On Wed 04-04-18 16:59:18, Joel Fernandes wrote: > Hi Steve, > > On Wed, Apr 4, 2018 at 9:18 AM, Joel Fernandes <joelaf@xxxxxxxxxx> wrote: > > On Wed, Apr 4, 2018 at 9:13 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > [..] > >>> > >>> Also, I agree with the new patch and its nice idea to do that. > >> > >> Thanks, want to give it a test too? > > With the latest tree and the below diff, I can still OOM-kill a victim > process doing a large buffer_size_kb write: > > I pulled your ftrace/core and added this: > + /* > i = si_mem_available(); > if (i < nr_pages) > return -ENOMEM; > + */ > > Here's a run in Qemu with 4-cores 1GB total memory: > > bash-4.3# ./m -m 1M & > [1] 1056 > bash-4.3# > bash-4.3# > bash-4.3# > bash-4.3# echo 10000000 > /d/tracing/buffer_size_kb > [ 33.213988] Out of memory: Kill process 1042 (bash) score > 1712050900 or sacrifice child > [ 33.215349] Killed process 1056 (m) total-vm:9220kB, > anon-rss:7564kB, file-rss:4kB, shmem-rss:640kB OK, so the reason your memory hog is triggered is that your echo is built-in and we properly select bask as an oom_origin but then another clever heuristic jumps in and tries to reduce the damage by sacrificing a child process. And your memory hog runs as a child from the same bash session. I cannot say I would love this heuristic. In fact I would really love to dig it deep under the ground. But this is a harder sell than it might seem. Anyway is your testing scenario really representative enough to care? Does the buffer_size_kb updater runs in the same process as any large memory process? > bash: echo: write error: Cannot allocate memory > [1]+ Killed ./m -m 1M > bash-4.3# > -- -- Michal Hocko SUSE Labs
