From 8b0b1db0133e4218a9b45c09e53793c039edebe1 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner <tglx@linutronix.de> Date: Tue, 16 Jun 2009 15:33:39 -0700 Subject: 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> --- fs/nfs/iostat.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs') diff --git a/fs/nfs/iostat.h b/fs/nfs/iostat.h index a2ab2529b5c..ceda50aad73 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 -- cgit v1.2.3-70-g09d2