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AJvYcCUIKg5yXnazzJTeAFJeYDepEIiyWjfcIQJ/LgWB3CCIzgNmgzPNxu2GPfKxf02SHwGFKOouDZjlVQ==@kvack.org X-Gm-Message-State: AOJu0YymEVdD04f7SL4LPubJaEGDzviUQvA5NjL1I0HUmSHcYzFrWsnZ XjoznKAnkxF2YQLfeSra/oYSpvbOnowcvVbPIVoVVPh2ns5uN8LpGMfCCMUuh97k2heSWqDb4VM H4sC76KhlBI/NOq0KiNRjT/0RiUimWG/VIHlPxQ== X-Gm-Gg: ASbGncvfEqe04Cbasena9BSHK1K9ZAfFN3luThb/sIbLFJ2hrHvFTtoP9nZcre1LXqP Es3YJlgwvnNxwJYJ5kbUnap6dJFFKyv/IxPcfn3uN2jbg3V737j7sUHqEUI2nnPDle6TdIaQ9d0 ceJ5IAwfp6cErqyvm+4fwfh7tLdwq9SyJHZg== X-Google-Smtp-Source: AGHT+IEo7ARr7g02UpjCXpp5GUfKWlGgEmFddHaeQwxNo6PWnqJ2zIiDARe5QyTYEKSdmvHqXaz07LR62euwob5p1Zg= X-Received: by 2002:a05:6902:140b:b0:e6b:80e3:2d00 with SMTP id 3f1490d57ef6-e73167d2953mr3499792276.17.1745593085330; Fri, 25 Apr 2025 07:58:05 -0700 (PDT) MIME-Version: 1.0 References: <20250424153815.4003-1-haowenchao22@gmail.com> <8905cbf7-7507-44de-8721-b3e75e80732b@linux.alibaba.com> In-Reply-To: <8905cbf7-7507-44de-8721-b3e75e80732b@linux.alibaba.com> From: Wenchao Hao Date: Fri, 25 Apr 2025 22:57:54 +0800 X-Gm-Features: ATxdqUEg70XJjGEjqzqthCjr_rv-cR_B85mtW4y2_0_YdVO9cQCkVBrryBfOaCY Message-ID: Subject: Re: [PATCH] mm/compaction: do not break pages whose order is larger than target order To: Baolin Wang Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4DA5E1C0012 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: g9omy98d3jr3qgpmyd8abf1fc5toeywr X-HE-Tag: 1745593086-77202 X-HE-Meta: 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 rIaYK+iY bUmUa2Vh2LM0fmyvY4YRR+rJTleoJnLKnDnRXYmYyUshmyUtW0hoUMWsMYl2uZaPT1drNqBBiHWEl+NsJ/MAqHPc9RFYphOwsSaQlO4oSWUikcs0czdHd1mNCe1uX53fwXbFd/KrIo/YfGsFq6IXV7jlwIx89K+uey8okA0jaVawCbLWu45lUCqYHTlkryFQXMsxfyedjDqKuMIQlDxBEderFUhqfMNa2YLnKWJ3fOQIazgK0xnrYKrkQseUXluKHmdBHBratm0O9JBEoYXWsnKjn/ZDDuWTJIB2tMBQPuVOYqPc406pcH9Zk3zbHWE2BFqwJKESdak2GRnSKuCl7A3fRmnbPRxUGgljJX4vQxtjS04wgqIumeZeMxOxHaL3tbzbTs2jkyGsFG18= 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: List-Subscribe: List-Unsubscribe: On Fri, Apr 25, 2025 at 2:53=E2=80=AFPM Baolin Wang wrote: > > > > On 2025/4/24 23:38, Wenchao Hao wrote: > > When scanning free pages for memory compaction, if the compaction targe= t > > order is explicitly specified, do not split pages in buddy whose order > > are larger than compaction target order. > > We've already checked this in suitable_migration_target(), so how did > you observe that there are still attempts to isolate such non-suitable > free large folios? Please explain your usecase in detail. > I found such non-suitable during testing proactive compaction on android device (6.6 kernel), and I want to use proactive compaction to produce order4 pages for mthp. The test device did not include your patch "mm: compaction: limit the suita= ble target page order to be less than cc->order". However, from the analysis of the code flow, even if it is included, similar non-suitable free large folios may still appear. suitable_migration_target() only check before isolate_freepages_block(), an= d check is based on the starting page of pageblock. If the target order is relatively small(order4 for example), just one check= in suitable_migration_target() is not enough, because there may be other free folios which are larger than order4 in this pageblock. > > Signed-off-by: Wenchao Hao > > --- > > mm/compaction.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/mm/compaction.c b/mm/compaction.c > > index 3925cb61dbb8..b0ed0831c400 100644 > > --- a/mm/compaction.c > > +++ b/mm/compaction.c > > @@ -656,6 +656,17 @@ static unsigned long isolate_freepages_block(struc= t compact_control *cc, > > > > /* Found a free page, will break it into order-0 pages */ > > order =3D buddy_order(page); > > + > > + /* > > + * Do not break free pages whose order is larger than > > + * compact's desired order > > + */ > > + if (cc->order !=3D -1 && order >=3D cc->order) { > > + blockpfn +=3D (1 << order) - 1; > > + page +=3D (1 << order) - 1; > > + goto isolate_fail; > > + } > > + > > isolated =3D __isolate_free_page(page, order); > > if (!isolated) > > break;