kernel-ark/fs/nfs/iostat.h
Thomas Gleixner 8b0b1db013 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>
2009-06-16 19:47:48 -07:00

90 lines
1.9 KiB
C

/*
* linux/fs/nfs/iostat.h
*
* Declarations for NFS client per-mount statistics
*
* Copyright (C) 2005, 2006 Chuck Lever <cel@netapp.com>
*
*/
#ifndef _NFS_IOSTAT
#define _NFS_IOSTAT
#include <linux/percpu.h>
#include <linux/cache.h>
#include <linux/nfs_iostat.h>
struct nfs_iostats {
unsigned long long bytes[__NFSIOS_BYTESMAX];
#ifdef CONFIG_NFS_FSCACHE
unsigned long long fscache[__NFSIOS_FSCACHEMAX];
#endif
unsigned long events[__NFSIOS_COUNTSMAX];
} ____cacheline_aligned;
static inline void nfs_inc_server_stats(const struct nfs_server *server,
enum nfs_stat_eventcounters stat)
{
struct nfs_iostats *iostats;
int cpu;
cpu = get_cpu();
iostats = per_cpu_ptr(server->io_stats, cpu);
iostats->events[stat]++;
put_cpu();
}
static inline void nfs_inc_stats(const struct inode *inode,
enum nfs_stat_eventcounters stat)
{
nfs_inc_server_stats(NFS_SERVER(inode), stat);
}
static inline void nfs_add_server_stats(const struct nfs_server *server,
enum nfs_stat_bytecounters stat,
unsigned long addend)
{
struct nfs_iostats *iostats;
int cpu;
cpu = get_cpu();
iostats = per_cpu_ptr(server->io_stats, cpu);
iostats->bytes[stat] += addend;
put_cpu();
}
static inline void nfs_add_stats(const struct inode *inode,
enum nfs_stat_bytecounters stat,
unsigned long addend)
{
nfs_add_server_stats(NFS_SERVER(inode), stat, addend);
}
#ifdef CONFIG_NFS_FSCACHE
static inline void nfs_add_fscache_stats(struct inode *inode,
enum nfs_stat_fscachecounters stat,
unsigned long addend)
{
struct nfs_iostats *iostats;
int cpu;
cpu = get_cpu();
iostats = per_cpu_ptr(NFS_SERVER(inode)->io_stats, cpu);
iostats->fscache[stat] += addend;
put_cpu();
}
#endif
static inline struct nfs_iostats *nfs_alloc_iostats(void)
{
return alloc_percpu(struct nfs_iostats);
}
static inline void nfs_free_iostats(struct nfs_iostats *stats)
{
if (stats != NULL)
free_percpu(stats);
}
#endif /* _NFS_IOSTAT */