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From: Laurent Chavey <chavey@google.com>
To: linux-mm@kvack.org
Cc: LKML <linux-kernel@vger.kernel.org>,
	laurent chavey <chavey@google.com>,
	glommer@parallels.com
Subject: question: why use vzalloc() and vzfree() in mem_cgroup_alloc() and mem_cgroup_free()
Date: Wed, 14 Dec 2011 12:12:41 -0800	[thread overview]
Message-ID: <CAEas1LKNMSxhp-7DpsOOCu0fx6kx5ya-zqsZQgnf6JwzX0E0gw@mail.gmail.com> (raw)

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context:

While testing patches from Glauber Costa, "adding support
for tcp memory allocation in kmem cgroup", we hit a
BUG_ON(in_interrupt()) in vfree(). The code path in question
is taken because the izeof(struct mem_cgroup) is
>= PAGE_SIZE in the call to mem_cgroup_free(),

Since socket may get free in an interrupt context,
the combination of vzalloc(), vfree() should not be used
when accounting for socket mem (unless the code is modified).

question:

Is there reasons why vzalloc() is used in mem_cgroup_alloc() ?
    . are we seeing mem fragmentations to level that fail
      kzalloc() or kmalloc().
    . do we have empirical data that shows the allocation failure
      rate for kmalloc(), kzalloc() per alloc size (num pages)

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             reply	other threads:[~2011-12-14 20:13 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-14 20:12 Laurent Chavey [this message]
2011-12-15  0:52 ` Chris Snook

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