diff options
| author | Rik van Riel <riel@redhat.com> | 2011-09-01 15:26:50 -0400 |
|---|---|---|
| committer | Colin Cross <ccross@android.com> | 2014-03-19 13:10:25 -0700 |
| commit | 526cbfac1562fcb58ef705b935f910c6664688f9 (patch) | |
| tree | 4ad782440baf4a7ee3694da4542d98cf178103b3 /Documentation | |
| parent | b30ea0536a45c0cd4b3c250f8cec1a0ed4e28ff5 (diff) | |
add extra free kbytes tunable
Add a userspace visible knob to tell the VM to keep an extra amount
of memory free, by increasing the gap between each zone's min and
low watermarks.
This is useful for realtime applications that call system
calls and have a bound on the number of allocations that happen
in any short time period. In this application, extra_free_kbytes
would be left at an amount equal to or larger than than the
maximum number of allocations that happen in any burst.
It may also be useful to reduce the memory use of virtual
machines (temporarily?), in a way that does not cause memory
fragmentation like ballooning does.
[ccross]
Revived for use on old kernels where no other solution exists.
The tunable will be removed on kernels that do better at avoiding
direct reclaim.
Change-Id: I765a42be8e964bfd3e2886d1ca85a29d60c3bb3e
Signed-off-by: Rik van Riel<riel@redhat.com>
Signed-off-by: Colin Cross <ccross@android.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/sysctl/vm.txt | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index d614a9b6a28..9dc0b8a780e 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -29,6 +29,7 @@ Currently, these files are in /proc/sys/vm: - dirty_writeback_centisecs - drop_caches - extfrag_threshold +- extra_free_kbytes - hugepages_treat_as_movable - hugetlb_shm_group - laptop_mode @@ -204,6 +205,21 @@ fragmentation index is <= extfrag_threshold. The default value is 500. ============================================================== +extra_free_kbytes + +This parameter tells the VM to keep extra free memory between the threshold +where background reclaim (kswapd) kicks in, and the threshold where direct +reclaim (by allocating processes) kicks in. + +This is useful for workloads that require low latency memory allocations +and have a bounded burstiness in memory allocations, for example a +realtime application that receives and transmits network traffic +(causing in-kernel memory allocations) with a maximum total message burst +size of 200MB may need 200MB of extra free memory to avoid direct reclaim +related latencies. + +============================================================== + hugepages_treat_as_movable This parameter controls whether we can allocate hugepages from ZONE_MOVABLE |