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448516e3f9
Implement a policy for the balloon device so that it starts taking
memory away from the VM when the system is under low memory conditions.
There are a few pieces here:
* Change the madvise call in MemoryMapping::dont_need_range to use
MADV_REMOVE instead of MADV_DONTNEED. The latter does nothing when
the memory mapping is shared across multiple processes while the
former immediately gives the pages in the specified range back to the
kernel. Subsequent accesses to memory in that range returns zero
pages.
* Change the protocol between the balloon device process and the main
crosvm process. Previously, the device process expected the main
process to send it increments in the amount of memory consumed by the
balloon device. Now, it instead just expects the absolute value of
the memory that should be consumed. To properly implement the policy
the main process needs to keep track of the total memory consumed by
the balloon device so this makes it easier to handle all the policy in
one place.
* Add a policy for dealing with low memory situations. When the VM
starts up, we determine the maximum amount of memory that the balloon
device should consume:
* If the VM has more than 1.5GB of memory, the balloon device max is
the size of the VM memory minus 1GB.
* Otherwise, if the VM has at least 500MB, the balloon device max is
50% of the size of the VM memory.
* Otherwise, the max is 0.
The increment used to change the size of the balloon is defined as
1/16 of the max memory that the balloon device will consume. When the
crosvm main process detects that the system is low on memory, it
immediately increases the balloon size by the increment (unless it has
already reached the max). It then starts 2 timers: one to check for
low memory conditions again in 1 seconds (+ jitter) and another to
check if the system is no longer low on memory in 1 minute (+ jitter)
with a subsequent interval of 30 seconds (+ jitter).
Under persistent low memory conditions the balloon device will consume
the maximum memory after 16 seconds. Once there is enough available
memory the balloon size will shrink back down to 0 after at most 9
minutes.
BUG=chromium:866193
TEST=manual
Start 2 VMs and write out a large file (size > system RAM) in each.
Observe /sys/kernel/mm/chromeos-low_mem/available and see that the
available memory steadily decreases until it goes under the low memory
margin at which point the available memory bounces back up as crosvm
frees up pages.
CQ-DEPEND=CL:1152214
Change-Id: I2046729683aa081c9d7ed039d902ad11737c1d52
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1149155
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
32 lines
751 B
Text
32 lines
751 B
Text
# Copyright 2017 The Chromium OS Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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close: 1
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exit_group: 1
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futex: 1
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# Disallow mmap with PROT_EXEC set. The syntax here doesn't allow bit
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# negation, thus the manually negated mask constant.
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mmap: arg2 in 0xfffffffb
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mprotect: arg2 in 0xfffffffb
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madvise: arg2 == MADV_DONTDUMP || arg2 == MADV_DONTNEED || arg2 == MADV_REMOVE
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munmap: 1
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read: 1
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recvfrom: 1
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sched_getaffinity: 1
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set_robust_list: 1
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sigaltstack: 1
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# Disallow clone's other than new threads.
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clone: arg0 & 0x00010000
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write: 1
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eventfd2: 1
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dup: 1
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poll: 1
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ppoll: 1
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getpid: 1
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# Allow PR_SET_NAME only.
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prctl: arg0 == 15
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epoll_create1: 1
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epoll_ctl: 1
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epoll_wait: 1
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