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Emulate illumos interface cv_timedwait_hires()

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Needed for Illumos #3582. This interface is supposed to support
a variable-resolution timeout with nanosecond granularity.  This
implementation rounds up to microsecond resolution, as nanosecond-
precision timing is rarely needed for real-world performance
tuning and may incur unnecessary busy-waiting.  usleep_range() is
used if available, otherwise udelay() or msleep() are used
depending on the length of the delay interval.

Add flags from sys/callo.h as these are used to control the behavior of
cv_timedwait_hires().  Specifically,

CALLOUT_FLAG_ABSOLUTE
    Normally, the expiration passed to the timeout API functions is
    an expiration interval. If this flag is specified, then it is
    interpreted as the expiration time itself.

CALLOUT_FLAG_ROUNDUP
    Roundup the expiration time to the next resolution boundary. If this
    flag is not specified, the expiration time is rounded down.

References:
    https://www.illumos.org/issues/3582
    illumos/illumos-gate@0689f76

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #304
This commit is contained in:
Ned Bass 2013-11-01 13:37:58 -07:00 committed by Brian Behlendorf
parent 0f4b9a5806
commit 184c687387
8 changed files with 212 additions and 0 deletions
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23
config/spl-build.m4
View File

@ -93,6 +93,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
SPL_AC_RWSEM_SPINLOCK_IS_RAW
SPL_AC_SCHED_RT_HEADER
SPL_AC_2ARGS_VFS_GETATTR
SPL_AC_USLEEP_RANGE
])
AC_DEFUN([SPL_AC_MODULE_SYMVERS], [
@ -2400,3 +2401,25 @@ AC_DEFUN([SPL_AC_2ARGS_VFS_GETATTR], [
])
])
])
dnl #
dnl # 2.6.36 API compatibility.
dnl # Added usleep_range timer.
dnl # usleep_range is a finer precision implementation of msleep
dnl # designed to be a drop-in replacement for udelay where a precise
dnl # sleep / busy-wait is unnecessary.
dnl #
AC_DEFUN([SPL_AC_USLEEP_RANGE], [
AC_MSG_CHECKING([whether usleep_range() is available])
SPL_LINUX_TRY_COMPILE([
#include <linux/delay.h>
],[
usleep_range(0, 0);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_USLEEP_RANGE, 1,
[usleep_range is available])
],[
AC_MSG_RESULT(no)
])
])

1
include/linux/Makefile.am
View File

@ -3,6 +3,7 @@ COMMON_H =
KERNEL_H = \
$(top_srcdir)/include/linux/bitops_compat.h \
$(top_srcdir)/include/linux/compiler_compat.h \
$(top_srcdir)/include/linux/delay_compat.h \
$(top_srcdir)/include/linux/file_compat.h \
$(top_srcdir)/include/linux/kallsyms_compat.h \
$(top_srcdir)/include/linux/list_compat.h \

47
include/linux/delay_compat.h Normal file
View File

@ -0,0 +1,47 @@
/*****************************************************************************\
* Copyright (C) 2007-2013 Lawrence Livermore National Security, LLC.
* Copyright (C) 2007 The Regents of the University of California.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
* For details, see <http://zfsonlinux.org/>.
*
* The SPL is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* The SPL is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
\*****************************************************************************/
#ifndef _SPL_DELAY_COMPAT_H
#define _SPL_DELAY_COMPAT_H
#include <linux/delay.h>
#include <linux/time.h>
/* usleep_range() introduced in 2.6.36 */
#ifndef HAVE_USLEEP_RANGE
static inline void
usleep_range(unsigned long min, unsigned long max)
{
unsigned int min_ms = min / USEC_PER_MSEC;
if (min >= MAX_UDELAY_MS)
msleep(min_ms);
else
udelay(min);
}
#endif /* HAVE_USLEEP_RANGE */
#endif /* _SPL_DELAY_COMPAT_H */

1
include/sys/Makefile.am
View File

@ -13,6 +13,7 @@ KERNEL_H = \
$(top_srcdir)/include/sys/buf.h \
$(top_srcdir)/include/sys/byteorder.h \
$(top_srcdir)/include/sys/callb.h \
$(top_srcdir)/include/sys/callo.h \
$(top_srcdir)/include/sys/cmn_err.h \
$(top_srcdir)/include/sys/compress.h \
$(top_srcdir)/include/sys/condvar.h \

