From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Chris Metcalf <cmetcalf@tilera.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
Gilad Ben-Yossef <gilad@benyossef.com>,
linux-kernel@vger.kernel.org, Christoph Lameter <cl@linux.com>,
linux-mm@kvack.org, Pekka Enberg <penberg@kernel.org>,
Matt Mackall <mpm@selenic.com>,
Sasha Levin <levinsasha928@gmail.com>,
Rik van Riel <riel@redhat.com>, Andi Kleen <andi@firstfloor.org>,
Mel Gorman <mel@csn.ul.ie>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Avi Kivity <avi@redhat.com>,
Michal Nazarewicz <mina86@mina86.com>,
Kosaki Motohiro <kosaki.motohiro@gmail.com>,
Milton Miller <miltonm@bga.com>
Subject: Re: [v7 0/8] Reduce cross CPU IPI interference
Date: Fri, 10 Feb 2012 19:38:25 +0100 [thread overview]
Message-ID: <1328899105.25989.37.camel@laptop> (raw)
In-Reply-To: <4F2AAEB9.9070302@tilera.com>
On Thu, 2012-02-02 at 10:41 -0500, Chris Metcalf wrote:
>
> /*
> * Quiesce the timer interrupt before returning to user space after a
> * system call. Normally if a task on a dataplane core makes a
> * syscall, the system will run one or more timer ticks after the
> * syscall has completed, causing unexpected interrupts in userspace.
> * Setting DP_QUIESCE avoids that problem by having the kernel "hold"
> * the task in kernel mode until the timer ticks are complete. This
> * will make syscalls dramatically slower.
> *
> * If multiple dataplane tasks are scheduled on a single core, this
> * in effect silently disables DP_QUIESCE, which allows the tasks to make
> * progress, but without actually disabling the timer tick.
> */
> #define DP_QUIESCE 0x1
This is what Frederics work does
>
> /*
> * Disallow the application from entering the kernel in any way,
> * unless it calls set_dataplane() again without this bit set.
> * Issuing any other syscall or causing a page fault would generate a
> * kernel message, and "kill -9" the process.
> *
> * Setting this flag automatically sets DP_QUIESCE as well.
> */
> #define DP_STRICT 0x2
This is a debug feature.. you'd better know what your own software does.
>
> /*
> * Debug dataplane interrupts, so that if any interrupt source
> * attempts to involve a dataplane cpu, a kernel message and stack
> * backtrace will be generated on the console. As this warning is a
> * slow event, it may make sense to avoid this mode in production code
> * to avoid making any possible interrupts even more heavyweight.
> *
> * Setting this flag automatically sets DP_QUIESCE as well.
> */
> #define DP_DEBUG 0x4
This too is a debug feature, one that doesn't cover all possible
scenarios.
> /*
> * Cause all memory mappings to be populated in the page table.
> * Specifying this when entering dataplane mode ensures that no future
> * page fault events will occur to cause interrupts into the Linux
> * kernel, as long as no new mappings are installed by mmap(), etc.
> * Note that since the hardware TLB is of finite size, there will
> * still be the potential for TLB misses that the hypervisor handles,
> * either via its software TLB cache (fast path) or by walking the
> * kernel page tables (slow path), so touching large amounts of memory
> * will still incur hypervisor interrupt overhead.
> */
> #define DP_POPULATE 0x8
map()s MAP_POPULATE will pre-populate the stuff for you, as will
mlock(), the latter will (mostly) ensure they stay around.
