread_create}.  If there's no reason to choose another
 priority, use @code{PRI_DEFAULT} (31).  The @code{PRI_} macros are
@@ -511,7 +512,8 @@ must be active, but we must be able to choose the 4.4@acronym{BSD}
 scheduler
 with the @option{-mlfqs} kernel option.  Passing this
 option sets @code{enable_mlfqs}, declared in @file{threads/init.h}, to
-true.
+true when the options are parsed by @func{parse_options}, which happens
+midway through @func{main}.
 
 When the 4.4@acronym{BSD} scheduler is enabled, threads no longer
 directly control their own priorities.  The @var{priority} argument to
@@ -531,6 +533,12 @@ Here's a summary of our reference solution, produced by the
 @command{diffstat} program.  The final row gives total lines inserted
 and deleted; a changed line counts as both an insertion and a deletion.
 
+The reference solution represents just one possible solution.  Many
+other solutions are also possible and many of those differ greatly from
+the reference solution.  Some excellent solutions may not modify all the
+files modified by the reference solution, and some may modify files not
+modified by the reference solution.
+
 @verbatim
  devices/timer.c       |   42 +++++-
  threads/fixed-point.h |  120 ++++++++++++++++++
@@ -540,6 +548,8 @@ and deleted; a changed line counts as both an insertion and a deletion.
  5 files changed, 440 insertions(+), 29 deletions(-)
 @end verbatim
 
+@file{fixed-point.h} is a new file added by the reference solution.
+
 @item How do I update the @file{Makefile}s when I add a new source file?
 
 @anchor{Adding Source Files}
@@ -665,7 +675,7 @@ list.
 
 @item If the highest-priority thread yields, does it continue running?
 
-Yes.  As long as there is a single highest-priority thread, it continues
+Yes.  If there is a single highest-priority thread, it continues
 running until it blocks or finishes, even if it calls
 @func{thread_yield}.
 If multiple threads have the same highest priority,
@@ -717,4 +727,9 @@ just before the first @func{printf} in @func{main}.  Then modify
 
 It doesn't have to.  We won't test priority donation and the advanced
 scheduler at the same time.
+
+@item Can I use one queue instead of 64 queues?
+
+Yes.  In general, your implementation may differ from the description,
+as long as its behavior is the same.
 @end table