52
include/sys/callo.h Normal file
View File

@ -0,0 +1,52 @@
/*****************************************************************************\
* Copyright (C) 2007-2013 Lawrence Livermore National Security, LLC.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
* For details, see <http://zfsonlinux.org/>.
*
* The SPL is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* The SPL is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
\*****************************************************************************/
#ifndef _SPL_CALLO_H
#define _SPL_CALLO_H
/*
* Callout flags:
*
* CALLOUT_FLAG_ROUNDUP
* Roundup the expiration time to the next resolution boundary.
* If this flag is not specified, the expiration time is rounded down.
* CALLOUT_FLAG_ABSOLUTE
* Normally, the expiration passed to the timeout API functions is an
* expiration interval. If this flag is specified, then it is
* interpreted as the expiration time itself.
* CALLOUT_FLAG_HRESTIME
* Normally, callouts are not affected by changes to system time
* (hrestime). This flag is used to create a callout that is affected
* by system time. If system time changes, these timers must be
* handled in a special way (see callout.c). These are used by condition
* variables and LWP timers that need this behavior.
* CALLOUT_FLAG_32BIT
* Legacy interfaces timeout() and realtime_timeout() pass this flag
* to timeout_generic() to indicate that a 32-bit ID should be allocated.
*/
#define CALLOUT_FLAG_ROUNDUP 0x1
#define CALLOUT_FLAG_ABSOLUTE 0x2
#define CALLOUT_FLAG_HRESTIME 0x4
#define CALLOUT_FLAG_32BIT 0x8
#endif /* _SPL_CALLB_H */

4
include/sys/condvar.h
View File

@ -27,8 +27,10 @@
#include <linux/module.h>
#include <linux/wait.h>
#include <linux/delay_compat.h>
#include <sys/kmem.h>
#include <sys/mutex.h>
#include <sys/callo.h>
/*
* The kcondvar_t struct is protected by mutex taken externally before
@ -56,6 +58,8 @@ extern void __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp);
extern clock_t __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time);
extern clock_t __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp,
clock_t exp_time);
extern clock_t cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp,
hrtime_t tim, hrtime_t res, int flag);
extern void __cv_signal(kcondvar_t *cvp);
extern void __cv_broadcast(kcondvar_t *cvp);

3
include/sys/time.h
View File

@ -47,6 +47,9 @@
#define MICROSEC 1000000
#define NANOSEC 1000000000
#define MSEC2NSEC(m) ((hrtime_t)(m) * (NANOSEC / MILLISEC))
#define NSEC2MSEC(n) ((n) / (NANOSEC / MILLISEC))
/* Already defined in include/linux/time.h */
#undef CLOCK_THREAD_CPUTIME_ID
#undef CLOCK_REALTIME

81
module/spl/spl-condvar.c
View File

@ -226,6 +226,87 @@ __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
}
EXPORT_SYMBOL(__cv_timedwait_interruptible);
/*
*'expire_time' argument is an absolute clock time in nanoseconds.
* Return value is time left (expire_time - now) or -1 if timeout occurred.
*/
static clock_t
__cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp,
hrtime_t expire_time, int state)
{
DEFINE_WAIT(wait);
hrtime_t time_left, now;
unsigned long time_left_us;
SENTRY;
ASSERT(cvp);
ASSERT(mp);
ASSERT(cvp->cv_magic == CV_MAGIC);
ASSERT(mutex_owned(mp));
atomic_inc(&cvp->cv_refs);
if (cvp->cv_mutex == NULL)
cvp->cv_mutex = mp;
/* Ensure the same mutex is used by all callers */
ASSERT(cvp->cv_mutex == mp);
now = gethrtime();
time_left = expire_time - now;
if (time_left <= 0) {
atomic_dec(&cvp->cv_refs);
SRETURN(-1);
}
time_left_us = time_left / NSEC_PER_USEC;
prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
atomic_inc(&cvp->cv_waiters);
/* Mutex should be dropped after prepare_to_wait() this
* ensures we're linked in to the waiters list and avoids the
* race where 'cvp->cv_waiters > 0' but the list is empty. */
mutex_exit(mp);
/* Allow a 100 us range to give kernel an opportunity to coalesce
* interrupts */
usleep_range(time_left_us, time_left_us + 100);
mutex_enter(mp);
/* No more waiters a different mutex could be used */
if (atomic_dec_and_test(&cvp->cv_waiters)) {
cvp->cv_mutex = NULL;
wake_up(&cvp->cv_destroy);
}
finish_wait(&cvp->cv_event, &wait);
atomic_dec(&cvp->cv_refs);
time_left = expire_time - gethrtime();
SRETURN(time_left > 0 ? time_left : -1);
}
/*
* Compatibility wrapper for the cv_timedwait_hires() Illumos interface.
*/
clock_t
cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp, hrtime_t tim,
hrtime_t res, int flag)
{
if (res > 1) {
/*
* Align expiration to the specified resolution.
*/
if (flag & CALLOUT_FLAG_ROUNDUP)
tim += res - 1;
tim = (tim / res) * res;
}
if (!(flag & CALLOUT_FLAG_ABSOLUTE))
tim += gethrtime();
return __cv_timedwait_hires(cvp, mp, tim, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(cv_timedwait_hires);
void
__cv_signal(kcondvar_t *cvp)
{