From 9b1d82fa1611706fa7ee1505f290160a18caf95d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 25 Oct 2009 19:03:50 -0700 Subject: rcu: "Tiny RCU", The Bloatwatch Edition This patch is a version of RCU designed for !SMP provided for a small-footprint RCU implementation. In particular, the implementation of synchronize_rcu() is extremely lightweight and high performance. It passes rcutorture testing in each of the four relevant configurations (combinations of NO_HZ and PREEMPT) on x86. This saves about 1K bytes compared to old Classic RCU (which is no longer in mainline), and more than three kilobytes compared to Hierarchical RCU (updated to 2.6.30): CONFIG_TREE_RCU: text data bss dec filename 183 4 0 187 kernel/rcupdate.o 2783 520 36 3339 kernel/rcutree.o 3526 Total (vs 4565 for v7) CONFIG_TREE_PREEMPT_RCU: text data bss dec filename 263 4 0 267 kernel/rcupdate.o 4594 776 52 5422 kernel/rcutree.o 5689 Total (6155 for v7) CONFIG_TINY_RCU: text data bss dec filename 96 4 0 100 kernel/rcupdate.o 734 24 0 758 kernel/rcutiny.o 858 Total (vs 848 for v7) The above is for x86. Your mileage may vary on other platforms. Further compression is possible, but is being procrastinated. Changes from v7 (http://lkml.org/lkml/2009/10/9/388) o Apply Lai Jiangshan's review comments (aside from might_sleep() in synchronize_sched(), which is covered by SMP builds). o Fix up expedited primitives. Changes from v6 (http://lkml.org/lkml/2009/9/23/293). o Forward ported to put it into the 2.6.33 stream. o Added lockdep support. o Make lightweight rcu_barrier. Changes from v5 (http://lkml.org/lkml/2009/6/23/12). o Ported to latest pre-2.6.32 merge window kernel. - Renamed rcu_qsctr_inc() to rcu_sched_qs(). - Renamed rcu_bh_qsctr_inc() to rcu_bh_qs(). - Provided trivial rcu_cpu_notify(). - Provided trivial exit_rcu(). - Provided trivial rcu_needs_cpu(). - Fixed up the rcu_*_enter/exit() functions in linux/hardirq.h. o Removed the dependence on EMBEDDED, with a view to making TINY_RCU default for !SMP at some time in the future. o Added (trivial) support for expedited grace periods. Changes from v4 (http://lkml.org/lkml/2009/5/2/91) include: o Squeeze the size down a bit further by removing the ->completed field from struct rcu_ctrlblk. o This permits synchronize_rcu() to become the empty function. Previous concerns about rcutorture were unfounded, as rcutorture correctly handles a constant value from rcu_batches_completed() and rcu_batches_completed_bh(). Changes from v3 (http://lkml.org/lkml/2009/3/29/221) include: o Changed rcu_batches_completed(), rcu_batches_completed_bh() rcu_enter_nohz(), rcu_exit_nohz(), rcu_nmi_enter(), and rcu_nmi_exit(), to be static inlines, as suggested by David Howells. Doing this saves about 100 bytes from rcutiny.o. (The numbers between v3 and this v4 of the patch are not directly comparable, since they are against different versions of Linux.) Changes from v2 (http://lkml.org/lkml/2009/2/3/333) include: o Fix whitespace issues. o Change short-circuit "||" operator to instead be "+" in order to fix performance bug noted by "kraai" on LWN. (http://lwn.net/Articles/324348/) Changes from v1 (http://lkml.org/lkml/2009/1/13/440) include: o This version depends on EMBEDDED as well as !SMP, as suggested by Ingo. o Updated rcu_needs_cpu() to unconditionally return zero, permitting the CPU to enter dynticks-idle mode at any time. This works because callbacks can be invoked upon entry to dynticks-idle mode. o Paul is now OK with this being included, based on a poll at the Kernel Miniconf at linux.conf.au, where about ten people said that they cared about saving 900 bytes on single-CPU systems. o Applies to both mainline and tip/core/rcu. Signed-off-by: Paul E. McKenney Acked-by: David Howells Acked-by: Josh Triplett Reviewed-by: Lai Jiangshan Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: avi@redhat.com Cc: mtosatti@redhat.com LKML-Reference: <12565226351355-git-send-email-> Signed-off-by: Ingo Molnar --- init/Kconfig | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'init/Kconfig') diff --git a/init/Kconfig b/init/Kconfig index 09c5c64..d367bf6 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -334,6 +334,15 @@ config TREE_PREEMPT_RCU is also required. It also scales down nicely to smaller systems. +config TINY_RCU + bool "UP-only small-memory-footprint RCU" + depends on !SMP + help + This option selects the RCU implementation that is + designed for UP systems from which real-time response + is not required. This option greatly reduces the + memory footprint of RCU. + endchoice config RCU_TRACE -- cgit v1.1 From 6beb000923882f6204ea2cfcd932e568e900803f Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 9 Nov 2009 15:21:34 +0000 Subject: locking: Make inlining decision Kconfig based commit 892a7c67 (locking: Allow arch-inlined spinlocks) implements the selection of which lock functions are inlined based on defines in arch/.../spinlock.h: #define __always_inline__LOCK_FUNCTION Despite of the name __always_inline__* the lock functions can be built out of line depending on config options. Also if the arch does not set some inline defines the generic code might set them; again depending on config options. This makes it unnecessary hard to figure out when and which lock functions are inlined. Aside of that it makes it way harder and messier for -rt to manipulate the lock functions. Convert the inlining decision to CONFIG switches. Each lock function is inlined depending on CONFIG_INLINE_*. The configs implement the existing dependencies. The architecture code can select ARCH_INLINE_* to signal that it wants the corresponding lock function inlined. ARCH_INLINE_* is necessary as Kconfig ignores "depends on" restrictions when a config element is selected. No functional change. Signed-off-by: Thomas Gleixner LKML-Reference: <20091109151428.504477141@linutronix.de> Acked-by: Heiko Carstens Reviewed-by: Ingo Molnar Acked-by: Peter Zijlstra --- init/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'init/Kconfig') diff --git a/init/Kconfig b/init/Kconfig index 9e03ef8..06863dd 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1210,3 +1210,4 @@ source "block/Kconfig" config PREEMPT_NOTIFIERS bool +source "kernel/Kconfig.locks" -- cgit v1.1 From e9438e3193a0d1430b70fafe46855c1a56202f7c Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Tue, 1 Dec 2009 13:17:50 -0800 Subject: sysfs: fix SYSFS_DEPRECATED_V2 prompt The SYSFS_DEPRECATED_V2 says "remove" older, deprecated features, but it actually enables them, so correct this confusing, backwards text. Signed-off-by: Randy Dunlap Cc: Kay Sievers Cc: Greg KH Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'init/Kconfig') diff --git a/init/Kconfig b/init/Kconfig index 39923cc..eb4b337 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -606,7 +606,7 @@ config SYSFS_DEPRECATED bool config SYSFS_DEPRECATED_V2 - bool "remove sysfs features which may confuse old userspace tools" + bool "enable deprecated sysfs features which may confuse old userspace tools" depends on SYSFS default n select SYSFS_DEPRECATED -- cgit v1.1