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Date: Tue, 26 Apr 2011 09:42:32 +0900 From: Geunsik Lim <leemgs1@...il.com> To: Randy Dunlap <randy.dunlap@...cle.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 Tue, Apr 26, 2011 at 12:45 AM, Randy Dunlap <randy.dunlap@...cle.com> wrote: > 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 *** Randy Dunlap. Thanks a lot. I will modify contents that you commented. > -- Regards, Geunsik Lim ( Samsung Electronics ) Blog : http://blog.naver.com/invain/ e-Mail: geunsik.lim@...sung.com leemgs@...il.com , leemgs1@...il.com -- 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/ -- 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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