- 20 Dec, 2015 6 commits
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Darren Hart authored
While reviewing Michael Kerrisk's recent futex manpage update, I noticed that we allow the FUTEX_CLOCK_REALTIME flag for FUTEX_WAIT_BITSET but not for FUTEX_WAIT. FUTEX_WAIT is treated as a simple version for FUTEX_WAIT_BITSET internally (with a bitmask of FUTEX_BITSET_MATCH_ANY). As such, I cannot come up with a reason for this exclusion for FUTEX_WAIT. This change does modify the behavior of the futex syscall, changing a call with FUTEX_WAIT | FUTEX_CLOCK_REALTIME from returning -ENOSYS, to be equivalent to FUTEX_WAIT_BITSET | FUTEX_CLOCK_REALTIME with a bitset of FUTEX_BITSET_MATCH_ANY. Reported-by:
Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by:
Darren Hart <dvhart@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Link: http://lkml.kernel.org/r/9f3bdc116d79d23f5ee72ceb9a2a857f5ff8fa29.1450474525.git.dvhart@linux.intel.comSigned-off-by:
Thomas Gleixner <tglx@linutronix.de>
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Thomas Gleixner authored
out_unlock: does not only drop the locks, it also drops the refcount on the pi_state. Really intuitive. Move the label after the put_pi_state() call and use 'break' in the error handling path of the requeue loop. Signed-off-by:
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Thomas Gleixner authored
In the error handling cases we neither have pi_state nor a reference to it. Remove the pointless code. Signed-off-by:
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Thomas Gleixner authored
Documentation of the pi_state refcounting in the requeue code is non existent. Add it. Signed-off-by:
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Thomas Gleixner authored
free_pi_state() is confusing as it is in fact only freeing/caching the pi state when the last reference is gone. Rename it to put_pi_state() which reflects better what it is doing. Signed-off-by:
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Thomas Gleixner authored
If the proxy lock in the requeue loop acquires the rtmutex for a waiter then it acquired also refcount on the pi_state related to the futex, but the waiter side does not drop the reference count. Add the missing free_pi_state() call. Signed-off-by:
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- 04 Dec, 2015 15 commits
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Davidlohr Bueso authored
It serves no purpose but to confuse readers, and is most likely a left over from constant memory-barriers.txt updates. I.e.: http://lists.openwall.net/linux-kernel/2006/07/15/27Signed-off-by:
Davidlohr Bueso <dave@stgolabs.net> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <linux-arch@vger.kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1445975631-17047-5-git-send-email-dave@stgolabs.netSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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Davidlohr Bueso authored
With commit b92b8b35 ("locking/arch: Rename set_mb() to smp_store_mb()") it was made clear that the context of this call (and thus set_mb) is strictly for CPU ordering, as opposed to IO. As such all archs should use the smp variant of mb(), respecting the semantics and saving a mandatory barrier on UP. Signed-off-by:
Davidlohr Bueso <dbueso@suse.de> Signed-off-by:
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Davidlohr Bueso authored
It seems that commit 5dc12dde ("Remove tas()") missed some files. Correct this and fully drop this macro, for which we should be using cmpxchg() like calls. Signed-off-by:
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Waiman Long authored
In an overcommitted guest where some vCPUs have to be halted to make forward progress in other areas, it is highly likely that a vCPU later in the spinlock queue will be spinning while the ones earlier in the queue would have been halted. The spinning in the later vCPUs is then just a waste of precious CPU cycles because they are not going to get the lock soon as the earlier ones have to be woken up and take their turn to get the lock. This patch implements an adaptive spinning mechanism where the vCPU will call pv_wait() if the previous vCPU is not running. Linux kernel builds were run in KVM guest on an 8-socket, 4 cores/socket Westmere-EX system and a 4-socket, 8 cores/socket Haswell-EX system. Both systems are configured to have 32 physical CPUs. The kernel build times before and after the patch were: Westmere Haswell Patch 32 vCPUs 48 vCPUs 32 vCPUs 48 vCPUs ----- -------- -------- -------- -------- Before patch 3m02.3s 5m00.2s 1m43.7s 3m03.5s After patch 3m03.0s 4m37.5s 1m43.0s 2m47.2s For 32 vCPUs, this patch doesn't cause any noticeable change in performance. For 48 vCPUs (over-committed), there is about 8% performance improvement. Signed-off-by:
