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author | Tejun Heo <tj@kernel.org> | 2015-05-22 18:23:36 -0400 |
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committer | Jens Axboe <axboe@fb.com> | 2015-06-02 08:38:13 -0600 |
commit | 97c9341f727105c29478da19f1687b0e0a917256 (patch) | |
tree | ea533ba46133970f166b1dd280019a31516a10cd /include/uapi/xen | |
parent | c2aa723a6093633ae4ec15b08a4db276643cab3e (diff) | |
download | linux-97c9341f727105c29478da19f1687b0e0a917256.tar.gz linux-97c9341f727105c29478da19f1687b0e0a917256.tar.bz2 linux-97c9341f727105c29478da19f1687b0e0a917256.zip |
mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use
Because writeback wasn't cgroup aware before, the usual dirty
throttling mechanism in balance_dirty_pages() didn't work for
processes under memcg limit. The writeback path didn't know how much
memory is available or how fast the dirty pages are being written out
for a given memcg and balance_dirty_pages() didn't have any measure of
IO back pressure for the memcg.
To work around the issue, memcg implemented an ad-hoc dirty throttling
mechanism in the direct reclaim path by stalling on pages under
writeback which are encountered during direct reclaim scan. This is
rather ugly and crude - none of the configurability, fairness, or
bandwidth-proportional distribution of the normal path.
The previous patches implemented proper memcg aware dirty throttling
when cgroup writeback is in use making the ad-hoc mechanism
unnecessary. This patch disables direct reclaim stalling for such
case.
Note: I disabled the parts which seemed obvious and it behaves fine
while testing but my understanding of this code path is
rudimentary and it's quite possible that I got something wrong.
Please let me know if I got some wrong or more global_reclaim()
sites should be updated.
v2: The original patch removed the direct stalling mechanism which
breaks legacy hierarchies. Conditionalize instead of removing.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include/uapi/xen')
0 files changed, 0 insertions, 0 deletions