next prev parent reply other threads:[~2012-02-10 18:38 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-26 10:01 [v7 0/8] Reduce cross CPU IPI interference Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 1/8] smp: introduce a generic on_each_cpu_mask function Gilad Ben-Yossef
2012-01-29 12:24 ` Gilad Ben-Yossef
2012-01-30 21:52 ` Andrew Morton
2012-01-31 6:33 ` Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 2/8] arm: move arm over to generic on_each_cpu_mask Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 3/8] tile: move tile to use " Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 4/8] smp: add func to IPI cpus based on parameter func Gilad Ben-Yossef
2012-01-27 23:57 ` Andrew Morton
2012-01-29 12:04 ` Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 5/8] slub: only IPI CPUs that have per cpu obj to flush Gilad Ben-Yossef
2012-01-26 15:09 ` Christoph Lameter
2012-01-26 10:01 ` [v7 6/8] fs: only send IPI to invalidate LRU BH when needed Gilad Ben-Yossef
2012-01-26 10:02 ` [v7 7/8] mm: only IPI CPUs to drain local pages if they exist Gilad Ben-Yossef
2012-01-26 15:13 ` Christoph Lameter
2012-01-28 0:12 ` Andrew Morton
2012-01-29 12:18 ` Gilad Ben-Yossef
2012-01-30 21:49 ` Andrew Morton
2012-01-31 6:32 ` Gilad Ben-Yossef
2012-01-30 14:59 ` Mel Gorman
2012-01-30 15:14 ` Gilad Ben-Yossef
2012-01-30 15:44 ` Mel Gorman
2012-01-26 10:02 ` [v7 8/8] mm: add vmstat counters for tracking PCP drains Gilad Ben-Yossef
2012-01-26 15:19 ` [v7 0/8] Reduce cross CPU IPI interference Peter Zijlstra
2012-01-29 8:25 ` Gilad Ben-Yossef
2012-02-01 17:04 ` Frederic Weisbecker
2012-02-02 8:46 ` Gilad Ben-Yossef
2012-02-02 15:41 ` Chris Metcalf
2012-02-05 11:46 ` Gilad Ben-Yossef
2012-02-10 18:39 ` Peter Zijlstra
2012-02-10 20:13 ` Gilad Ben-Yossef
2012-02-10 20:29 ` Peter Zijlstra
2012-02-10 20:39 ` Gilad Ben-Yossef
2012-02-10 18:33 ` Peter Zijlstra
2012-02-10 20:33 ` Gilad Ben-Yossef
2012-02-15 21:50 ` Chris Metcalf
2012-02-15 22:15 ` Christoph Lameter
2012-02-15 23:44 ` Chris Metcalf
2012-02-21 1:34 ` Frederic Weisbecker
2012-03-01 18:27 ` Chris Metcalf
2012-02-10 18:38 ` Peter Zijlstra [this message]
2012-02-10 20:24 ` Gilad Ben-Yossef
2012-02-15 15:11 ` Peter Zijlstra
2012-02-15 15:19 ` Gilad Ben-Yossef
2012-02-15 21:51 ` Chris Metcalf
2012-02-02 16:24 ` Frederic Weisbecker
2012-02-02 16:29 ` Christoph Lameter
2012-02-09 15:52 ` Frederic Weisbecker
2012-02-09 15:59 ` Chris Metcalf
2012-02-09 18:11 ` Frederic Weisbecker
2012-02-09 16:26 ` Christoph Lameter
2012-02-09 18:32 ` Frederic Weisbecker
2012-02-01 17:35 ` Peter Zijlstra
2012-02-01 17:57 ` Peter Zijlstra
2012-02-02 9:42 ` Gilad Ben-Yossef
2012-02-01 18:40 ` Paul E. McKenney
2012-02-01 20:06 ` Christoph Lameter
2012-02-01 20:13 ` Paul E. McKenney
2012-02-02 9:34 ` Avi Kivity
2012-02-02 15:34 ` Paul E. McKenney
2012-02-02 16:14 ` Avi Kivity
2012-02-02 17:01 ` Paul E. McKenney
2012-02-02 17:23 ` Avi Kivity
2012-02-02 17:51 ` Paul E. McKenney
2012-02-05 12:16 ` Avi Kivity
2012-02-05 16:59 ` Paul E. McKenney
2012-02-09 15:22 ` Frederic Weisbecker
2012-02-09 16:05 ` Avi Kivity
2012-02-09 18:22 ` Frederic Weisbecker
2012-02-09 23:41 ` Paul E. McKenney
2012-02-10 1:39 ` Frederic Weisbecker
2012-02-14 13:18 ` Avi Kivity
2012-02-21 0:02 ` Frederic Weisbecker
2012-02-02 17:25 ` Christoph Lameter
2012-02-05 12:06 ` Gilad Ben-Yossef
2012-02-06 18:19 ` Christoph Lameter
2012-02-09 15:37 ` Frederic Weisbecker
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