Waiman Long <Waiman.Long@hpe.com> Signed-off-by:
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Waiman Long authored
This patch allows one attempt for the lock waiter to steal the lock when entering the PV slowpath. To prevent lock starvation, the pending bit will be set by the queue head vCPU when it is in the active lock spinning loop to disable any lock stealing attempt. This helps to reduce the performance penalty caused by lock waiter preemption while not having much of the downsides of a real unfair lock. The pv_wait_head() function was renamed as pv_wait_head_or_lock() as it was modified to acquire the lock before returning. This is necessary because of possible lock stealing attempts from other tasks. Linux kernel builds were run in KVM guest on an 8-socket, 4 cores/socket Westmere-EX system and a 4-socket, 8 cores/socket Haswell-EX system. Both systems are configured to have 32 physical CPUs. The kernel build times before and after the patch were: Westmere Haswell Patch 32 vCPUs 48 vCPUs 32 vCPUs 48 vCPUs ----- -------- -------- -------- -------- Before patch 3m15.6s 10m56.1s 1m44.1s 5m29.1s After patch 3m02.3s 5m00.2s 1m43.7s 3m03.5s For the overcommited case (48 vCPUs), this patch is able to reduce kernel build time by more than 54% for Westmere and 44% for Haswell. Signed-off-by: -
Waiman Long authored
This patch enables the accumulation of kicking and waiting related PV qspinlock statistics when the new QUEUED_LOCK_STAT configuration option is selected. It also enables the collection of data which enable us to calculate the kicking and wakeup latencies which have a heavy dependency on the CPUs being used. The statistical counters are per-cpu variables to minimize the performance overhead in their updates. These counters are exported via the debugfs filesystem under the qlockstat directory. When the corresponding debugfs files are read, summation and computing of the required data are then performed. The measured latencies for different CPUs are: CPU Wakeup Kicking --- ------ ------- Haswell-EX 63.6us 7.4us Westmere-EX 67.6us 9.3us The measured latencies varied a bit from run-to-run. The wakeup latency is much higher than the kicking latency. A sample of statistical counters after system bootup (with vCPU overcommit) was: pv_hash_hops=1.00 pv_kick_unlock=1148 pv_kick_wake=1146 pv_latency_kick=11040 pv_latency_wake=194840 pv_spurious_wakeup=7 pv_wait_again=4 pv_wait_head=23 pv_wait_node=1129 Signed-off-by:
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Peter Zijlstra authored
These are some notes on the scheduler locking and how it provides program order guarantees on SMP systems. ( This commit is in the locking tree, because the new documentation refers to a newly introduced locking primitive. ) Signed-off-by:
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Peter Zijlstra authored
Introduce smp_cond_acquire() which combines a control dependency and a read barrier to form acquire semantics. This primitive has two benefits: - it documents control dependencies, - its typically cheaper than using smp_load_acquire() in a loop. Signed-off-by:
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Ingo Molnar authored
So we want to change a locking API, but the scheduler uses it, and a conflict is generated by a recent scheduler fix. Pick up the pending scheduler fixes to make life easier. Signed-off-by: -
Peter Zijlstra authored
