The for loop in rcutorture_init uses the condition
cur_ops = torture_ops[i], cur_ops
but then makes the same assignment to cur_ops inside the loop. Remove the
redundant assignment inside the loop, and remove now-unnecessary braces.
Signed-off-by: Josh Triplett <josh@kernel.org>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Make TASK_PREEMPTS_CURR(task, rq) return "true" only if the task's prio
is higher than the current's one and the task is in the "active" array.
This ensures we don't make redundant resched_task() calls when the task
is in the "expired" array (as may happen now in set_user_prio(),
rt_mutex_setprio() and pull_task() ) ;
- generalise conditions for a call to resched_task() in set_user_nice(),
rt_mutex_setprio() and sched_setscheduler()
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a logical cpu 'x' already has more than one process running, then most
likely the siblings of that cpu 'x' must be busy. Otherwise the idle
siblings would have likely(in most of the scenarios) picked up the extra
load making the load on 'x' atmost one.
Use this logic to eliminate the siblings status check and minimize the cache
misses encountered on a heavily loaded system.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I noticed expensive divides done in try_to_wakeup() and
find_busiest_group() on a bi dual core Opteron machine (total of 4 cores),
moderatly loaded (15.000 context switch per second)
oprofile numbers :
CPU: AMD64 processors, speed 2600.05 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Cycles outside of halt state) with a unit
mask of 0x00 (No unit mask) count 50000
samples % symbol name
...
613914 1.0498 try_to_wake_up
834 0.0013 :ffffffff80227ae1: div %rcx
77513 0.1191 :ffffffff80227ae4: mov %rax,%r11
608893 1.0413 find_busiest_group
1841 0.0031 :ffffffff802260bf: div %rdi
140109 0.2394 :ffffffff802260c2: test %sil,%sil
Some of these divides can use the reciprocal divides we introduced some
time ago (currently used in slab AFAIK)
We can assume a load will fit in a 32bits number, because with a
SCHED_LOAD_SCALE=128 value, its still a theorical limit of 33554432
When/if we reach this limit one day, probably cpus will have a fast
hardware divide and we can zap the reciprocal divide trick.
Ingo suggested to rename cpu_power to __cpu_power to make clear it should
not be modified without changing its reciprocal value too.
I did not convert the divide in cpu_avg_load_per_task(), because tracking
nr_running changes may be not worth it ? We could use a static table of 32
reciprocal values but it would add a conditional branch and table lookup.
[akpm@linux-foundation.org: !SMP build fix]
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix the process idle load balancing in the presence of dynticks. cpus for
which ticks are stopped will sleep till the next event wakes it up.
Potentially these sleeps can be for large durations and during which today,
there is no periodic idle load balancing being done.
This patch nominates an owner among the idle cpus, which does the idle load
balancing on behalf of the other idle cpus. And once all the cpus are
completely idle, then we can stop this idle load balancing too. Checks added
in fast path are minimized. Whenever there are busy cpus in the system, there
will be an owner(idle cpu) doing the system wide idle load balancing.
Open items:
1. Intelligent owner selection (like an idle core in a busy package).
2. Merge with rcu's nohz_cpu_mask?
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Periodic load balancing in recent kernels happen in the softirq. In
certain -rt configurations, these softirqs are handled in softirqd context.
And hence the check for idle processor was always returning busy (as
nr_running > 1).
This patch captures the idle information at the tick and passes this info
to softirq context through an element 'idle_at_tick' in rq.
[kernel@kolivas.org: Fix reverse idle at tick logic]
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix incorrect spinlock use in hysdn_log_close(). The function declared a
spinlock on the stack and used it to 'protect' a shared driver structure.
The patch simply removes the useless code.
Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Cc: Karsten Keil <kkeil@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch makes it so that simple_fill_super and get_sb_pseudo assign their
root inodes to be number 1. It also fixes up a couple of callers of
simple_fill_super that were passing in files arrays that had an index at
number 1, and adds a warning for any caller that sends in such an array.
It would have been nice to have made it so that it wasn't possible to make
such a collision, but some callers need to be able to control what inode
number their entries get, so I think this is the best that can be done.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The problems are:
- on filesystems w/o permanent inode numbers, i_ino values can be larger
than 32 bits, which can cause problems for some 32 bit userspace programs on
a 64 bit kernel. We can't do anything for filesystems that have actual
>32-bit inode numbers, but on filesystems that generate i_ino values on the
fly, we should try to have them fit in 32 bits. We could trivially fix this
by making the static counters in new_inode and iunique 32 bits, but...
- many filesystems call new_inode and assume that the i_ino values they are
given are unique. They are not guaranteed to be so, since the static
counter can wrap. This problem is exacerbated by the fix for #1.
