On Tue 21-09-21 20:12:08, Vishnu Rangayyan wrote:
On 9/21/21 5:59 AM, Michal Hocko wrote:
[...]
Why is fsync helping at all? Why do we need a new sysctl to address the problem and how does it help to prevent the memcg OOM. Also why is this a problem in the first place.
The simple intent is to allow the core dumping to succeed in low memory situations where the dump_emit doesn't tip over the thing and trigger the oom-killer. This change avoids only that particular issue.
How does it avoid that?
Agree, its not the actual problem at all. If the core dumping fails, that sometimes prevents or delays looking into the actual issue. The sysctl was to allow disabling this behavior or to fine tune for special cases such as limited memory environments.
Please note that any sysctl is an userspace API that has to be maintained effectivelly for ever so there should be a very good reason and a strong justification to add one. I do not see that to be case here.