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Howlett" , Kiryl Shutsemau , Vlastimil Babka , Kairui Song , Mikhail Zaslonko , Vasily Gorbik , Baolin Wang , Barry Song , Dev Jain , Lance Yang , Nico Pache , Ryan Roberts , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260527204757.2544958-1-hannes@cmpxchg.org> <20260527204757.2544958-10-hannes@cmpxchg.org> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Usama Arif In-Reply-To: <20260527204757.2544958-10-hannes@cmpxchg.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: B12A640018 X-Stat-Signature: zmagbpdosm8y7osy5g49ch8mmki9eea9 X-Rspamd-Server: rspam06 X-HE-Tag: 1779975142-516160 X-HE-Meta: U2FsdGVkX1+XKgYgSD6bWfvGWEVzJO6WLIU6+pgMznZ8W+8s1Vs1PiMe6uI2UXNRy/ERHcql/CLN/+Vorj9DMWDu+7KIcCSDojqEFS0EEsOPmKZ8BIqLjuJsLgQFud5Ca7A3i1SXDSPpXPdbeOJlc8+UtN1cP5Y6mmeU4WekFrhHND3sG9f6lYl3Q3TH2/IUpGrTh7L11kKWw9RzTEdSE1SikBL4T5JHTdrJLLA6pImX12iE+WaPcc0KrBSz7bCwc5Tcq5hEtHF4g1+BITS30/w4WY2cI8Cx6+GBpiaQU2THw0K1Zsfp+ejkOg89jMKgnT28Dwxz+ols+s85fR6/YdltzYKAloqHNdUEDFxrciMjUefnczd9sjYjxAKppwixeN/WQiOIrE64oJ5Z9Eus+oW9s8waF8wt1dFiacXjJRoNp5kLBkIg3BdogIxuQ1yilGsPFJCcN9jI+ZEGj9dyiOYzIWhgSlye4N+r/Z/tm59TubtqkGBcykMu3B9nvplX+TnZwEgUsEp6rX9jFB0YLogJXiGGRTV0dE+F5c2oVM3CUesRwuyQk9C282+/k9ptfpi4yz2Wn+5MP3ilG417Zf6W4sqQQQmNE10Ap1elpObx0Db2X3uM/1wio/ObzRra0y/dJvS5c84APmYyczlPr4csyPX8vKZYS85grmhbrh1DeRyZDSNvBl6TgUlRYEtRRTqHFwQ5cMmT/3+y5BQMZxh+AbiPIEVEQ970mAolXTgVIjf3W7IbPIGxxgZT3OqcyFWqYquE+UOy4s57X67L67gkhgfWmS056Uv1n8FDYJbqcDU87huqk4kSV2QwM2wW2MVXJRZphoNp84s49/kzwJD3wV9ZmytZNrti7IBemexQe6JhtRUZUbtPmZfuDudhJSIbJkIQGpnqwGtMlF+4ZffMjUa87D+051TCNBegRTTxn6ZPG0K3wbhB/BzSBr8Jd9bo0xCBCP4n/UZU0SQ RIRjVa8j d3PUhC0F+CPDtkvETmpBZq2jAH+tXp8oVin1f0AtHM0dqGQPKy7Md2ylRrnZrgDHUnzB4DWc0vmtjfv0dsJISfQ7w4aI6yYF106Sfq7OON3Lbx7x/QAI5LNGIxWzwnfgGMgMlE3DdpmPSPPYRDBtIhRJhi5F3Nqa7lPefrrl1ezLrFxidg8U954k8AqpNCUMjysTndZUq/1ECzaYxE+IK0iMP9vPM+StLyUgjEDCmFN/BWHD4uHhzAoWSpLEbu4fyH7g0wI2oUSaf3VTr12rzWYZD/5tF5nIqdQZZIidLmfbyQhfThIKa4dKMi2ZLHyo9hPd1079RrrFOpZk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 27/05/2026 21:45, Johannes Weiner wrote: > The deferred split queue handles cgroups in a suboptimal fashion. The > queue is per-NUMA node or per-cgroup, not the intersection. That means > on a cgrouped system, a node-restricted allocation entering reclaim > can end up splitting large pages on other nodes: > > alloc/unmap > deferred_split_folio() > list_add_tail(memcg->split_queue) > set_shrinker_bit(memcg, node, deferred_shrinker_id) > > for_each_zone_zonelist_nodemask(restricted_nodes) > mem_cgroup_iter() > shrink_slab(node, memcg) > shrink_slab_memcg(node, memcg) > if test_shrinker_bit(memcg, node, deferred_shrinker_id) > deferred_split_scan() > walks memcg->split_queue > > The shrinker bit adds an imperfect guard rail. As soon as the cgroup > has a single large page on the node of interest, all large pages owned > by that memcg, including those on other nodes, will be split. > > list_lru properly sets up per-node, per-cgroup lists. As a bonus, it > streamlines a lot of the list operations and reclaim walks. It's used > widely by other major shrinkers already. Convert the deferred split > queue as well. > > The list_lru per-memcg heads are instantiated on demand when the first > object of interest is allocated for a cgroup, by calling > folio_memcg_alloc_deferred(). Add calls to where splittable pages are > created: anon faults, swapin faults, khugepaged collapse. > > These calls create all possible node heads for the cgroup at once, so > the migration code (between nodes) doesn't need any special care. > > Reported-by: Mikhail Zaslonko > Tested-by: Mikhail Zaslonko > Acked-by: Shakeel Butt > Reviewed-by: Lorenzo Stoakes (Oracle) > Signed-off-by: Johannes Weiner > --- > include/linux/huge_mm.h | 7 +- > include/linux/memcontrol.h | 4 - > include/linux/mmzone.h | 12 -- > mm/huge_memory.c | 364 +++++++++++++------------------------ > mm/internal.h | 2 +- > mm/khugepaged.c | 5 + > mm/memcontrol.c | 12 +- > mm/memory.c | 4 + > mm/mm_init.c | 15 -- > mm/swap_state.c | 10 + > 10 files changed, 150 insertions(+), 285 deletions(-) > [...] > diff --git a/mm/memory.c b/mm/memory.c > index 135f5c0f57bd..f22e61d8c8de 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5222,6 +5222,10 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) > folio_put(folio); > goto next; > } > + if (order > 1 && folio_memcg_alloc_deferred(folio)) { > + folio_put(folio); Ah sorry, should have caught this in the previous version, do we need count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK); here? or maybe we just goto next instead of goto fallback and trty next viable order? > + goto fallback; > + } > folio_throttle_swaprate(folio, gfp); > /* > * When a folio is not zeroed during allocation