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Wed, 26 Jun 2024 18:54:25 -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: Lance Yang Date: Thu, 27 Jun 2024 09:54:14 +0800 Message-ID: Subject: Re: [PATCH 2/2] kpageflags: fix wrong KPF_THP on non-pmd-mappable compound pages To: Ryan Roberts Cc: Zi Yan , ran xiaokai , akpm@linux-foundation.org, willy@infradead.org, vbabka@suse.cz, svetly.todorov@memverge.com, ran.xiaokai@zte.com.cn, baohua@kernel.org, peterx@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, David Hildenbrand , Baolin Wang , Kefeng Wang , Barry Song <21cnbao@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 679F7140006 X-Stat-Signature: j6uf1fpors46zn9pmn7khpay6spd36bd X-Rspam-User: X-HE-Tag: 1719453267-504049 X-HE-Meta: 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 QmPhFPkB e41fv2v/mjm29bqWrZWsmJ2z9YLttKyJwN1/bUDwOKti3h51WQrODM7nMbwvAWNg2/EI7UEB1ECQ7Fl08Q42//1p+9bKyqJ0YeN2EtQXONu28snevXfBf/YJ/+hYgeAVs0MDYolDl37fXl6jlCcM15xgZ222VGkc4c5V7Ecd/CIX72jBdRxDerMXLJJzT8Mizhhp4uiEQaAOAqUYO9K7h20imJYQJ8EcFvyvKRM1yrh4rGb7WkV8lH7Uk9JOYQOe4FOBncZgNKx6CF5YzY4zvbETsJoe8+2cFizSTjmtnyUKQJFy3h/NkZOGE/gmt0cP6Kxrmb98v2Z7bJ8VfDT/ZMCdNzee5hdbB7qHMzAJ7P7piPmAIa2badLGDW9icPJMAc7iVycfYIKh3moGnJOJwW8FTp+1SMeMfXAOkMA8QSkUhzsBr1Jhu1pYocG/eV7zLF2DcqcU91BnmLl3CYI83GQHHVA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, 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 Wed, Jun 26, 2024 at 10:42=E2=80=AFPM Ryan Roberts wrote: > > On 26/06/2024 15:40, 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 a= s it is > >> currently configured? > >> > >> I would argue that mTHP is still THP so should still have the flag. An= d 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 = compat > >> issues as is. > >> > >> Also, the script at tools/mm/thpmaps relies on KPF_THP being set for a= ll mTHP > >> sizes to function correctly. So that would need to be reworked if maki= ng 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 coun= ters > > consistent. See recent commits on adding mTHP counters: > > ec33687c6749 ("mm: add per-order mTHP anon_fault_alloc and anon_fault_f= allback > > counters"), 1f97fd042f38 ("mm: shmem: add mTHP counters for anonymous s= hmem") > > > > 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. > > That would work for me, assuming we have KPF bits to spare? +1 Let's check on that and see if we're good ;) Thanks, Lance >