Messages in this thread | | | Date | Sun, 16 Apr 2023 01:42:44 +0800 | Subject | Re: [PATCH] mm: compaction: optimize compact_memory to comply with the admin-guide | From | Wen Yang <> |
| |
在 2023/4/13 00:54, Wen Yang 写道: > > 在 2023/4/12 04:48, Andrew Morton 写道: >> On Wed, 12 Apr 2023 02:24:26 +0800 wenyang.linux@foxmail.com wrote: >> >>> For the /proc/sys/vm/compact_memory file, the admin-guide states: >>> When 1 is written to the file, all zones are compacted such that free >>> memory is available in contiguous blocks where possible. This can be >>> important for example in the allocation of huge pages although >>> processes >>> will also directly compact memory as required >>> >>> But it was not strictly followed, writing any value would cause all >>> zones to be compacted. In some critical scenarios, some applications >>> operating it, such as echo 0, have caused serious problems. >> Really? You mean someone actually did this and didn't observe the >> effect during their testing? > > Thanks for your reply. > > Since /proc/sys/vm/compact_memory has been well documented for over a > decade: > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/Documentation/admin-guide/sysctl/vm.rst#n109 > > > it is believed that only writing 1 will trigger trigger all zones to > be compacted. > > Especially for those who write applications, they may only focus on > documentation and generally do not read kernel code. Moreover, such > problems are not easily detected through testing on low pressure > machines. > > Writing any meaningful or meaningless values will trigger it and > affect the entire server: > > # echo 1 > /proc/sys/vm/compact_memory > # echo 0 > /proc/sys/vm/compact_memory > # echo dead > /proc/sys/vm/compact_memory > # echo "hello world" > /proc/sys/vm/compact_memory > > The implementation of this high-risk operation may require following > the admin-guides. > > -- > > Best wishes, > > Wen > > Hello, do you think it's better to optimize the sysctl_compaction_handler code or update the admin-guide document?
--
Best wishes,
Wen
>>> It has been slightly optimized to comply with the admin-guide. >
| |