- after allocating a new inode, some filesystems call iunique to try to get
a unique i_ino value, but they don't actually add their inodes to the
hashtable, and so they're still not guaranteed to be unique if that counter
wraps.
This patch set takes the simpler approach of simply using iunique and hashing
the inodes afterward. Christoph H. previously mentioned that he thought that
this approach may slow down lookups for filesystems that currently hash their
inodes.
The questions are:
1) how much would this slow down lookups for these filesystems?
2) is it enough to justify adding more infrastructure to avoid it?
What might be best is to start with this approach and then only move to using
IDR or some other scheme if these extra inodes in the hashtable prove to be
problematic.
I've done some cursory testing with this patch and the overhead of hashing and
unhashing the inodes with pipefs is pretty low -- just a few seconds of system
time added on to the creation and destruction of 10 million pipes (very
similar to the overhead that the IDR approach would add).
The hard thing to measure is what effect this has on other filesystems. I'm
open to ways to try and gauge this.
Again, I've only converted pipefs as an example. If this approach is
acceptable then I'll start work on patches to convert other filesystems.
With a pretty-much-worst-case microbenchmark provided by Eric Dumazet
<dada1@cosmosbay.com>:
hashing patch (pipebench):
sys 1m15.329s
sys 1m16.249s
sys 1m17.169s
unpatched (pipebench):
sys 1m9.836s
sys 1m12.541s
sys 1m14.153s
Which works out to 1.05642174294555027017. So ~5-6% slowdown.
This patch:
When a 32-bit program that was not compiled with large file offsets does a
stat and gets a st_ino value back that won't fit in the 32 bit field, glibc
(correctly) generates an EOVERFLOW error. We can't do anything about fs's
with larger permanent inode numbers, but when we generate them on the fly, we
ought to try and have them fit within a 32 bit field.
This patch takes the first step toward this by making the static counters in
these two functions be 32 bits.
[jlayton@redhat.com: mention that it's only the case for 32bit, non-LFS stat]
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Here is a driver for the Alchemy au1550 PSC (Programmable Serial
Controller) in SPI master mode.
It supports dma transfers using the Alchemy descriptor based dma controller
for 4-8 bits per word SPI transfers. For 9-24 bits per word transfers, pio
irq based mode is used to avoid setup of dma channels from scratch on each
number of bits per word change.
Tested with au1550; this may also work on other MIPS Alchemy cpus, like
au1200/au1210/au1250. Used extensively with SD card connected via SPI;
this handles 8.1MHz SPI clock transfers using dma without any problem (the
highest SPI clock freq possible with au1550 running on 324MHz).
The driver supports sharing of SPI bus by multiple devices. All features
of Alchemy SPI mode are supported (all SPI modes, msb/lsb first, bits per
word in 4-24 range).
As the SPI clock of the controller depends on main input clock that shall
be configured externally, platform data structure for au1550 SPI controller
driver contains mainclk_hz attribute to define the input clock rate. From
this value, dividers of the controller for SPI clock are set up for
required frequency.
Signed-off-by: Jan Nikitenko <jan.nikitenko@gmail.com>
Whitespace and section fixups. Remove partial workaround for platform
setup bug in dma_mask setup; it couldn't work with multiple controllers.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Various documentation updates for the SPI infrastructure, to clarify things
that may not have been clear, to cope with lack of editing, and fix
omissions.
Also, plug SPI into the kernel-api DocBook template, and fix all the
resulting glitches in document generation.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a filesystem API for <linux/spi/spi.h> stack. The initial version of
this interface is purely synchronous.
dbrownell@users.sourceforge.net:
Cleaned up, bugfixed; much simplified; added preliminary documentation.
Works with mdev given CONFIG_SYSFS_DEPRECATED; and presumably udev.
Updated SPI_IOC_MESSAGE ioctl to full spi_message semantics, supporting
groups of one or more transfers (each of which may be full duplex if
desired).
This is marked as EXPERIMENTAL with an explicit disclaimer that the API
(notably the ioctls) is subject to change.
Signed-off-by: Andrea Paterniani <a.paterniani@swapp-eng.it>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Simplify the spi_butterfly driver by removing incomplete/unused support for
the second SPI bus, implemented by the USI controller. This should make
this a clearer example of how to write a parport bitbang driver.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Josh Triplett
Ahmed S. Darwish
Siddha, Suresh B
Dmitry Adamushko
Eric Dumazet
Thomas Gleixner
Matthias Kaehlcke
Mike Frysinger
Armin Schindler
Adrian Bunk
Jeff Layton
Jan Nikitenko
David Brownell
Andrea Paterniani
Josh Boyer