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| author | Thomas Gleixner <tglx@linutronix.de> | 2009-06-16 15:33:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-16 19:47:48 -0700 |
| commit | 8b0b1db0133e4218a9b45c09e53793c039edebe1 (patch) | |
| tree | 551ec8a69652b9856cefcf537bdcfd262f356974 | |
| parent | 10fc89d01a7ea2ecc2a58d2f4e7700f47178cd62 (diff) | |
| download | linux-8b0b1db0133e4218a9b45c09e53793c039edebe1.tar.gz | |
remove put_cpu_no_resched()
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 <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Tony Luck <tony.luck@intel.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: "J. Bruce Fields" <bfields@fieldses.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/ia64/kernel/perfmon.c | 2 | ||||
| -rw-r--r-- | fs/nfs/iostat.h | 6 | ||||
| -rw-r--r-- | include/linux/smp.h | 1 |
3 files changed, 4 insertions, 5 deletions
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c index 8a06dc480594..bdc176cb5e85 100644 --- a/arch/ia64/kernel/perfmon.c +++ b/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 --git a/fs/nfs/iostat.h b/fs/nfs/iostat.h index a2ab2529b5ca..ceda50aad73c 100644 --- a/fs/nfs/iostat.h +++ b/fs/nfs/iostat.h @@ -31,7 +31,7 @@ static inline void nfs_inc_server_stats(const struct nfs_server *server, 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(const struct nfs_server *server, 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(struct inode *inode, 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 --git a/include/linux/smp.h b/include/linux/smp.h index a69db820eed6..9e3d8af09207 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -177,7 +177,6 @@ static inline void init_call_single_data(void) #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 |