Oleg noticed that its possible to falsely observe p->on_cpu == 0 such that we'll prematurely continue with the wakeup and effectively run p on two CPUs at the same time. Even though the overlap is very limited; the task is in the middle of being scheduled out; it could still result in corruption of the scheduler data structures. CPU0 CPU1 set_current_state(...) <preempt_schedule> context_switch(X, Y) prepare_lock_switch(Y) Y->on_cpu = 1; finish_lock_switch(X) store_release(X->on_cpu, 0); try_to_wake_up(X) LOCK(p->pi_lock); t = X->on_cpu; // 0 context_switch(Y, X) prepare_lock_switch(X) X->on_cpu = 1; finish_lock_switch(Y) store_release(Y->on_cpu, 0); </preempt_schedule> schedule(); deactivate_task(X); X->on_rq = 0; if (X->on_rq) // false if (t) while (X->on_cpu) cpu_relax(); context_switch(X, ..) finish_lock_switch(X) store_release(X->on_cpu, 0); Avoid the load of X->on_cpu being hoisted over the X->on_rq load. Reported-by:Oleg Nesterov <oleg@redhat.com> Signed-off-by:
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Peter Zijlstra authored
Explain how the control dependency and smp_rmb() end up providing ACQUIRE semantics and pair with smp_store_release() in finish_lock_switch(). Signed-off-by:
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Hiroshi Shimamoto authored
/proc/stats shows invalid gtime when the thread is running in guest. When vtime accounting is not enabled, we cannot get a valid delta. The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap is only updated when vtime accounting is runtime enabled. This patch makes task_gtime() just return gtime without computing the buggy non-existing tickless delta when vtime accounting is not enabled. Use context_tracking_is_enabled() to check if vtime is accounting on some cpu, in which case only we need to check the tickless delta. This way we fix the gtime value regression on machines not running nohz full. The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. I ran and stop a busy loop in VM and see the gtime in host. Dump the 43rd field which shows the gtime in every second: # while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep 1; done S 4348 R 7064566 R 7064766 R 7064967 R 7065168 S 4759 S 4759 During running busy loop, it returns large value. After applying this patch, we can see right gtime. # while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; sleep 1; done S 5338 R 5365 R 5465 R 5566 R 5666 S 5726 S 5726 Signed-off-by:Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by:
Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by:
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Xunlei Pang authored
root_domain::rto_mask allocated through alloc_cpumask_var() contains garbage data, this may cause problems. For instance, When doing pull_rt_task(), it may do useless iterations if rto_mask retains some extra garbage bits. Worse still, this violates the isolated domain rule for clustered scheduling using cpuset, because the tasks(with all the cpus allowed) belongs to one root domain can be pulled away into another root domain. The patch cleans the garbage by using zalloc_cpumask_var() instead of alloc_cpumask_var() for root_domain::rto_mask allocation, thereby addressing the issues. Do the same thing for root_domain's other cpumask memembers: dlo_mask, span, and online. Signed-off-by:
Xunlei Pang <xlpang@redhat.com> Signed-off-by:
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Sasha Levin authored
Because wakeups can (fundamentally) be late, a task might not be in the expected state. Therefore testing against a task's state is racy, and can yield false positives. Signed-off-by:
Sasha Levin <sasha.levin@oracle.com> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: oleg@redhat.com Fixes: 9067ac85 ("wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED task") Link: http://lkml.kernel.org/r/1448933660-23082-1-git-send-email-sasha.levin@oracle.comSigned-off-by:
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Peter Zijlstra authored
Vladimir reported getting RCU stall warnings and bisected it back to commit: 74316201 ("sched: Remove proliferation of wait_on_bit() action functions") That commit inadvertently reversed the calls to schedule() and signal_pending(), thereby not handling the case where the signal receives while we sleep. Reported-by:
Vladimir Murzin <vladimir.murzin@arm.com> Tested-by:
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- 23 Nov, 2015 7 commits
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Waiman Long authored
