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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: uyf1sb6gujcxpy4dm66jjyx1tx7qt8uu X-Rspamd-Queue-Id: A12941A0019 X-HE-Tag: 1677175741-651488 X-HE-Meta: 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 yBMN2RPT XGULhlpupHrLmuLf94S3bTDaqRhLdzuN5BoFAjEyt83s0tJiaP6VJh+duGFp1lV2Nb6QnXa7lLZRzPsAp7dJVA4ipUvpz+dGyaeQFKDcZlJTIbOV2e6c6/q9MiIqo7rTjVY7nK0g1iVF3aNQWyw2kji7sqyE2jbHUvXFqXesYBGNOgJBjNv9TPtrBXubB5K5f3pdUKtikMoSz0O4PXvkxMydcOAEWFrMdfCmHXyGbBi5lsRaM1lslAES76mYyrUVw4t3zwskvVwJPo5HUwH1WejXug1jvE6F56f6m3ORxiVugXzXUPxaW2e/aXw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 23, 2023 at 10:43=E2=80=AFAM Sean Christopherson wrote: > > On Thu, Feb 16, 2023, Yu Zhao wrote: > > An existing selftest can quickly demonstrate the effectiveness of this > > patch. On a generic workstation equipped with 128 CPUs and 256GB DRAM: > > Not my area of maintenance, but a non-existent changelog (for all intents= and > purposes) for a change of this size and complexity is not acceptable. Will fix. > > $ sudo max_guest_memory_test -c 64 -m 250 -s 250 > > > > MGLRU run2 > > --------------- > > Before ~600s > > After ~50s > > Off ~250s > > > > kswapd (MGLRU before) > > 100.00% balance_pgdat > > 100.00% shrink_node > > 100.00% shrink_one > > 99.97% try_to_shrink_lruvec > > 99.06% evict_folios > > 97.41% shrink_folio_list > > 31.33% folio_referenced > > 31.06% rmap_walk_file > > 30.89% folio_referenced_one > > 20.83% __mmu_notifier_clear_flush_young > > 20.54% kvm_mmu_notifier_clear_flush_young > > =3D> 19.34% _raw_write_lock > > > > kswapd (MGLRU after) > > 100.00% balance_pgdat > > 100.00% shrink_node > > 100.00% shrink_one > > 99.97% try_to_shrink_lruvec > > 99.51% evict_folios > > 71.70% shrink_folio_list > > 7.08% folio_referenced > > 6.78% rmap_walk_file > > 6.72% folio_referenced_one > > 5.60% lru_gen_look_around > > =3D> 1.53% __mmu_notifier_test_clear_young > > Do you happen to know how much of the improvement is due to batching, and= how > much is due to using a walkless walk? No. I have three benchmarks running at the moment: 1. Windows SQL server guest on x86 host, 2. Apache Spark guest on arm64 host, and 3. Memcached guest on ppc64 host. If you are really interested in that, I can reprioritize -- I need to stop 1) and use that machine to get the number for you. > > @@ -5699,6 +5797,9 @@ static ssize_t show_enabled(struct kobject *kobj,= struct kobj_attribute *attr, c > > if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YO= UNG)) > > caps |=3D BIT(LRU_GEN_NONLEAF_YOUNG); > > > > + if (kvm_arch_has_test_clear_young() && get_cap(LRU_GEN_SPTE_WALK)= ) > > + caps |=3D BIT(LRU_GEN_SPTE_WALK); > > As alluded to in patch 1, unless batching the walks even if KVM does _not= _ support > a lockless walk is somehow _worse_ than using the existing mmu_notifier_c= lear_flush_young(), > I think batching the calls should be conditional only on LRU_GEN_SPTE_WAL= K. Or > if we want to avoid batching when there are no mmu_notifier listeners, pr= obe > mmu_notifiers. But don't call into KVM directly. I'm not sure I fully understand. Let's present the problem on the MM side: assuming KVM supports lockless walks, batching can still be worse (very unlikely), because GFNs can exhibit no memory locality at all. So this option allows userspace to disable batching. I fully understand why you don't want MM to call into KVM directly. No acceptable ways to set up a clear interface between MM and KVM other than the MMU notifier?