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AJvYcCWNxUdGfQ2tG1VjgknaLt8Jxb7kw/ytM7rFUNBNWSPDrTgWeEKhopMmejSpqUmgjW+GicrRRHcYFBkqjD8aLxpDI5c= X-Gm-Message-State: AOJu0YzpKOJE/fZOAuiVbHsWgPouvI8pMeJQ3bhNYifGQ+PJkh+CfvT8 2McnA9IQHkHhowMlm5gkZ7g06DeYR3H8dIaccZ2yMNNLLjiD84ek8wXfbUqYyqxQilSVZhCX46K FLy7vnML5or8fqGLp9DXu5f5mXAc= X-Google-Smtp-Source: AGHT+IFfDa0ktIOys1TJVi0P9n6zh5dH5AKUYvUR9DtrBG4sqPeS33t4v0IsNlc0T9/CdRCN55Qh60RRnXX/dZ6KYyI= X-Received: by 2002:a67:bb03:0:b0:48f:8c83:dce9 with SMTP id ada2fe7eead31-48f8c83de6bmr929007137.29.1719461438197; Wed, 26 Jun 2024 21:10:38 -0700 (PDT) MIME-Version: 1.0 References: <20240626024924.1155558-1-ranxiaokai627@163.com> <20240626024924.1155558-3-ranxiaokai627@163.com> <1907a8c0-9860-4ca0-be59-bec0e772332b@arm.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Thu, 27 Jun 2024 16:10:26 +1200 Message-ID: Subject: Re: [PATCH 2/2] kpageflags: fix wrong KPF_THP on non-pmd-mappable compound pages To: Zi Yan Cc: Ryan Roberts , ran xiaokai , akpm@linux-foundation.org, willy@infradead.org, vbabka@suse.cz, svetly.todorov@memverge.com, ran.xiaokai@zte.com.cn, peterx@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, David Hildenbrand , Baolin Wang , Kefeng Wang , Lance Yang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4C3A02000E X-Stat-Signature: 1b465bg1bto5edpe3ojsaeh6udurijsx X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1719461439-976669 X-HE-Meta: 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 WTbMmdhP JWH5SbWLGYVPiz7STAaEokk0ZvI3ccZb1oMoE2myv0Rw+fO6gcnH4rBVuhe7KD0n+fvDIkLV3poHR99yqmI1fhGQT7MaIU969bTcBRe5sb6/oE2IXLPC+aJ07gOnaGi9X2G7eVTLxGHk3bYzydIwHJhHdCLln4sLlQTjDp5Mjyb9tub4I9jkeDCqNPgxA0G0yCR7nU84z4M6q1kYpjQv73jlsG3rkYvCiiT412/4TTex/cNU4UZhBS4nuHE/GnEQzpEVa6GlSNarGAURjoSaEB/ER6oUKIZgMsURLMi4URbSj9igje5FHvi7VqHwuJV4tMpjnDBS5zmDlfB7vITia5uC5d/EYRCJhGozuXKb/Qhd5h2epMik8CjXj3DtdmwgOh/Jr9VOcaPOgwFQcOhYImKKoqP9ErcFUqVQ48Fv4A8fhCac= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000024, 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 Thu, Jun 27, 2024 at 2:40=E2=80=AFAM Zi Yan wrote: > > On Wed Jun 26, 2024 at 7:07 AM EDT, Ryan Roberts wrote: > > On 26/06/2024 04:06, Zi Yan wrote: > > > On Tue Jun 25, 2024 at 10:49 PM EDT, ran xiaokai wrote: > > >> From: Ran Xiaokai > > >> > > >> KPF_COMPOUND_HEAD and KPF_COMPOUND_TAIL are set on "common" compound > > >> pages, which means of any order, but KPF_THP should only be set > > >> when the folio is a 2M pmd mappable THP. > > > > Why should KPF_THP only be set on 2M THP? What problem does it cause as= it is > > currently configured? > > > > I would argue that mTHP is still THP so should still have the flag. And= since > > these smaller mTHP sizes are disabled by default, only mTHP-aware user = space > > will be enabling them, so I'll naively state that it should not cause c= ompat > > issues as is. > > > > Also, the script at tools/mm/thpmaps relies on KPF_THP being set for al= l mTHP > > sizes to function correctly. So that would need to be reworked if makin= g this > > change. > > + more folks working on mTHP > > I agree that mTHP is still THP, but we might want different > stats/counters for it, since people might want to keep the old THP counte= rs > consistent. See recent commits on adding mTHP counters: > ec33687c6749 ("mm: add per-order mTHP anon_fault_alloc and anon_fault_fal= lback > counters"), 1f97fd042f38 ("mm: shmem: add mTHP counters for anonymous shm= em") > > and changes to make THP counter to only count PMD THP: > 835c3a25aa37 ("mm: huge_memory: add the missing folio_test_pmd_mappable()= for > THP split statistics") > > In this case, I wonder if we want a new KPF_MTHP bit for mTHP and some > adjustment on tools/mm/thpmaps. It seems we have to do this though I think keeping KPF_THP and adding a separate bit like KPF_PMD_MAPPED makes more sense. but those tools relying on KPF_THP need to realize this and check the new bit , which is not done now. whether the mTHP's name is mTHP or THP will make no difference for this case:-) > > > -- > Best Regards, > Yan, Zi > Thanks Barry