summaryrefslogtreecommitdiff
path: root/kernel/up.c
AgeCommit message (Collapse)AuthorFilesLines
2017-08-29smp: Avoid using two cache lines for struct call_single_dataYing Huang1-1/+1
struct call_single_data is used in IPIs to transfer information between CPUs. Its size is bigger than sizeof(unsigned long) and less than cache line size. Currently it is not allocated with any explicit alignment requirements. This makes it possible for allocated call_single_data to cross two cache lines, which results in double the number of the cache lines that need to be transferred among CPUs. This can be fixed by requiring call_single_data to be aligned with the size of call_single_data. Currently the size of call_single_data is the power of 2. If we add new fields to call_single_data, we may need to add padding to make sure the size of new definition is the power of 2 as well. Fortunately, this is enforced by GCC, which will report bad sizes. To set alignment requirements of call_single_data to the size of call_single_data, a struct definition and a typedef is used. To test the effect of the patch, I used the vm-scalability multiple thread swap test case (swap-w-seq-mt). The test will create multiple threads and each thread will eat memory until all RAM and part of swap is used, so that huge number of IPIs are triggered when unmapping memory. In the test, the throughput of memory writing improves ~5% compared with misaligned call_single_data, because of faster IPIs. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Huang, Ying <ying.huang@intel.com> [ Add call_single_data_t and align with size of call_single_data. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Borislav Petkov <bp@suse.de> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Juergen Gross <jgross@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/87bmnqd6lz.fsf@yhuang-mobile.sh.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-05smp: Add function to execute a function synchronously on a CPUJuergen Gross1-0/+17
On some hardware models (e.g. Dell Studio 1555 laptop) some hardware related functions (e.g. SMIs) are to be executed on physical CPU 0 only. Instead of open coding such a functionality multiple times in the kernel add a service function for this purpose. This will enable the possibility to take special measures in virtualized environments like Xen, too. Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Douglas_Warzecha@dell.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akataria@vmware.com Cc: boris.ostrovsky@oracle.com Cc: chrisw@sous-sol.org Cc: david.vrabel@citrix.com Cc: hpa@zytor.com Cc: jdelvare@suse.com Cc: jeremy@goop.org Cc: linux@roeck-us.net Cc: pali.rohar@gmail.com Cc: rusty@rustcorp.com.au Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1472453327-19050-4-git-send-email-jgross@suse.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-05virt, sched: Add generic vCPU pinning supportJuergen Gross1-0/+1
Add generic virtualization support for pinning the current vCPU to a specified physical CPU. As this operation isn't performance critical (a very limited set of operations like BIOS calls and SMIs is expected to need this) just add a hypervisor specific indirection. Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Douglas_Warzecha@dell.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akataria@vmware.com Cc: boris.ostrovsky@oracle.com Cc: chrisw@sous-sol.org Cc: david.vrabel@citrix.com Cc: hpa@zytor.com Cc: jdelvare@suse.com Cc: jeremy@goop.org Cc: linux@roeck-us.net Cc: pali.rohar@gmail.com Cc: rusty@rustcorp.com.au Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1472453327-19050-3-git-send-email-jgross@suse.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-02-25smp: Rename __smp_call_function_single() to smp_call_function_single_async()Frederic Weisbecker1-2/+2
The name __smp_call_function_single() doesn't tell much about the properties of this function, especially when compared to smp_call_function_single(). The comments above the implementation are also misleading. The main point of this function is actually not to be able to embed the csd in an object. This is actually a requirement that result from the purpose of this function which is to raise an IPI asynchronously. As such it can be called with interrupts disabled. And this feature comes at the cost of the caller who then needs to serialize the IPIs on this csd. Lets rename the function and enhance the comments so that they reflect these properties. Suggested-by: Christoph Hellwig <hch@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@fb.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-02-25smp: Remove wait argument from __smp_call_function_single()Frederic Weisbecker1-2/+1
