From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Neil Brown <neilb@suse.de>
Cc: Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>,
linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 004 of 11] md: Increase the delay before marking metadata clean, and make it configurable.
Date: Mon, 01 May 2006 16:15:00 +1000 [thread overview]
Message-ID: <4455A764.1000307@yahoo.com.au> (raw)
In-Reply-To: <17493.42109.153523.381980@cse.unsw.edu.au>
Neil Brown wrote:
>On Sunday April 30, akpm@osdl.org wrote:
>
>>NeilBrown <neilb@suse.de> wrote:
>>
>>>
>>>When a md array has been idle (no writes) for 20msecs it is marked as
>>>'clean'. This delay turns out to be too short for some real
>>>workloads. So increase it to 200msec (the time to update the metadata
>>>should be a tiny fraction of that) and make it sysfs-configurable.
>>>
>>>
>>>...
>>>
>>>+ safe_mode_delay
>>>+ When an md array has seen no write requests for a certain period
>>>+ of time, it will be marked as 'clean'. When another write
>>>+ request arrive, the array is marked as 'dirty' before the write
>>>+ commenses. This is known as 'safe_mode'.
>>>+ The 'certain period' is controlled by this file which stores the
>>>+ period as a number of seconds. The default is 200msec (0.200).
>>>+ Writing a value of 0 disables safemode.
>>>+
>>>
>>Why not make the units milliseconds? Rename this to safe_mode_delay_msecs
>>to remove any doubt.
>>
>
>Because umpteen years ago when I was adding thread-usage statistics to
>/proc/net/rpc/nfsd I used milliseconds and Linus asked me to make it
>seconds - a much more "obvious" unit. See Email below.
>It seems very sensible to me.
>
Either way, all ambiguity is removed if you put the unit in the name. And
don't use jiffies because that obviously is not portable (which sounds like
it was Linus' biggest concern).
Once you do that, I don't much care whether you use seconds or milliseconds.
Other than to note that many of our units now are ms, especially when
they're
measuring things at or around the ms order of magnitude. But I'm not
aware of
so many proc values that don't work in integers.
--
Send instant messages to your online friends http://au.messenger.yahoo.com
next prev parent reply other threads:[~2006-05-01 6:15 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-01 5:29 [PATCH 000 of 11] md: Introduction - assort md enhancements for 2.6.18 NeilBrown
2006-05-01 5:30 ` [PATCH 001 of 11] md: Reformat code in raid1_end_write_request to avoid goto NeilBrown
2006-05-01 5:30 ` [PATCH 002 of 11] md: Remove arbitrary limit on chunk size NeilBrown
2006-05-01 5:30 ` [PATCH 003 of 11] md: Remove useless ioctl warning NeilBrown
2006-05-01 5:30 ` [PATCH 004 of 11] md: Increase the delay before marking metadata clean, and make it configurable NeilBrown
2006-05-01 5:44 ` Andrew Morton
2006-05-01 6:02 ` Neil Brown
2006-05-01 6:13 ` Andrew Morton
2006-05-01 15:17 ` Linus Torvalds
2006-05-01 6:15 ` Nick Piggin [this message]
2006-05-02 5:56 ` bert hubert
2006-05-09 1:40 ` Neil Brown
2006-05-01 5:30 ` [PATCH 006 of 11] md: Remove nuisance message at shutdown NeilBrown
2006-05-01 5:30 ` [PATCH 007 of 11] md: Allow checkpoint of recovery with version-1 superblock NeilBrown
2006-05-01 5:30 ` [PATCH 008 of 11] md: Allow a linear array to have drives added while active NeilBrown
2006-05-01 5:30 ` [PATCH 009 of 11] md: Support stripe/offset mode in raid10 NeilBrown
2006-05-02 16:38 ` Al Boldi
2006-05-03 0:05 ` Neil Brown
2006-05-03 4:00 ` Al Boldi
2006-05-08 7:17 ` Neil Brown
2006-05-08 16:59 ` Al Boldi
2006-05-17 21:32 ` Raid5 resize "testing opportunity" Patrik Jonsson
2006-05-17 23:49 ` Neil Brown
2006-05-19 0:40 ` Patrik Jonsson
2006-05-19 0:44 ` Neil Brown
2006-05-19 20:11 ` Per Lindstrand
2006-05-01 5:31 ` [PATCH 010 of 11] md: make md_print_devices() static NeilBrown
2006-05-01 5:31 ` [PATCH 011 of 11] md: Split reshape portion of raid5 sync_request into a separate function NeilBrown
[not found] ` <1060501053025.22961@suse.de>
2006-05-01 5:40 ` [PATCH 005 of 11] md: Merge raid5 and raid6 code H. Peter Anvin
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