The unlock function in queued spinlocks was optimized for better performance on bare metal systems at the expense of virtualized guests. For x86-64 systems, the unlock call needs to go through a PV_CALLEE_SAVE_REGS_THUNK() which saves and restores 8 64-bit registers before calling the real __pv_queued_spin_unlock() function. The thunk code may also be in a separate cacheline from __pv_queued_spin_unlock(). This patch optimizes the PV unlock code path by: 1) Moving the unlock slowpath code from the fastpath into a separate __pv_queued_spin_unlock_slowpath() function to make the fastpath as simple as possible.. 2) For x86-64, hand-coded an assembly function to combine the register saving thunk code with the fastpath code. Only registers that are used in the fastpath will be saved and restored. If the fastpath fails, the slowpath function will be called via another PV_CALLEE_SAVE_REGS_THUNK(). For 32-bit, it falls back to the C __pv_queued_spin_unlock() code as the thunk saves and restores only one 32-bit register. With a microbenchmark of 5M lock-unlock loop, the table below shows the execution times before and after the patch with different number of threads in a VM running on a 32-core Westmere-EX box with x86-64 4.2-rc1 based kernels: Threads Before patch After patch % Change ------- ------------ ----------- -------- 1 134.1 ms 119.3 ms -11% 2 1286 ms 953 ms -26% 3 3715 ms 3480 ms -6.3% 4 4092 ms 3764 ms -8.0% Signed-off-by: -
Waiman Long authored
With optimistic prefetch of the next node cacheline, the next pointer may have been properly inititalized. As a result, the reading of node->next in the contended path may be redundant. This patch eliminates the redundant read if the next pointer value is not NULL. Signed-off-by:
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Waiman Long authored
A queue head CPU, after acquiring the lock, will have to notify the next CPU in the wait queue that it has became the new queue head. This involves loading a new cacheline from the MCS node of the next CPU. That operation can be expensive and add to the latency of locking operation. This patch addes code to optmistically prefetch the next MCS node cacheline if the next pointer is defined and it has been spinning for the MCS lock for a while. This reduces the locking latency and improves the system throughput. The performance change will depend on whether the prefetch overhead can be hidden within the latency of the lock spin loop. On really short critical section, there may not be performance gain at all. With longer critical section, however, it was found to have a performance boost of 5-10% over a range of different queue depths with a spinlock loop microbenchmark. Signed-off-by:
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Waiman Long authored
This patch replaces the cmpxchg() and xchg() calls in the native qspinlock code with the more relaxed _acquire or _release versions of those calls to enable other architectures to adopt queued spinlocks with less memory barrier performance overhead. Signed-off-by:
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Boqun Feng authored
Some atomic operations now have _relaxed/acquire/release variants, this patch adds some trivial tests for two purposes: 1. test the behavior of these new operations in single-CPU environment. 2. make their code generated before we actually use them somewhere, so that we can examine their assembly code. Signed-off-by:Boqun Feng <boqun.feng@gmail.com> Signed-off-by:
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Arnd Bergmann authored
The push_irq_work_func() function is conditionally defined only when both CONFIG_SMP and HAVE_RT_PUSH_IPI are defined, but the forward declaration remains visibile without HAVE_RT_PUSH_IPI, causing a gcc warning in ARM64 allnoconfig: kernel/sched/rt.c:68:13: warning: 'push_irq_work_func' declared 'static' but never defined [-Wunused-function] This changes the code to use the same condition for both the declaration and the function definition, which gets rid of the warning. As Peter Zijlstra, we can possibly get rid of the whole HAVE_RT_PUSH_IPI thing after: 8053871d ("smp: Fix smp_call_function_single_async() locking") Until that is done, this patch can be used to avoid the warning. Signed-off-by:
Arnd Bergmann <arnd@arndb.de> Signed-off-by:
Steven Rostedt <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: b6366f04 ("sched/rt: Use IPI to trigger RT task push migration instead of pulling") Link: http://lkml.kernel.org/r/3828565.oKfGk7yNIT@wuerfelSigned-off-by:
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Linus Torvalds authored
