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Tue, 17 Jun 2025 10:52:53 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHsuDUpqbT4Zm+fDNYLZyRvnIomvlXs1lgyYMEYTlPSDFNwpQpbOwB39H6AdaylUKoeEGHtBp3S/5ilov+jo+Q= X-Received: by 2002:a05:690c:9a07:b0:703:b3b8:1ca1 with SMTP id 00721157ae682-7117536e5f3mr174053697b3.5.1750182773635; Tue, 17 Jun 2025 10:52:53 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250515033857.132535-1-npache@redhat.com> <20250515033857.132535-2-npache@redhat.com> In-Reply-To: From: Nico Pache Date: Tue, 17 Jun 2025 11:52:26 -0600 X-Gm-Features: AX0GCFswQblbC-fUl4LgnBDpA9J_EkZ2hl0iyVshZHwGMIbdVVRH-b1apF1auqA Message-ID: Subject: Re: [PATCH v6 1/4] mm: defer THP insertion to khugepaged To: Klara Modin 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sat, Jun 14, 2025 at 5:25=E2=80=AFAM Klara Modin = wrote: > > Hi, > > On 2025-05-14 21:38:54 -0600, Nico Pache wrote: > > setting /transparent_hugepages/enabled=3Dalways 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 actua= lly > > use a THP. This can lead to a lot of wasted memory. khugepaged only > > operates on memory that was either allocated with enabled=3Dalways or > > MADV_HUGEPAGE. > > > > Introduce the ability to set enabled=3Ddefer, which will prevent THPs f= rom > > being allocated by the page fault handler unless madvise is set, > > leaving it up to khugepaged to decide which allocations will collapse t= o a > > THP. This should allow applications to benefits from THPs, while curbin= g > > 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, &transparen= t_hugepage_flags); > > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparen= t_hugepage_flags); > > set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_= flags); > > + } else if (sysfs_streq(buf, "defer")) { > > + clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepag= e_flags); > > + clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparen= t_hugepage_flags); > > + set_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparent_= hugepage_flags); > > } else if (sysfs_streq(buf, "madvise")) { > > clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepag= e_flags); > > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparen= t_hugepage_flags); > > set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_= hugepage_flags); > > } else if (sysfs_streq(buf, "never")) { > > clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepag= e_flags); > > clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparen= t_hugepage_flags); > > + clear_bit(TRANSPARENT_HUGEPAGE_DEFER_PF_FLAG, &transparen= t_hugepage_flags); > > } else > > ret =3D -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 =3D 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 =3D 1; > here. Otherwise the cannot parse message will displayed even if defer > was set. Thanks Klara-- I will make sure to add it on the next version! > > > } 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 =3D 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 =3D 1; > > } > > out: > > -- > > 2.49.0 > > > > Regards, > Klara Modin >