Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page

From: Chris Down <[email-masked]>
Date: Fri, 29 May 2020 02:56:44 +0100

Yafang Shao writes:
>Look at this patch[1] carefully you will find that it introduces the
>same issue that I tried to fix in another patch [2]. Even more sad is
>these two patches are in the same patchset. Although this issue isn't
>related with the issue found by Naresh, we have to ask ourselves why
>we always make the same mistake ?
>One possible answer is that we always forget the lifecyle of
>memory.emin before we read it. memory.emin doesn't have the same
>lifecycle with the memcg, while it really has the same lifecyle with
>the reclaimer. IOW, once a reclaimer begins the protetion value should
>be set to 0, and after we traversal the memcg tree we calculate a
>protection value for this reclaimer, finnaly it disapears after the
>reclaimer stops. That is why I highly suggest to add an new protection
>member in scan_control before.

I agree with you that the e{min,low} lifecycle is confusing for everyone -- the 
only thing I've not seen confirmation of is any confirmed correlation with the 
i386 oom killer issue. If you've validated that, I'd like to see the data :-)