From nobody Mon Feb 9 16:06:31 2026 Received: from invmail4.hynix.com (exvmail4.hynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 31293DDB6 for ; Thu, 11 Jan 2024 06:23:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-d6dff70000001748-fc-659f85c84c60 From: Byungchul Park To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: kernel_team@skhynix.com, akpm@linux-foundation.org, ying.huang@intel.com, namit@vmware.com, xhao@linux.alibaba.com, mgorman@techsingularity.net, hughd@google.com, willy@infradead.org, david@redhat.com, peterz@infradead.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com Subject: [v5 7/7] mm: Pause migrc mechanism at high memory pressure Date: Thu, 11 Jan 2024 15:07:57 +0900 Message-Id: <20240111060757.13563-8-byungchul@sk.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20240111060757.13563-1-byungchul@sk.com> References: <20240111060757.13563-1-byungchul@sk.com> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrMLMWRmVeSWpSXmKPExsXC9ZZnke6J1vmpBt+OS1rMWb+GzeLzhn9s Fi82tDNafF3/i9ni6ac+FovLu+awWdxb85/V4vyutawWO5buY7K4dGABk8X1XQ8ZLY73HmCy 2LxpKrPF7x9AdXOmWFmcnDWZxUHA43trH4vHgk2lHptXaHks3vOSyWPTqk42j02fJrF7vDt3 jt3jxIzfLB47H1p6zDsZ6PF+31U2j62/7Dw+b5LzeDf/LVsAXxSXTUpqTmZZapG+XQJXRuvT 24wF15Qq7p/7wt7AOEGmi5GTQ0LAROLXs9WMXYwcYPbXpUogYTYBdYkbN34yg9giAmYSB1v/ sHcxcnEwCzxgkpj7dgUjSEJYwFniypE37CA2i4CqROeWKWANvAKmEvv6/7NAzJeXWL3hAFic E2jQhcOzwHYJAdU8aqsDmSkh8J1N4tSzHmaIekmJgytusExg5F3AyLCKUSgzryw3MTPHRC+j Mi+zQi85P3cTIzDol9X+id7B+OlC8CFGAQ5GJR7eB4vmpQqxJpYVV+YeYpTgYFYS4VX4PCdV iDclsbIqtSg/vqg0J7X4EKM0B4uSOK/Rt/IUIYH0xJLU7NTUgtQimCwTB6dUA2NK4BODuvaY 85cFJTwi2gO2xOTpXdLxvB3rWPEvRO3BVrPfk2a/mLP0+O0inqUT706TTah6NNH0uJH4iclr Pt/dVa+umMV6Z9WRz9p28tvio3J3Gu/8fDNWbOU7j4txHAvdkpoumdT7HLhWKNuyKt/lit/x yiS/n25KJz/XTOMoPKi/aJ3Yu0glluKMREMt5qLiRAA8WMaJdgIAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrFLMWRmVeSWpSXmKPExsXC5WfdrHuidX6qwatdfBZz1q9hs/i84R+b xYsN7YwWX9f/YrZ4+qmPxeLw3JOsFpd3zWGzuLfmP6vF+V1rWS12LN3HZHHpwAImi+u7HjJa HO89wGSxedNUZovfP4Dq5kyxsjg5azKLg6DH99Y+Fo8Fm0o9Nq/Q8li85yWTx6ZVnWwemz5N Yvd4d+4cu8eJGb9ZPHY+tPSYdzLQ4/2+q2wei198YPLY+svO4/MmOY9389+yBfBHcdmkpOZk lqUW6dslcGW0Pr3NWHBNqeL+uS/sDYwTZLoYOTgkBEwkvi5V6mLk5GATUJe4ceMnM4gtImAm cbD1D3sXIxcHs8ADJom5b1cwgiSEBZwlrhx5ww5iswioSnRumQLWwCtgKrGv/z8LiC0hIC+x esMBsDgn0KALh2cxguwSAqp51FY3gZFrASPDKkaRzLyy3MTMHFO94uyMyrzMCr3k/NxNjMAQ Xlb7Z+IOxi+X3Q8xCnAwKvHwGryclyrEmlhWXJl7iFGCg1lJhFfh85xUId6UxMqq1KL8+KLS nNTiQ4zSHCxK4rxe4akJQgLpiSWp2ampBalFMFkmDk6pBsYWjaCUo+t/GWzL++0tv2VW7tMf f5/V301+XBobrB6ynffi8vTP7d/z9nGtcdu9oVps9zaOiwtn+6oa7T+kw7hwkYHh6nQHY0HB m7xr52xLmj7vQtXT0wc2yarpOrhskFvDf2NXl4iBQWjBnS+Nxit2f65gPy+tfdJzQvmzsNOT /p/33HyE/9I+JZbijERDLeai4kQAdp/uwF0CAAA= X-CFilter-Loop: Reflected Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Regression was observed when the system is in high memory pressure with swap on, where migrc might keep a number of folios in its pending queue, which possibly makes it worse. So temporarily prevented migrc from working on that condition. Signed-off-by: Byungchul Park --- mm/internal.h | 20 ++++++++++++++++++++ mm/migrate.c | 16 ++++++++++++++++ mm/page_alloc.c | 13 +++++++++++++ 3 files changed, 49 insertions(+) diff --git a/mm/internal.h b/mm/internal.h index dc72a04d33a8..cade8219b417 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1295,6 +1295,8 @@ static inline void shrinker_debugfs_remove(struct den= try *debugfs_entry, #endif /* CONFIG_SHRINKER_DEBUG */ =20 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH +extern atomic_t migrc_pause_cnt; + /* * Reset the indicator indicating there are no writable mappings at the * beginning of every rmap traverse for unmap. Migrc can work only when @@ -1323,6 +1325,21 @@ static inline bool can_migrc_test(void) return current->can_migrc && current->tlb_ubc_ro.flush_required; } =20 +static inline void migrc_pause(void) +{ + atomic_inc(&migrc_pause_cnt); +} + +static inline void migrc_resume(void) +{ + atomic_dec(&migrc_pause_cnt); +} + +static inline bool migrc_paused(void) +{ + return !!atomic_read(&migrc_pause_cnt); +} + /* * Return the number of folios pending TLB flush that have yet to get * freed in the zone. @@ -1340,6 +1357,9 @@ bool migrc_flush_free_folios(void); static inline void can_migrc_init(void) {} static inline void can_migrc_fail(void) {} static inline bool can_migrc_test(void) { return false; } +static inline void migrc_pause(void) {} +static inline void migrc_resume(void) {} +static inline bool migrc_paused(void) { return false; } static inline int migrc_pending_nr_in_zone(struct zone *z) { return 0; } static inline bool migrc_flush_free_folios(void) { return false; } #endif diff --git a/mm/migrate.c b/mm/migrate.c index 181bfe260442..d072591c6ce6 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -62,6 +62,12 @@ static struct tlbflush_unmap_batch migrc_ubc; static LIST_HEAD(migrc_folios); static DEFINE_SPINLOCK(migrc_lock); =20 +/* + * Increase on entry of handling high memory pressure e.g. direct + * reclaim, decrease on the exit. See __alloc_pages_slowpath(). + */ +atomic_t migrc_pause_cnt =3D ATOMIC_INIT(0); + /* * Need to synchronize between TLB flush and managing pending CPUs in * migrc_ubc. Take a look at the following scenario: @@ -1892,6 +1898,7 @@ static int migrate_pages_batch(struct list_head *from, */ init_tlb_ubc(&pending_ubc); do_migrc =3D (reason =3D=3D MR_DEMOTION || reason =3D=3D MR_NUMA_MISPLACE= D); + do_migrc =3D do_migrc && !migrc_paused(); =20 for (pass =3D 0; pass < nr_pass && retry; pass++) { retry =3D 0; @@ -1930,6 +1937,15 @@ static int migrate_pages_batch(struct list_head *fro= m, continue; } =20 + /* + * In case that the system is in high memory + * pressure, give up migrc mechanism this turn. + */ + if (unlikely(do_migrc && migrc_paused())) { + fold_ubc(tlb_ubc, &pending_ubc); + do_migrc =3D false; + } + can_migrc_init(); rc =3D migrate_folio_unmap(get_new_folio, put_new_folio, private, folio, &dst, mode, reason, diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6ef0c22b1109..366777afce7f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4072,6 +4072,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int o= rder, unsigned int cpuset_mems_cookie; unsigned int zonelist_iter_cookie; int reserve_flags; + bool migrc_paused =3D false; =20 restart: compaction_retries =3D 0; @@ -4203,6 +4204,16 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int = order, if (page) goto got_pg; =20 + /* + * The system is in very high memory pressure. Pause migrc from + * expanding its pending queue temporarily. + */ + if (!migrc_paused) { + migrc_pause(); + migrc_paused =3D true; + migrc_flush_free_folios(); + } + /* Caller is not willing to reclaim, we can't balance anything */ if (!can_direct_reclaim) goto nopage; @@ -4330,6 +4341,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int o= rder, warn_alloc(gfp_mask, ac->nodemask, "page allocation failure: order:%u", order); got_pg: + if (migrc_paused) + migrc_resume(); return page; } =20 --=20 2.17.1