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Message-Id: <20110425084508.dda5ec8f.randy.dunlap@oracle.com> Date: Mon, 25 Apr 2011 08:45:08 -0700 From: Randy Dunlap <randy.dunlap@...cle.com> To: Geunsik Lim <leemgs1@...il.com> Cc: Ingo Molnar <mingo@...e.hu>, Andrew Morton <akpm@...ux-foundation.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>, Steven Rostedt <rostedt@...dmis.org>, Darren Hart <dvhart@...ux.intel.com>, linux-kernel <linux-kernel@...r.kernel.org>, linux-rt-users <linux-rt-users@...r.kernel.org> Subject: Re: [PATCH 3/4] munmap: kbuild menu for munmap interface On Mon, 25 Apr 2011 19:44:31 +0900 Geunsik Lim wrote: > From: Geunsik Lim <geunsik.lim@...sung.com> > > Support kbuild menu to select memory unmap operation size > at build time. > > Signed-off-by: Geunsik Lim <geunsik.lim@...sung.com> > Acked-by: Hyunjin Choi <hj89.choi@...sung.com> > --- > init/Kconfig | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > mm/memory.c | 21 +++++++++++----- > 2 files changed, 84 insertions(+), 7 deletions(-) > > diff --git a/init/Kconfig b/init/Kconfig > index 56240e7..0983961 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -557,6 +557,76 @@ config LOG_BUF_SHIFT > 13 => 8 KB > 12 => 4 KB > > +config PREEMPT_OK_MUNMAP_RANGE > + int "Memory unmap unit on preemption mode (8 => 32KB)" > + depends on !PREEMPT_NONE > + range 8 2048 > + default 8 > + help > + unmap_vmas(=unmap a range of memory covered by a list of vma) is treading unmap_vmas (= unmap a range ... > + a delicate and uncomfortable line between hi-performance and low-latency. high performane and low latency. > + We've chosen to improve performance at the expense of latency. This option improves performance at the expense of latency. > + > + So although there may be no need to resched right now, reschedule > + if we keep on gathering more and more without flushing, gathering more and more <what> ? > + we'll be very unresponsive when a resched is needed later on. reschedule > + > + Consider the best suitable result between high performance and low latency > + on preemption mode. > + Select optimal munmap size to return memory space that is allocated by mmap system call. > + > + For example, For recording mass files, if we try to unmap memory that we allocated for > + with 100MB for recording in embedded devices, we have to wait for more than 3seconds to 3 seconds (but try not to put text over 80 columns, please) > + change mode from play mode to recording mode. This results from the unit of memory > + unmapped size when we are recording mass files like camcorder particularly. > + > + This value can be changed after boot using the > + /proc/sys/vm/munmap_unit_size tunable. Indent above with tab + 2 spaces. > + > + Examples: > + 2048 => 8,388,608bytes : for straight-line efficiency > + 1024 => 4,194,304bytes > + 512 => 2,097,152bytes > + 256 => 1,048,576bytes > + 128 => 524,288bytes > + 64 => 262,144bytes > + 32 => 131,072bytes > + 16 => 65,536bytes > + 8 => 32,768bytes : for low-latency (*default) All of above would be better with added space before "bytes", as, e.g.: 8 => 32,768 bytes > + > +config PREEMPT_NO_MUNMAP_RANGE > + int "Memory unmap unit on non-preemption mode (1024 => 4MB)" > + depends on PREEMPT_NONE > + range 8 2048 > + default 1024 > + help > + > + unmap_vmas(=unmap a range of memory covered by a list of vma) is treading unmap_vmas (= unmap > + a delicate and uncomfortable line between hi-performance and low-latency. high performance and low latency. > + We've chosen to improve performance at the expense of latency. This option improves performance at the expense of latency. > + > + So although there may be no need to resched right now, reschedule > + if we keep on gathering more and more without flushing, more and more what? > + we'll be very unresponsive when a resched is needed later on. reschedule > + > + Consider the best suitable result between high performance and low latency > + on preemption mode. but this option is for non-preempt mode... so should that text above be modified? > + Select optimal munmap size to return memory space that is allocated by mmap system call. > + > + This value can be changed after boot using the > + /proc/sys/vm/munmap_unit_size tunable. Indent above with tab + 2 spaces. > + > + Examples: > + 2048 => 8,388,608bytes : for straight-line efficiency > + 1024 => 4,194,304bytes (*default) > + 512 => 2,097,152bytes > + 256 => 1,048,576bytes > + 128 => 524,288bytes > + 64 => 262,144bytes > + 32 => 131,072bytes > + 16 => 65,536bytes > + 8 => 32,768bytes : for low-latency Use space before "bytes" in table above, please. > + > # > # Architectures with an unreliable sched_clock() should select this: > # --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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