From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: [merged] remove-put_cpu_no_resched.patch removed from -mm tree Date: Wed, 17 Jun 2009 11:37:22 -0700 Message-ID: <200906171837.n5HIbMXH003456@imap1.linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:57319 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755030AbZFQSyS (ORCPT ); Wed, 17 Jun 2009 14:54:18 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: tglx@linutronix.de, Trond.Myklebust@netapp.com, bfields@fieldses.org, mingo@elte.hu, tony.luck@intel.com, mm-commits@vger.kernel.org The patch titled remove put_cpu_no_resched() has been removed from the -mm tree. Its filename was remove-put_cpu_no_resched.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: remove put_cpu_no_resched() From: Thomas Gleixner put_cpu_no_resched() is an optimization of put_cpu() which unfortunately can cause high latencies. The nfs iostats code uses put_cpu_no_resched() in a code sequence where a reschedule request caused by an interrupt between the get_cpu() and the put_cpu_no_resched() can delay the reschedule for at least HZ. The other users of put_cpu_no_resched() optimize correctly in interrupt code, but there is no real harm in using the put_cpu() function which is an alias for preempt_enable(). The extra check of the preemmpt count is not as critical as the potential source of missing a reschedule. Debugged in the preempt-rt tree and verified in mainline. Impact: remove a high latency source [akpm@linux-foundation.org: build fix] Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Cc: Tony Luck Cc: Trond Myklebust Cc: "J. Bruce Fields" Signed-off-by: Andrew Morton --- arch/ia64/kernel/perfmon.c | 2 +- fs/nfs/iostat.h | 6 +++--- include/linux/smp.h | 1 - 3 files changed, 4 insertions(+), 5 deletions(-) diff -puN arch/ia64/kernel/perfmon.c~remove-put_cpu_no_resched arch/ia64/kernel/perfmon.c --- a/arch/ia64/kernel/perfmon.c~remove-put_cpu_no_resched +++ a/arch/ia64/kernel/perfmon.c @@ -5595,7 +5595,7 @@ pfm_interrupt_handler(int irq, void *arg (*pfm_alt_intr_handler->handler)(irq, arg, regs); } - put_cpu_no_resched(); + put_cpu(); return IRQ_HANDLED; } diff -puN fs/nfs/iostat.h~remove-put_cpu_no_resched fs/nfs/iostat.h --- a/fs/nfs/iostat.h~remove-put_cpu_no_resched +++ a/fs/nfs/iostat.h @@ -31,7 +31,7 @@ static inline void nfs_inc_server_stats( cpu = get_cpu(); iostats = per_cpu_ptr(server->io_stats, cpu); iostats->events[stat]++; - put_cpu_no_resched(); + put_cpu(); } static inline void nfs_inc_stats(const struct inode *inode, @@ -50,7 +50,7 @@ static inline void nfs_add_server_stats( cpu = get_cpu(); iostats = per_cpu_ptr(server->io_stats, cpu); iostats->bytes[stat] += addend; - put_cpu_no_resched(); + put_cpu(); } static inline void nfs_add_stats(const struct inode *inode, @@ -71,7 +71,7 @@ static inline void nfs_add_fscache_stats cpu = get_cpu(); iostats = per_cpu_ptr(NFS_SERVER(inode)->io_stats, cpu); iostats->fscache[stat] += addend; - put_cpu_no_resched(); + put_cpu(); } #endif diff -puN include/linux/smp.h~remove-put_cpu_no_resched include/linux/smp.h --- a/include/linux/smp.h~remove-put_cpu_no_resched +++ a/include/linux/smp.h @@ -177,7 +177,6 @@ static inline void init_call_single_data #define get_cpu() ({ preempt_disable(); smp_processor_id(); }) #define put_cpu() preempt_enable() -#define put_cpu_no_resched() preempt_enable_no_resched() /* * Callback to arch code if there's nosmp or maxcpus=0 on the _ Patches currently in -mm which might be from tglx@linutronix.de are origin.patch linux-next.patch arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts.patch irqs-add-irqf_sample_random-to-the-feature-removal-scheduletxt-deprecated-list.patch ia64-remove-obsolete-no_irq_type.patch ia64-remove-obsolete-irq_desc_t-typedef.patch ia64-remove-obsolete-hw_interrupt_type.patch parisc-remove-obsolete-hw_interrupt_type.patch x86-fix-cpufreq-tsc-scaling.patch