Re: [PATCH 00/40] Memory allocation profiling

Tejun Heo
2023-05-03T18:40:20Z

On Wed, May 03, 2023 at 08:19:24AM -1000, Tejun Heo wrote:
> > Taking a step back though, given the multitude of allocation sites in
> > the kernel, it's a bit odd that the only accounting we do is the tiny
> > fraction of voluntary vmstat/meminfo reporting. We try to cover the
> > biggest consumers with this of course, but it's always going to be
> > incomplete and is maintenance overhead too. There are on average
> > several gigabytes in unknown memory (total - known vmstats) on our
> > machines. It's difficult to detect regressions easily. And it's per
> > definition the unexpected cornercases that are the trickiest to track
> > down. So it might be doable with BPF, but it does feel like the kernel
> > should do a better job of tracking out of the box and without
> > requiring too much plumbing and somewhat fragile kernel allocation API
> > tracking and probing from userspace.
>
> Yeah, easy / default visibility argument does make sense to me.

So, a bit of addition here. If this is the thrust, the debugfs part seems
rather redundant, right? That's trivially obtainable with tracing / bpf and
in a more flexible and performant manner. Also, are we happy with recording
just single depth for persistent tracking?

Thanks.

--
tejun