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[2001:678:a5c:1202:4fb5:f16a:579c:6dcb]) by smtp.gmail.com with UTF8SMTPSA id 2adb3069b0e04-553ac11680fsm777892e87.5.2025.06.14.04.25.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Jun 2025 04:25:27 -0700 (PDT) Date: Sat, 14 Jun 2025 13:25:27 +0200 From: Klara Modin To: Nico Pache Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, rientjes@google.com, hannes@cmpxchg.org, lorenzo.stoakes@oracle.com, rdunlap@infradead.org, mhocko@suse.com, Liam.Howlett@oracle.com, zokeefe@google.com, surenb@google.com, jglisse@google.com, cl@gentwo.org, jack@suse.cz, dave.hansen@linux.intel.com, will@kernel.org, tiwai@suse.de, catalin.marinas@arm.com, anshuman.khandual@arm.com, dev.jain@arm.com, raquini@redhat.com, aarcange@redhat.com, kirill.shutemov@linux.intel.com, yang@os.amperecomputing.com, thomas.hellstrom@linux.intel.com, vishal.moola@gmail.com, sunnanyong@huawei.com, usamaarif642@gmail.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, shuah@kernel.org, peterx@redhat.com, willy@infradead.org, ryan.roberts@arm.com, baolin.wang@linux.alibaba.com, baohua@kernel.org, david@redhat.com, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, rostedt@goodmis.org, corbet@lwn.net, akpm@linux-foundation.org Subject: Re: [PATCH v6 1/4] mm: defer THP insertion to khugepaged Message-ID: References: <20250515033857.132535-1-npache@redhat.com> <20250515033857.132535-2-npache@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250515033857.132535-2-npache@redhat.com> X-Rspamd-Queue-Id: 92AD540008 X-Rspamd-Server: rspam07 X-Stat-Signature: yci4mb1zprj7axcmfme5mmkd8gytb9mq X-Rspam-User: X-HE-Tag: 1749900330-890590 X-HE-Meta: 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 t6tzNhaZ CAnLb7TMRHrST/xxroKGwSNhPuMqbKoQ1ifx+pdcO2V2t9a0F11GdsYLMKgTPdAA1JSsLCAufqZP8a2LRDkAWPKTvbw== 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: Hi, On 2025-05-14 21:38:54 -0600, Nico Pache wrote: > setting /transparent_hugepages/enabled=always allows applications > to benefit from THPs without having to madvise. However, the page fault > 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. > > Acked-by: Zi Yan > Co-developed-by: Rafael Aquini > Signed-off-by: Rafael Aquini > Signed-off-by: Nico Pache ... > @@ -315,13 +318,20 @@ static ssize_t enabled_store(struct kobject *kobj, > > if (sysfs_streq(buf, "always")) { > clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparent_hugepage_flags); > set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > + } else if (sysfs_streq(buf, "defer")) { > + clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > + set_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparent_hugepage_flags); > } else if (sysfs_streq(buf, "madvise")) { > clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparent_hugepage_flags); > set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > } else if (sysfs_streq(buf, "never")) { > clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparent_hugepage_flags); > } else > ret = -EINVAL; > > @@ -954,18 +964,31 @@ static int __init setup_transparent_hugepage(char *str) > &transparent_hugepage_flags); > clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, > + &transparent_hugepage_flags); > ret = 1; > + } else if (!strcmp(str, "defer")) { > + clear_bit(TRANSPARENT_HUGEPAGE_FLAG, > + &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > + &transparent_hugepage_flags); > + set_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, > + &transparent_hugepage_flags); There should probably be a corresponding ret = 1; here. Otherwise the cannot parse message will displayed even if defer was set. > } else if (!strcmp(str, "madvise")) { > clear_bit(TRANSPARENT_HUGEPAGE_FLAG, > &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, > + &transparent_hugepage_flags); > set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > - &transparent_hugepage_flags); > + &transparent_hugepage_flags); > ret = 1; > } else if (!strcmp(str, "never")) { > clear_bit(TRANSPARENT_HUGEPAGE_FLAG, > &transparent_hugepage_flags); > clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, > + &transparent_hugepage_flags); > ret = 1; > } > out: > -- > 2.49.0 > Regards, Klara Modin