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- 22 Nov, 2015 12 commits
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Linus Torvalds authored
Merge slub bulk allocator updates from Andrew Morton: "This missed the merge window because I was waiting for some repairs to come in. Nothing actually uses the bulk allocator yet and the changes to other code paths are pretty small. And the net guys are waiting for this so they can start merging the client code" More comments from Jesper Dangaard Brouer: "The kmem_cache_alloc_bulk() call, in mm/slub.c, were included in previous kernel. The present version contains a bug. Vladimir Davydov noticed it contained a bug, when kernel is compiled with CONFIG_MEMCG_KMEM (see commit 03ec0ed5: "slub: fix kmem cgroup bug in kmem_cache_alloc_bulk"). Plus the mem cgroup counterpart in kmem_cache_free_bulk() were missing (see commit 03374518 "slub: add missing kmem cgroup support to kmem_cache_free_bulk"). I don't consider the fix stable-material because there are no in-tree users of the API. But with known bugs (for memcg) I cannot start using the API in the net-tree" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: slab/slub: adjust kmem_cache_alloc_bulk API slub: add missing kmem cgroup support to kmem_cache_free_bulk slub: fix kmem cgroup bug in kmem_cache_alloc_bulk slub: optimize bulk slowpath free by detached freelist slub: support for bulk free with SLUB freelists
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/ttyLinus Torvalds authored
Pull tty/serial fixes from Greg KH: "Here are a few small tty/serial driver fixes for 4.4-rc2 that resolve some reported problems. All have been in linux-next, full details are in the shortlog below" * tag 'tty-4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: serial: export fsl8250_handle_irq serial: 8250_mid: Add missing dependency tty: audit: Fix audit source serial: etraxfs-uart: Fix crash serial: fsl_lpuart: Fix earlycon support bcm63xx_uart: Use the device name when registering an interrupt tty: Fix direct use of tty buffer work tty: Fix tty_send_xchar() lock order inversion
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/stagingLinus Torvalds authored
Pull staging/IIO fixes from Greg KH: "Here are some staging and iio driver fixes for 4.4-rc2. All of these are in response to issues that have been reported and have been in linux-next for a while" * tag 'staging-4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging: Revert "Staging: wilc1000: coreconfigurator: Drop unneeded wrapper functions" iio: adc: xilinx: Fix VREFN scale iio: si7020: Swap data byte order iio: adc: vf610_adc: Fix division by zero error iio:ad7793: Fix ad7785 product ID iio: ad5064: Fix ad5629/ad5669 shift iio:ad5064: Make sure ad5064_i2c_write() returns 0 on success iio: lpc32xx_adc: fix warnings caused by enabling unprepared clock staging: iio: select IRQ_WORK for IIO_DUMMY_EVGEN vf610_adc: Fix internal temperature calculation
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usbLinus Torvalds authored
Pull USB fixes from Greg KH: "Here are a number of USB fixes and new device ids for 4.4-rc2. All have been in linux-next and the details are in the shortlog" * tag 'usb-4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (28 commits) usblp: do not set TASK_INTERRUPTIBLE before lock USB: MAINTAINERS: cxacru usb: kconfig: fix warning of select USB_OTG USB: option: add XS Stick W100-2 from 4G Systems xhci: Fix a race in usb2 LPM resume, blocking U3 for usb2 devices usb: xhci: fix checking ep busy for CFC xhci: Workaround to get Intel xHCI reset working more reliably usb: chipidea: imx: fix a possible NULL dereference usb: chipidea: usbmisc_imx: fix a possible NULL dereference usb: chipidea: otg: gadget module load and unload support usb: chipidea: debug: disable usb irq while role switch ARM: dts: imx27.dtsi: change the clock information for usb usb: chipidea: imx: refine clock operations to adapt for all platforms usb: gadget: atmel_usba_udc: Expose correct device speed usb: musb: enable usb_dma parameter usb: phy: phy-mxs-usb: fix a possible NULL dereference usb: dwc3: gadget: let us set lower max_speed usb: musb: fix tx fifo flush handling usb: gadget: f_loopback: fix the warning during the enumeration usb: dwc2: host: Fix remote wakeup when not in DWC2_L2 ...
