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([2620:10d:c092:500::7:6466]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5e05168c467sm2448555a12.48.2025.02.17.06.59.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Feb 2025 06:59:03 -0800 (PST) Message-ID: Date: Mon, 17 Feb 2025 14:59:02 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v2 1/5] mm: defer THP insertion to khugepaged To: Nico Pache , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Cc: ryan.roberts@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, srivatsa@csail.mit.edu, haowenchao22@gmail.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, jglisse@google.com, surenb@google.com, vishal.moola@gmail.com, zokeefe@google.com, zhengqi.arch@bytedance.com, jhubbard@nvidia.com, 21cnbao@gmail.com, willy@infradead.org, kirill.shutemov@linux.intel.com, david@redhat.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.com, sunnanyong@huawei.com, audra@redhat.com, akpm@linux-foundation.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, tiwai@suse.de, baolin.wang@linux.alibaba.com, corbet@lwn.net, shuah@kernel.org References: <20250211004054.222931-1-npache@redhat.com> <20250211004054.222931-2-npache@redhat.com> Content-Language: en-US From: Usama Arif In-Reply-To: <20250211004054.222931-2-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/02/2025 00:40, Nico Pache wrote: > setting /transparent_hugepages/enabled=always allows applications > to benefit from THPs without having to madvise. However, the pf handler > takes very few considerations to decide weather or not to actually use a > THP. This can lead to a lot of wasted memory. khugepaged only operates > on memory that was either allocated with enabled=always or MADV_HUGEPAGE. > > Introduce the ability to set enabled=defer, which will prevent THPs from > being allocated by the page fault handler unless madvise is set, > leaving it up to khugepaged to decide which allocations will collapse to a > THP. This should allow applications to benefits from THPs, while curbing > some of the memory waste. > > Signed-off-by: Nico Pache > --- > include/linux/huge_mm.h | 15 +++++++++++++-- > mm/huge_memory.c | 31 +++++++++++++++++++++++++++---- > 2 files changed, 40 insertions(+), 6 deletions(-) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 93e509b6c00e..fb381ca720ea 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -44,6 +44,7 @@ enum transparent_hugepage_flag { > TRANSPARENT_HUGEPAGE_UNSUPPORTED, > TRANSPARENT_HUGEPAGE_FLAG, > TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > + TRANSPARENT_HUGEPAGE_DEFER_PF_INST_FLAG, No strong preference, but maybe just TRANSPARENT_HUGEPAGE_DEFER_FLAG might be better?