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Fri, 12 Sep 2025 11:44:19 -0400 (EDT) Date: Fri, 12 Sep 2025 16:44:17 +0100 From: Kiryl Shutsemau To: Pedro Falcato Cc: David Hildenbrand , Johannes Weiner , Nico Pache , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com Subject: Re: [PATCH v11 00/15] khugepaged: mTHP support Message-ID: References: <20250912032810.197475-1-npache@redhat.com> <20250912133701.GA802874@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: t1y6ketpbrpojbhmkdj6t6b8m8rq8k1a X-Rspam-User: X-Rspamd-Queue-Id: 6528D1C0007 X-Rspamd-Server: rspam04 X-HE-Tag: 1757691864-846839 X-HE-Meta: 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 O6V5Ka5s E3t4e0+0m3eM3T+opMXJsA+J4WS8kjiPl92k2IotRrfMZTrF/4lAMFrsIdY7PpW+VAJJPuJWMN0iDfSN8Nst0L6hF9ehMZ5x23u0+odi0iI5jDJFvlSsFypcirZOsIFnGY/OK+7h/90dBDD4GLgdGpA+mlhtnSNzkqwCiZR1yFYDTo7g4WKjG77gdepoEMFqVI53dcFOzkIPj+Jat6NqIurcsSsZavoFQtqdMrSpQZDkYU8iUElG9HI8qTvO1M92eUtE5/H+En/uqHbfgH92ymRC+WPT5ZmwrVN8X71qeTlrxpT15offBCOXkkGCAR/7jsjqIAjA09B3qEZI= 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, Sep 12, 2025 at 04:39:02PM +0100, Kiryl Shutsemau wrote: > > Shower thought: it might be in these cases especially where the FreeBSD > > reservation system comes in handy - best effort allocating a THP, but not > > actually mapping it as such until you really _know_ it is hot - and until > > then, memory reclaim can just break your THP down if it really needs to. > > This is just silly. All downsides without benefit until maybe later. And > for short-lived processes the "later" never comes. The right way out is to get better info on access pattern from hardware. For instance, if we move access bit out of page table entry and make it independent of the actually mapping size that would give us much better view on what actually is going on. -- Kiryl Shutsemau / Kirill A. Shutemov