The main point of calling __smp_call_function_single() is to send an IPI in a pure asynchronous way. By embedding a csd in an object, a caller can send the IPI without waiting for a previous one to complete as is required by smp_call_function_single() for example. As such, sending this kind of IPI can be safe even when irqs are disabled. This flexibility comes at the expense of the caller who then needs to synchronize the csd lifecycle by himself and make sure that IPIs on a single csd are serialized. This is how __smp_call_function_single() works when wait = 0 and this usecase is relevant. Now there don't seem to be any usecase with wait = 1 that can't be covered by smp_call_function_single() instead, which is safer. Lets look at the two possible scenario: 1) The user calls __smp_call_function_single(wait = 1) on a csd embedded in an object. It looks like a nice and convenient pattern at the first sight because we can then retrieve the object from the IPI handler easily. But actually it is a waste of memory space in the object since the csd can be allocated from the stack by smp_call_function_single(wait = 1) and the object can be passed an the IPI argument. Besides that, embedding the csd in an object is more error prone because the caller must take care of the serialization of the IPIs for this csd. 2) The user calls __smp_call_function_single(wait = 1) on a csd that is allocated on the stack. It's ok but smp_call_function_single() can do it as well and it already takes care of the allocation on the stack. Again it's more simple and less error prone. Therefore, using the underscore prepend API version with wait = 1 is a bad pattern and a sign that the caller can do safer and more simple. There was a single user of that which has just been converted. So lets remove this option to discourage further users. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@fb.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-02-25smp: Teach __smp_call_function_single() to check for offline cpusJan Kara1-2/+3
Align __smp_call_function_single() with smp_call_function_single() so that it also checks whether requested cpu is still online. Signed-off-by: Jan Kara <jack@suse.cz> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jens Axboe <axboe@fb.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2013-11-15kernel: provide a __smp_call_function_single stub for !CONFIG_SMPChristoph Hellwig1-0/+11
Signed-off-by: Christoph Hellwig <hch@lst.de> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-12smp.h: move !SMP version of on_each_cpu() out-of-lineDavid Daney1-0/+11
All of the other non-trivial !SMP versions of functions in smp.h are out-of-line in up.c. Move on_each_cpu() there as well. This allows us to get rid of the #include <linux/irqflags.h>. The drawback is that this makes both the x86_64 and i386 defconfig !SMP kernels about 200 bytes larger each. Signed-off-by: David Daney <david.daney@cavium.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-12up.c: use local_irq_{save,restore}() in smp_call_function_single.David Daney1-3/+5
The SMP version of this function doesn't unconditionally enable irqs, so neither should this !SMP version. There are no know problems caused by this, but we make the change for consistency's sake. Signed-off-by: David Daney <david.daney@cavium.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-12smp: quit unconditionally enabling irq in on_each_cpu_mask and on_each_cpu_condDavid Daney1-0/+39
As in commit f21afc25f9ed ("smp.h: Use local_irq_{save,restore}() in !SMP version of on_each_cpu()"), we don't want to enable irqs if they are not already enabled. There are currently no known problematical callers of these functions, but since it is a known failure pattern, we preemptively fix them. Since they are not trivial functions, make them non-inline by moving them to up.c. This also makes it so we don't have to fix #include dependancies for preempt_{disable,enable}. Signed-off-by: David Daney <david.daney@cavium.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-10-31kernel: Map most files to use export.h instead of module.hPaul Gortmaker1-1/+1
The changed files were only including linux/module.h for the EXPORT_SYMBOL infrastructure, and nothing else. Revector them onto the isolated export header for faster compile times. Nothing to see here but a whole lot of instances of: -#include <linux/module.h> +#include <linux/export.h> This commit is only changing the kernel dir; next targets will probably be mm, fs, the arch dirs, etc. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2009-01-12smp_call_function_single(): be slightly less stupid, fix #2Ingo Molnar1-0/+1
fix m68k build failure: tip/kernel/up.c: In function 'smp_call_function_single': tip/kernel/up.c:16: error: dereferencing pointer to incomplete type make[2]: *** [kernel/up.o] Error 1 Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-11smp_call_function_single(): be slightly less stupid, fixIngo Molnar1-1/+3
Impact: build fix on Alpha kernel/up.c: In function 'smp_call_function_single': kernel/up.c:12: error: 'cpuid' undeclared (first use in this function) kernel/up.c:12: error: (Each undeclared identifier is reported only once kernel/up.c:12: error: for each function it appears in.) The typo didnt show up on x86 because 'cpuid' happens to be a function address as well ... Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-11smp_call_function_single(): be slightly less stupidAndrew Morton1-0/+18
If you do smp_call_function_single(expression-with-side-effects, ...) then expression-with-side-effects never gets evaluated on UP builds. As always, implementing it in C is the correct thing to do. While we're there, uninline it for size and possible header dependency reasons. And create a new kernel/up.c, as a place in which to put uniprocessor-specific code and storage. It should mirror kernel/smp.c. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>