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git://git.linux-mips.org/pub/scm/ralf/upstream-linusLinus Torvalds authored
Pull MIPS fixes from Ralf Baechle: - Fix a flood of annoying build warnings - A number of fixes for Atheros 79xx platforms * 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: MIPS: ath79: Add a machine entry for booting OF machines MIPS: ath79: Fix the size of the MISC INTC registers in ar9132.dtsi MIPS: ath79: Fix the DDR control initialization on ar71xx and ar934x MIPS: Fix flood of warnings about comparsion being always true.
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git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linuxLinus Torvalds authored
Pull parisc update from Helge Deller: "This patchset adds Huge Page and HUGETLBFS support for parisc" Honestly, the hugepage support should have gone through in the merge window, and is not really an rc-time fix. But it only touches arch/parisc, and I cannot find it in myself to care. If one of the three parisc users notices a breakage, I will point at Helge and make rude farting noises. * 'parisc-4.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux: parisc: Map kernel text and data on huge pages parisc: Add Huge Page and HUGETLBFS support parisc: Use long branch to do_syscall_trace_exit parisc: Increase initial kernel mapping to 32MB on 64bit kernel parisc: Initialize the fault vector earlier in the boot process. parisc: Add defines for Huge page support parisc: Drop unused MADV_xxxK_PAGES flags from asm/mman.h parisc: Drop definition of start_thread_som for HP-UX SOM binaries parisc: Fix wrong comment regarding first pmd entry flags
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipLinus Torvalds authored
Pull perf tool fixes from Thomas Gleixner: "A couple of fixes for perf tools: - Build system updates - Plug a memory leak in an error path of perf probe - Tear down probes correctly when adding fails - Fixes to the perf symbol handling - Fix ordering of event processing in buildid-list - Fix per DSO filtering in the histogram browser" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf probe: Clear probe_trace_event when add_probe_trace_event() fails perf probe: Fix memory leaking on failure by clearing all probe_trace_events perf inject: Also re-pipe lost_samples event perf buildid-list: Requires ordered events perf symbols: Fix dso lookup by long name and missing buildids perf symbols: Allow forcing reading of non-root owned files by root perf hists browser: The dso can be obtained from popup_action->ms.map->dso perf hists browser: Fix 'd' hotkey action to filter by DSO perf symbols: Rebuild rbtree when adjusting symbols for kcore tools: Add a "make all" rule tools: Actually install tmon in the install rule
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipLinus Torvalds authored
Pull x86 fixes from Thomas Gleixner: "This update contains: - MPX updates for handling 32bit processes - A fix for a long standing bug in 32bit signal frame handling related to FPU/XSAVE state - Handle get_xsave_addr() correctly in KVM - Fix SMAP check under paravirtualization - Add a comment to the static function trace entry to avoid further confusion about the difference to dynamic tracing" * 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/cpu: Fix SMAP check in PVOPS environments x86/ftrace: Add comment on static function tracing x86/fpu: Fix get_xsave_addr() behavior under virtualization x86/fpu: Fix 32-bit signal frame handling x86/mpx: Fix 32-bit address space calculation x86/mpx: Do proper get_user() when running 32-bit binaries on 64-bit kernels -
Jesper Dangaard Brouer authored
