On Thu 27-06-24 04:33:50, Yosry Ahmed wrote: > On Thu, Jun 27, 2024 at 12:13 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Wed 26-06-24 09:42:32, Xiu Jianfeng wrote: > > > Both the end of memory_stat_format() and memcg_stat_format() will call > > > WARN_ON_ONCE(seq_buf_has_overflowed()). However, memory_stat_format() > > > is the only caller of memcg_stat_format(), when memcg is on the default > > > hierarchy, seq_buf_has_overflowed() will be executed twice, so remove > > > the reduntant one. > > > > Shouldn't we rather remove both? Are they giving us anything useful > > actually? Would a simpl pr_warn be sufficient? Afterall all we care > > about is to learn that we need to grow the buffer size because our stats > > do not fit anymore. It is not really important whether that is an OOM or > > cgroupfs interface path. > > Is it possible for userspace readers to break if the stats are > incomplete? They will certainly get an imprecise picture. Sufficient to break I dunno. > If yes, I think WARN_ON_ONCE() may be prompted to make it > easier to catch and fix before deployment. The only advantage of WARN_ON_ONCE is that the splat is so verbose that it gets noticed. And also it panics the system if panic_on_warn is enabled. I do not particularly care about the latter but to me it seems like the warning is just an over reaction and a simple pr_warn should just achieve the similar effect - see my other reply -- Michal Hocko SUSE Labs
