On Mon, Oct 31, 2022 at 9:21 AM Uladzislau Rezki <urezki@xxxxxxxxx> wrote: > > On Fri, Oct 28, 2022 at 09:23:47PM +0000, Joel Fernandes wrote: > > On Mon, Oct 24, 2022 at 09:48:19AM -0700, Paul E. McKenney wrote: > > > On Mon, Oct 24, 2022 at 06:25:30PM +0200, Uladzislau Rezki wrote: > > > > > > > > > > You guys might need to agree on the definition of "good" here. Or maybe > > > > > understand the differences in your respective platforms' definitions of > > > > > "good". ;-) > > > > > > > > > Indeed. Bad is when once per-millisecond infinitely :) At least in such use > > > > workload a can detect a power delta and power gain. Anyway, below is a new > > > > trace where i do not use "flush" variant for the kvfree_rcu(): > > > > > > > > <snip> > > > > 1. Home screen swipe: [...] > > > > 2. App launches: [...] > > > > <snip> > > > > > > > > it is much more better. But. As i wrote earlier there is a patch that i have submitted > > > > some time ago improving kvfree_rcu() batching: > > > > > > > > <snip> > > > > commit 51824b780b719c53113dc39e027fbf670dc66028 > > > > Author: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> > > > > Date: Thu Jun 30 18:33:35 2022 +0200 > > > > > > > > rcu/kvfree: Update KFREE_DRAIN_JIFFIES interval > > > > > > > > Currently the monitor work is scheduled with a fixed interval of HZ/20, > > > > which is roughly 50 milliseconds. The drawback of this approach is > > > > low utilization of the 512 page slots in scenarios with infrequence > > > > kvfree_rcu() calls. For example on an Android system: > > > > <snip> > > > > > > > > The trace that i posted was taken without it. > > > > > > And if I am not getting too confused, that patch is now in mainline. > > > So it does make sense to rely on it, then. ;-) > > > > Vlad's patch to change the KFREE_DRAIN_JIFFIES to 5 seconds seems reasonable > > to me. However, can we unify KFREE_DRAIN_JIFFIES and LAZY_FLUSH_JIFFIES ? > > > This is very good. > > Below is a plot that i have taken during one use-case. It is about three > apps usage in parallel. It was done by running "monkey" test: > > wget ftp://vps418301.ovh.net/incoming/monkey_3_apps_slab_usage_5_minutes.png > > i set up three apps as usage scenario: Google Chrome, YoTube and Camera. > I logged the Slab metric from the /proc/meminfo. Sampling rate is 0.1 second. > > Please have a look at results. It reflects what i am saying. non-flush > kvfree RCU variant makes a memory usage higher. What is not acceptable > for our mobile devices and workloads. That does look higher, though honestly about ~5%. But that's just the effect of more "laziness". The graph itself does not show a higher number of shrinker invocations, in fact I think shrinker invocations are not happening much that's why the slab holds more memory. The system may not be under memory pressure? Anyway, I agree with your point of view and I think my concern does not even occur with the latest patch on avoiding RCU that I posted [1], so I come in peace. [1] https://lore.kernel.org/rcu/20221029132856.3752018-1-joel@xxxxxxxxxxxxxxxxx/ I am going to start merging all the lazy patches to ChromeOS 5.10 now including your kfree updates, except for [1] while we discuss it.