Adjust kmem_cache_alloc_bulk API before we have any real users. Adjust API to return type 'int' instead of previously type 'bool'. This is done to allow future extension of the bulk alloc API. A future extension could be to allow SLUB to stop at a page boundary, when specified by a flag, and then return the number of objects. The advantage of this approach, would make it easier to make bulk alloc run without local IRQs disabled. With an approach of cmpxchg "stealing" the entire c->freelist or page->freelist. To avoid overshooting we would stop processing at a slab-page boundary. Else we always end up returning some objects at the cost of another cmpxchg. To keep compatible with future users of this API linking against an older kernel when using the new flag, we need to return the number of allocated objects with this API change. Signed-off-by:
Jesper Dangaard Brouer <brouer@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Acked-by:
Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
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Jesper Dangaard Brouer authored
Initial implementation missed support for kmem cgroup support in kmem_cache_free_bulk() call, add this. If CONFIG_MEMCG_KMEM is not enabled, the compiler should be smart enough to not add any asm code. Incoming bulk free objects can belong to different kmem cgroups, and object free call can happen at a later point outside memcg context. Thus, we need to keep the orig kmem_cache, to correctly verify if a memcg object match against its "root_cache" (s->memcg_params.root_cache). Signed-off-by:
Vladimir Davydov <vdavydov@virtuozzo.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by:
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Jesper Dangaard Brouer authored
The call slab_pre_alloc_hook() interacts with kmemgc and is not allowed to be called several times inside the bulk alloc for loop, due to the call to memcg_kmem_get_cache(). This would result in hitting the VM_BUG_ON in __memcg_kmem_get_cache. As suggested by Vladimir Davydov, change slab_post_alloc_hook() to be able to handle an array of objects. A subtle detail is, loop iterator "i" in slab_post_alloc_hook() must have same type (size_t) as size argument. This helps the compiler to easier realize that it can remove the loop, when all debug statements inside loop evaluates to nothing. Note, this is only an issue because the kernel is compiled with GCC option: -fno-strict-overflow In slab_alloc_node() the compiler inlines and optimizes the invocation of slab_post_alloc_hook(s, flags, 1, &object) by removing the loop and access object directly. Signed-off-by:
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Jesper Dangaard Brouer authored
This change focus on improving the speed of object freeing in the "slowpath" of kmem_cache_free_bulk. The calls slab_free (fastpath) and __slab_free (slowpath) have been extended with support for bulk free, which amortize the overhead of the (locked) cmpxchg_double. To use the new bulking feature, we build what I call a detached freelist. The detached freelist takes advantage of three properties: 1) the free function call owns the object that is about to be freed, thus writing into this memory is synchronization-free. 2) many freelist's can co-exist side-by-side in the same slab-page each with a separate head pointer. 3) it is the visibility of the head pointer that needs synchronization. Given these properties, the brilliant part is that the detached freelist can be constructed without any need for synchronization. The freelist is constructed directly in the page objects, without any synchronization needed. The detached freelist is allocated on the stack of the function call kmem_cache_free_bulk. Thus, the freelist head pointer is not visible to other CPUs. All objects in a SLUB freelist must belong to the same slab-page. Thus, constructing the detached freelist is about matching objects that belong to the same slab-page. The bulk free array is scanned is a progressive manor with a limited look-ahead facility. Kmem debug support is handled in call of slab_free(). Notice kmem_cache_free_bulk no longer need to disable IRQs. This only slowed down single free bulk with