Messages in this thread | | | Subject | Re: [RFC PATCH v2 0/4] Eliminate zone->lock contention for will-it-scale/page_fault1 and parallel free | From | Daniel Jordan <> | Date | Thu, 22 Mar 2018 07:20:14 -0400 |
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On 03/21/2018 09:30 PM, Aaron Lu wrote: > On Wed, Mar 21, 2018 at 01:44:25PM -0400, Daniel Jordan wrote: >> On 03/20/2018 04:54 AM, Aaron Lu wrote: >> ...snip... >>> reduced zone->lock contention on free path from 35% to 1.1%. Also, it >>> shows good result on parallel free(*) workload by reducing zone->lock >>> contention from 90% to almost zero(lru lock increased from almost 0 to >>> 90% though). >> >> Hi Aaron, I'm looking through your series now. Just wanted to mention that I'm seeing the same interaction between zone->lock and lru_lock in my own testing. IOW, it's not enough to fix just one or the other: both need attention to get good performance on a big system, at least in this microbenchmark we've both been using. > > Agree. > >> >> There's anti-scaling at high core counts where overall system page faults per second actually decrease with more CPUs added to the test. This happens when either zone->lock or lru_lock contention are completely removed, but the anti-scaling goes away when both locks are fixed. >> >> Anyway, I'll post some actual data on this stuff soon. > > Looking forward to that, thanks. > > In the meantime, I'll also try your lru_lock optimization work on top of > this patchset to see if the lock contention shifts back to zone->lock.
The lru_lock series I posted is pretty outdated by now, and I've got a totally new approach I plan to post soon, so it might make sense to wait for that.
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