From: "Artem S. Tashkinov" <t.artem@lycos.com>
To: neilb@suse.de
Cc: david@lang.hm, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
axboe@kernel.dk, linux-mm@kvack.org
Subject: Re: Disabling in-memory write cache for x86-64 in Linux II
Date: Fri, 25 Oct 2013 21:03:44 +0000 (UTC) [thread overview]
Message-ID: <476525596.14731.1382735024280.JavaMail.mail@webmail11> (raw)
In-Reply-To: 20131026074349.0adc9646@notabene.brown
Oct 26, 2013 02:44:07 AM, neil wrote:
On Fri, 25 Oct 2013 18:26:23 +0000 (UTC) "Artem S. Tashkinov"
>>
>> Exactly. And not being able to use applications which show you IO performance
>> like Midnight Commander. You might prefer to use "cp -a" but I cannot imagine
>> my life without being able to see the progress of a copying operation. With the current
>> dirty cache there's no way to understand how you storage media actually behaves.
>
>So fix Midnight Commander. If you want the copy to be actually finished when
>it says it is finished, then it needs to call 'fsync()' at the end.
This sounds like a very bad joke. How applications are supposed to show and
calculate an _average_ write speed if there are no kernel calls/ioctls to actually
make the kernel flush dirty buffers _during_ copying? Actually it's a good way to
solve this problem in user space - alas, even if such calls are implemented, user
space will start using them only in 2018 if not further from that.
>>
>> Per device dirty cache seems like a nice idea, I, for one, would like to disable it
>> altogether or make it an absolute minimum for things like USB flash drives - because
>> I don't care about multithreaded performance or delayed allocation on such devices -
>> I'm interested in my data reaching my USB stick ASAP - because it's how most people
>> use them.
>>
>
>As has already been said, you can substantially disable the cache by tuning
>down various values in /proc/sys/vm/.
>Have you tried?
I don't understand who you are replying to. I asked about per device settings, you are
again referring me to system wide settings - they don't look that good if we're talking
about a 3MB/sec flash drive and 500MB/sec SSD drive. Besides it makes no sense
to allocate 20% of physical RAM for things which don't belong to it in the first place.
I don't know any other OS which has a similar behaviour.
And like people (including me) have already mentioned, such a huge dirty cache can
stall their PCs/servers for a considerable amount of time.
Of course, if you don't use Linux on the desktop you don't really care - well, I do. Also
not everyone in this world has an UPS - which means such a huge buffer can lead to a
serious data loss in case of a power blackout.
Regards,
Artem
next prev parent reply other threads:[~2013-10-25 21:03 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-25 7:25 Disabling in-memory write cache for x86-64 in Linux II Artem S. Tashkinov
2013-10-25 8:18 ` Linus Torvalds
2013-10-25 8:30 ` Artem S. Tashkinov
2013-10-25 8:43 ` Linus Torvalds
2013-10-25 9:15 ` Karl Kiniger
2013-10-29 20:30 ` Jan Kara
2013-10-29 20:43 ` Andrew Morton
2013-10-29 21:30 ` Jan Kara
2013-10-29 21:36 ` Linus Torvalds
2013-10-31 14:26 ` Karl Kiniger
2013-11-01 14:25 ` Maxim Patlasov
2013-11-01 14:31 ` [PATCH] mm: add strictlimit knob Maxim Patlasov
2013-11-04 22:01 ` Andrew Morton
2013-11-06 14:30 ` Maxim Patlasov
2013-11-06 15:05 ` [PATCH] mm: add strictlimit knob -v2 Maxim Patlasov
2013-11-07 12:26 ` Henrique de Moraes Holschuh
2013-11-22 23:45 ` Andrew Morton
2013-10-25 11:28 ` Disabling in-memory write cache for x86-64 in Linux II David Lang
2013-10-25 9:18 ` Theodore Ts'o
2013-10-25 9:29 ` Andrew Morton
2013-10-25 9:32 ` Linus Torvalds
2013-10-26 11:32 ` Pavel Machek
2013-10-26 20:03 ` Linus Torvalds
2013-10-29 20:57 ` Jan Kara
2013-10-29 21:33 ` Linus Torvalds
2013-10-29 22:13 ` Jan Kara
2013-10-29 22:42 ` Linus Torvalds
2013-11-01 17:22 ` Fengguang Wu
2013-11-04 12:19 ` Pavel Machek
2013-11-04 12:26 ` Pavel Machek
2013-10-30 12:01 ` Mel Gorman
2013-11-19 17:17 ` Rob Landley
2013-11-20 20:52 ` One Thousand Gnomes
2013-10-25 22:37 ` Fengguang Wu
2013-10-25 23:05 ` Fengguang Wu
2013-10-25 23:37 ` Theodore Ts'o
2013-10-29 20:40 ` Jan Kara
2013-10-30 10:07 ` Artem S. Tashkinov
2013-10-30 15:12 ` Jan Kara
2013-11-05 0:50 ` Andreas Dilger
2013-11-05 4:12 ` Dave Chinner
2013-11-07 13:48 ` Jan Kara
2013-11-11 3:22 ` Dave Chinner
2013-11-11 19:31 ` Jan Kara
2013-10-25 10:49 ` NeilBrown
2013-10-25 11:26 ` David Lang
2013-10-25 18:26 ` Artem S. Tashkinov
2013-10-25 19:40 ` Diego Calleja
2013-10-25 23:32 ` Fengguang Wu
2013-11-15 15:48 ` Diego Calleja
2013-10-25 20:43 ` NeilBrown
2013-10-25 21:03 ` Artem S. Tashkinov [this message]
2013-10-25 22:11 ` NeilBrown
[not found] ` <CAF7GXvpJVLYDS5NfH-NVuN9bOJjAS5c1MQqSTjoiVBHJt6bWcw@mail.gmail.com>
2013-11-05 1:47 ` David Lang
2013-11-05 2:08 ` NeilBrown
2013-10-29 20:49 ` Jan Kara
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