Randy,
Thanks for reviewing the code!
My comments embedded.
I'll re-send the patches as soon as possible.
Regards,
Nadia
Randy Dunlap wrote:
On Tue, 16 Jan 2007 07:15:17 +0100 [email protected] wrote:
[PATCH 01/06]
<snip>
+Any kernel subsystem that has registered a tunable should call
+auto_tune_func() as follows:
+
++-------------------------+--------------------------------------------+
+| Step | Routine to call |
++-------------------------+--------------------------------------------+
+| Declaration phase | DEFINE_TUNABLE(name, values...); |
++-------------------------+--------------------------------------------+
+| Initialization routine | set_tunable_min_max(name, min, max); |
+| | set_autotuning_routine(name, routine); |
+| | register_tunable(&name); |
+| Note: the 1st 2 calls | |
+| are optional | |
++-------------------------+--------------------------------------------+
+| Alloc | activate_auto_tuning(AKT_UP, &name); |
++-------------------------+--------------------------------------------+
+| Free | activate_auto_tuning(AKT_DOWN, &name); |
So does Free always use AKT_DOWN? why does it matter?
Seems unneeded and inconsistent.
Tuning down is recommended in order to come back to the default tunable
value.
I agree with you: today it has quite no effect, except on the tunable
value. If we take the ipc's example, grow_ary() just returns if the new
tunable value happens to be lower than the previous one.
But we can imagine, in the future, that grow_ary could deallocate the
unused memory.
+ in that particular case, lowering the tunable value makes the 1st loop
in ipc_addid() shorter.
How does one activate a tunable for downward adjustment?
Actually a tunable is activated to be dynamically adjusted (whatever the
direction).
But you are giving me an idea for a future enhancement: we can imagine a
tunable that could be allowed to increase only (or decrease only). In
that case, we should move the autotune sysfs attribute into an 'up' and
a 'down' attribute?
<snip>
+
+2) User part:
+
+As seen above, the only way to activate automatic tuning is from user side:
+- the directory /sys/tunables is created during the init phase.
+- each time a tunable is registered by a kernel subsystem, a directory is
+created for it under /sys/tunables.
+- This directory contains 1 file for each tunable kobject attribute:
Please try to limit text documentation to 80 columns or less.
That's exactly what I did?
<snip>
Index: linux-2.6.20-rc4/fs/Kconfig
===================================================================
--- linux-2.6.20-rc4.orig/fs/Kconfig 2007-01-15 13:08:14.000000000 +0100
+++ linux-2.6.20-rc4/fs/Kconfig 2007-01-15 14:20:20.000000000 +0100
@@ -925,6 +925,8 @@ config PROC_KCORE
bool "/proc/kcore support" if !ARM
depends on PROC_FS && MMU
+source "kernel/autotune/Kconfig"
Why is that is the File systems menu? Seems odd to me
for it to be there. If it's just because it depends on
PROC_FS and SYSFS, then it should just go completely after
the File systems menu.
Since the tunables that are handled in AKT, I wanted the feature to be
close to CONFIG_PROC_FS.
Now, I do not agree with your proposal: putting it after the FS menu
means that it would appear in the main menu, right? I'll try to find a
better place for it.
Index: linux-2.6.20-rc4/include/linux/akt.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.20-rc4/include/linux/akt.h 2007-01-15 14:26:24.000000000 +0100
@@ -0,0 +1,186 @@
+
<snip>
+ char flags; /* Only 2 bits are meaningful: */
Make flags unsigned char so that no sign bit is needed.
+ /* bit 0: set to 1 if the associated tunable can */
+ /* be automatically adjusted */
+ /* bits 1: set to 1 if the tunable has been */
+ /* registered */
+ /* bits 2-7: useless */
unused ??
yep
<snip>
+
+extern void fork_late_init(void);
Looks like the wrong header file for that extern.
Actually, I wanted the changes to the existing kernel files to be as
small as possible. That's why everything is concentrated, whenever
possible, in the added files.
Regards,
Nadia
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