From: Dave Hansen <dave.hansen@intel.com>
To: linux-ext4@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
"Theodore Ts'o" <tytso@mit.edu>, Jan kara <jack@suse.cz>
Subject: ext4 extent status tree LRU locking
Date: Tue, 11 Jun 2013 16:22:16 -0700 [thread overview]
Message-ID: <51B7B128.60909@intel.com> (raw)
I've got a test case which I intended to use to stress the VM a bit. It
fills memory up with page cache a couple of times. It essentially runs
30 or so cp's in parallel.
98% of my CPU is system time, and 96% of _that_ is being spent on the
spinlock in ext4_es_lru_add(). I think the LRU list head and its lock
end up being *REALLY* hot cachelines and are *the* bottleneck on this
test. Note that this is _before_ we go in to reclaim and actually start
calling in to the shrinker. There is zero memory pressure in this test.
I'm not sure the benefits of having a proper in-order LRU during reclaim
outweigh such a drastic downside for the common case.
Any thoughts?
next reply other threads:[~2013-06-11 23:22 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-11 23:22 Dave Hansen [this message]
2013-06-12 7:17 ` ext4 extent status tree LRU locking Zheng Liu
2013-06-12 15:09 ` Dave Hansen
2013-06-12 16:03 ` Zheng Liu
2013-06-12 17:52 ` Dave Hansen
2013-06-12 20:48 ` Theodore Ts'o
2013-06-13 13:27 ` Zheng Liu
2013-06-13 13:35 ` Theodore Ts'o
2013-06-14 3:27 ` Zheng Liu
2013-06-14 14:09 ` Zheng Liu
2013-06-14 14:02 ` Theodore Ts'o
2013-06-14 17:00 ` Zheng Liu
2013-06-14 18:00 ` Theodore Ts'o
2013-06-17 10:10 ` Zheng Liu
2013-06-17 21:12 ` Dave Hansen
2013-06-18 2:25 ` Zheng Liu
2013-06-18 2:51 ` Theodore Ts'o
2013-06-18 3:49 ` Zheng Liu
2013-06-18 2:47 ` Theodore Ts'o
2013-06-14 15:57 ` Dave Hansen
2013-06-14 17:11 ` Zheng Liu
2013-06-14 16:55 ` Dave Hansen
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