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b=Ss5/7B8P4iVJPoxo3V8uqSXR32uktKCar1PAxSEIUAkKWjK8zbtQ2aArLbreU0Dd/ 7ARsemNGFI9DMTx4NFvVe00i0qE7iAmuiAjGwFAfU5HJ6PdTHbtQw2OOLGuUs+6rgx 3EbBDikXjrhTlqc4ygMfDWESvYheqwElZvDOrvmIvINI37/nUboqOPddbJ8SCbzO6r /2Z8H9gMlcozH2lAEvmRZJUwubNIOEKzpesBcu5K+64kLbqGZNzYKkVqvSJQYSGzpj WE7rsyuS5eyLMDPAOIorSpQCck6JXOPZfxf0+kgMnp9w+AdSjyvjky6mwfDHk60mnt pGTM/sFIr1riw== Message-ID: <9890b8f5-69b9-49bc-8ed6-ea47723b644e@kernel.org> Date: Wed, 17 Jun 2026 20:57:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 3/3] mm/compaction: respect compact_unevictable_allowed in alloc_contig path Content-Language: en-US To: Wandun Chen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: akpm@linux-foundation.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@kernel.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, Alexander.Krabler@kuka.com References: <20260604023812.3700316-1-chenwandun1@gmail.com> <20260604023812.3700316-4-chenwandun1@gmail.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D11D540002 X-Rspam-User: X-Stat-Signature: yb5kbrydkped85iuuwsef8xg7eewhmd4 X-Rspamd-Server: rspam09 X-HE-Tag: 1781722652-589615 X-HE-Meta: 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 Vd4hNhNT km+IEwX18TWZQQ4BpkV3VY8MVJxaPP0sM1ZjsmHGsDV8Vg3xC72yr3vZH/XnRquUt4wa67IrFpbOEPTK57OVBpsbdcKbl/ZdTnxpnV4RO8O+6k2QArJPNxR/Vx30cE+hiE3YNcOJn+p0j0ZZyochWqid8icGjTFXBq+TiOa5qlUITZSidxXr2VEZTng+dCugcV5ZN57rHpoZoD1hmI/ZRJd2osNAJvwvMlDfj+c2gIaEYzfI2G+iQsndno42fJDxVrY2RJESFpGw2ljhgSooNVBeP4IYLmTpttqX9om0zEp93YMvXGkS7jDxWHEOHOC+vk13ZJqvWI1N2ctwbTH1Z6hjftrzWA1DpHBav1uH2GcRfVGQSRULTg3iquXDcWEwAzD4U6nGd36zIargOLK0AM2T9cqX4ba7kAQW9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/4/26 04:38, Wandun Chen wrote: > From: Wandun Chen > > vm.compact_unevictable_allowed=0 is used to prevent compacting > unevictable pages. However, isolate_migratepages_range() passes > ISOLATE_UNEVICTABLE regardless of this sysctl, so the setting > has no effect in the alloc_contig path. > > Fix it by: > - Keep ISOLATE_UNEVICTABLE for CMA allocation, discussed in [1]. > - Honour sysctl_compact_unevictable_allowed for non-CMA allocation. > > Suggested-by: Vlastimil Babka > Signed-off-by: Wandun Chen > Link: https://lore.kernel.org/all/25ba0d77-eb61-4efc-b2fc-73878cbd85c1@suse.cz/ [1] There was also the "Ideally by not having mlock'd pages in CMA areas at all." part. Is it the case? It was more elaborated here: https://lore.kernel.org/all/CAPTztWZpnX1j8-7yeppVUsxE=O9hbVeqricDjZt8_pnN7a-kBQ@mail.gmail.com/ > --- > include/linux/compaction.h | 6 ++++++ > mm/compaction.c | 9 +++++++-- > mm/internal.h | 1 + > mm/page_alloc.c | 2 ++ > 4 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/include/linux/compaction.h b/include/linux/compaction.h > index f29ef0653546..04e60f65b976 100644 > --- a/include/linux/compaction.h > +++ b/include/linux/compaction.h > @@ -106,6 +106,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order, > extern void __meminit kcompactd_run(int nid); > extern void __meminit kcompactd_stop(int nid); > extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx); > +extern bool compaction_allow_unevictable(void); > > #else > static inline void reset_isolation_suitable(pg_data_t *pgdat) > @@ -131,6 +132,11 @@ static inline void wakeup_kcompactd(pg_data_t *pgdat, > { > } > > +static inline bool compaction_allow_unevictable(void) > +{ > + return true; > +} > + > #endif /* CONFIG_COMPACTION */ > > struct node; > diff --git a/mm/compaction.c b/mm/compaction.c > index 007d5e00a8ae..a10acb273454 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1341,6 +1341,7 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, > unsigned long end_pfn) > { > unsigned long pfn, block_start_pfn, block_end_pfn; > + isolate_mode_t mode = cc->allow_unevictable ? ISOLATE_UNEVICTABLE : 0; > int ret = 0; > > /* Scan block by block. First and last block may be incomplete */ > @@ -1360,8 +1361,7 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, > block_end_pfn, cc->zone)) > continue; > > - ret = isolate_migratepages_block(cc, pfn, block_end_pfn, > - ISOLATE_UNEVICTABLE); > + ret = isolate_migratepages_block(cc, pfn, block_end_pfn, mode); > > if (ret) > break; > @@ -1902,6 +1902,11 @@ typedef enum { > * compactable pages. > */ > static int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT; > + > +bool compaction_allow_unevictable(void) > +{ > + return sysctl_compact_unevictable_allowed; > +} > /* > * Tunable for proactive compaction. It determines how > * aggressively the kernel should compact memory in the > diff --git a/mm/internal.h b/mm/internal.h > index 181e79f1d6a2..163f9d6b37f3 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1052,6 +1052,7 @@ struct compact_control { > * ensure forward progress. > */ > bool alloc_contig; /* alloc_contig_range allocation */ > + bool allow_unevictable; /* Allow isolation of unevictable folios */ > }; > > /* > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 81a9d4d1e6c0..1cf9d4a3b14c 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7118,6 +7118,8 @@ int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end, > .ignore_skip_hint = true, > .no_set_skip_hint = true, > .alloc_contig = true, > + .allow_unevictable = !!(alloc_flags & ACR_FLAGS_CMA) || > + compaction_allow_unevictable(), > }; > INIT_LIST_HEAD(&cc.migratepages); > enum pb_isolate_mode mode = (alloc_flags & ACR_FLAGS_CMA) ?