approx 3 cycles. Performance data: Benchmarked[1] obj size 256 bytes on CPU i7-4790K @ 4.00GHz SLUB fastpath single object quick reuse: 47 cycles(tsc) 11.931 ns To get stable and comparable numbers, the kernel have been booted with "slab_merge" (this also improve performance for larger bulk sizes). Performance data, compared against fallback bulking: bulk - fallback bulk - improvement with this patch 1 - 62 cycles(tsc) 15.662 ns - 49 cycles(tsc) 12.407 ns- improved 21.0% 2 - 55 cycles(tsc) 13.935 ns - 30 cycles(tsc) 7.506 ns - improved 45.5% 3 - 53 cycles(tsc) 13.341 ns - 23 cycles(tsc) 5.865 ns - improved 56.6% 4 - 52 cycles(tsc) 13.081 ns - 20 cycles(tsc) 5.048 ns - improved 61.5% 8 - 50 cycles(tsc) 12.627 ns - 18 cycles(tsc) 4.659 ns - improved 64.0% 16 - 49 cycles(tsc) 12.412 ns - 17 cycles(tsc) 4.495 ns - improved 65.3% 30 - 49 cycles(tsc) 12.484 ns - 18 cycles(tsc) 4.533 ns - improved 63.3% 32 - 50 cycles(tsc) 12.627 ns - 18 cycles(tsc) 4.707 ns - improved 64.0% 34 - 96 cycles(tsc) 24.243 ns - 23 cycles(tsc) 5.976 ns - improved 76.0% 48 - 83 cycles(tsc) 20.818 ns - 21 cycles(tsc) 5.329 ns - improved 74.7% 64 - 74 cycles(tsc) 18.700 ns - 20 cycles(tsc) 5.127 ns - improved 73.0% 128 - 90 cycles(tsc) 22.734 ns - 27 cycles(tsc) 6.833 ns - improved 70.0% 158 - 99 cycles(tsc) 24.776 ns - 30 cycles(tsc) 7.583 ns - improved 69.7% 250 - 104 cycles(tsc) 26.089 ns - 37 cycles(tsc) 9.280 ns - improved 64.4% Performance data, compared current in-kernel bulking: bulk - curr in-kernel - improvement with this patch 1 - 46 cycles(tsc) - 49 cycles(tsc) - improved (cycles:-3) -6.5% 2 - 27 cycles(tsc) - 30 cycles(tsc) - improved (cycles:-3) -11.1% 3 - 21 cycles(tsc) - 23 cycles(tsc) - improved (cycles:-2) -9.5% 4 - 18 cycles(tsc) - 20 cycles(tsc) - improved (cycles:-2) -11.1% 8 - 17 cycles(tsc) - 18 cycles(tsc) - improved (cycles:-1) -5.9% 16 - 18 cycles(tsc) - 17 cycles(tsc) - improved (cycles: 1) 5.6% 30 - 18 cycles(tsc) - 18 cycles(tsc) - improved (cycles: 0) 0.0% 32 - 18 cycles(tsc) - 18 cycles(tsc) - improved (cycles: 0) 0.0% 34 - 78 cycles(tsc) - 23 cycles(tsc) - improved (cycles:55) 70.5% 48 - 60 cycles(tsc) - 21 cycles(tsc) - improved (cycles:39) 65.0% 64 - 49 cycles(tsc) - 20 cycles(tsc) - improved (cycles:29) 59.2% 128 - 69 cycles(tsc) - 27 cycles(tsc) - improved (cycles:42) 60.9% 158 - 79 cycles(tsc) - 30 cycles(tsc) - improved (cycles:49) 62.0% 250 - 86 cycles(tsc) - 37 cycles(tsc) - improved (cycles:49) 57.0% Performance with normal SLUB merging is significantly slower for larger bulking. This is believed to (primarily) be an effect of not having to share the per-CPU data-structures, as tuning per-CPU size can achieve similar performance. bulk - slab_nomerge - normal SLUB merge 1 - 49 cycles(tsc) - 49 cycles(tsc) - merge slower with cycles:0 2 - 30 cycles(tsc) - 30 cycles(tsc) - merge slower with cycles:0 3 - 23 cycles(tsc) - 23 cycles(tsc) - merge slower with cycles:0 4 - 20 cycles(tsc) - 20 cycles(tsc) - merge slower with cycles:0 8 - 18 cycles(tsc) - 18 cycles(tsc) - merge slower with cycles:0 16 - 17 cycles(tsc) - 17 cycles(tsc) - merge slower with cycles:0 30 - 18 cycles(tsc) - 23 cycles(tsc) - merge slower with cycles:5 32 - 18 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:4 34 - 23 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:-1 48 - 21 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:1 64 - 20 cycles(tsc) - 48 cycles(tsc) - merge slower with cycles:28 128 - 27 cycles(tsc) - 57 cycles(tsc) - merge slower with cycles:30 158 - 30 cycles(tsc) - 59 cycles(tsc) - merge slower with cycles:29 250 - 37 cycles(tsc) - 56 cycles(tsc) - merge slower with cycles:19 Joint work with Alexander Duyck. [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/slab_bulk_test01.c [akpm@linux-foundation.org: BUG_ON -> WARN_ON;return] Signed-off-by:Alexander Duyck <alexander.h.duyck@redhat.com> Acked-by:
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