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Howlett" , Jens Axboe , linux-kernel@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org, Ritesh Harjani , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Darrick J . Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav Subject: Re: [PATCH v2 3/5] mm: add persistent huge zero folio Message-ID: References: <20250808121141.624469-1-kernel@pankajraghav.com> <20250808121141.624469-4-kernel@pankajraghav.com> <731d8b44-1a45-40bc-a274-8f39a7ae0f7f@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <731d8b44-1a45-40bc-a274-8f39a7ae0f7f@lucifer.local> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4F4A41C0004 X-Stat-Signature: zi7oidway77is5g8opkym34pxmjqxyue X-HE-Tag: 1754901223-440021 X-HE-Meta: U2FsdGVkX1+8xv7txtUbCRQtxVZcdo4iXdOhsRfaNSxjaMQXAgKaUW8DbixrU1y3bsxTLCOd72w/6iR6TCxTg7V81U+t8Be3uE+uDa6ZIFSBozOJkmqddrVzi/k8TqQBsE+sz1phyMr5SgqwXJX+McDU9rlqN3MZx6lhp0GHeFnh77JS7SY2+Xyxm/kXH8E5w8Ph+aNW/dIT3MYzapf689k+kUvIJAAQMTgnLoo+GttwosWLMbGAbC2Mr1B7ch+ZMDpkL5lAw9FOJwtEbdAVuov/FdLzOhMi5rmSypONsUwlYPvZv/VVZeVA8pupS408hlZV3JWe4Yi6b4u31clBEQHC5ueDZux0V+J6mEUEUGQkgjkQOlgeerAMIF7G7p3gGVptnn+vBCVUkgq6hH1Kkakqc5NXHmdb5SRu7zdzylKtAnsE/DoC64cILMUFy4Vg8AFdySzIVEaQVIDHUoH2JZpIkhj53B1d4BIwS1Ly01KcOw5J5Zfy2SYUKAFRszoLR66jjlEwlTK+3FI5u4GBBH1ix7MECaFJ6G+adnOZL7EqRmq5Wib23pGLUDzwNY8Zas2jt9I/UhwSyuvRLuWTKxCd8dGfthzVlvgL12Gz1pyOz0ev+a+v/BT2JahB/XKLoYOAl8SiT77KnSsASpa7ncxtMxWoxqJap9Lck3ikiANRT3H6nnupVLC0n6Bs20SfdD/ugWCIziI4EZrlWNBy1Hxr3XkGBn35bXyqBzGCERFXBETEWT4ZoNSCMuFmltIEfW3SJB3+5Rrhdd05vezXjC/KfSAkRqgGN4Ph6ba9W2vXI+W1+W3aNL2B1nIaOe4OyakJRvQnwJBv84wDArWCK3iC6n9eR7B9k4dILOgUQ3Jp5M4RhovFF23qS1SptlfdvAclgeTLj73fawMarMZTINdu/N/Qp06s6RnM0M4Ouby1TdWRLZu0fsTQo15gyPefKVw+G6XdpikCeCqC1l0 RHZkICDj uP4PEp/CnoYobBo5qJW1f5IVY3PkRBKWY9pgpjjdIkYqPI2QdH9+USEKHc9t+KDih4BOxuG61ye15tGFPJulSOJIx8spR673ukIgm/qJKmTb4A3WX5eGDvUvB5Lwhhc1Do9xJXwDxOvmmAWrcT1pWePWR/XG2txY0FHPkgXIefFd5OpMl14TIwVvJ9V+KZxJvl23ulWurM3TE/X1ePwy5gutkrIM1/a+ry9CuVMzxKNwJE4IeORCQ6DbYbNtrtH2zSKQZqAH997C9L4j2g+4ntOoorMTZpi49kyZcWwgFIrqo3SUqt1Uc1y1n1sEU5yLsWEohu1LOmh8OXGxjCTB5ZhOu0Lj3hIs3hlAQLxfwvoRSsDg= 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: > This is much nicer and now _super_ simple, I like it. Thanks to you and David :) > > A few nits below but generally: > > Reviewed-by: Lorenzo Stoakes Thanks. > > > --- > > include/linux/huge_mm.h | 16 ++++++++++++++++ > > mm/Kconfig | 16 ++++++++++++++++ > > mm/huge_memory.c | 40 ++++++++++++++++++++++++++++++---------- > > 3 files changed, 62 insertions(+), 10 deletions(-) > > > > static inline int split_folio_to_list_to_order(struct folio *folio, > > diff --git a/mm/Kconfig b/mm/Kconfig > > index e443fe8cd6cf..fbe86ef97fd0 100644 > > --- a/mm/Kconfig > > +++ b/mm/Kconfig > > @@ -823,6 +823,22 @@ config ARCH_WANT_GENERAL_HUGETLB > > config ARCH_WANTS_THP_SWAP > > def_bool n > > > > +config PERSISTENT_HUGE_ZERO_FOLIO > > + bool "Allocate a PMD sized folio for zeroing" > > + depends on TRANSPARENT_HUGEPAGE > > I feel like we really need to sort out what is/isn't predicated on THP... it > seems like THP is sort of short hand for 'any large folio stuff' but not > always... > > But this is a more general point :) I already brought this topic once during THP cabal. I am thinking of submitting a talk about this topic for LPC Memory Management MC. > > > + help > > + Enable this option to reduce the runtime refcounting overhead > > + of the huge zero folio and expand the places in the kernel > > + that can use huge zero folios. This can potentially improve > > + the performance while performing an I/O. > > NIT: I think we can drop 'an', and probably refactor this sentence to something > like 'For instance, block I/O benefits from access to large folios for zeroing > memory'. > > > + > > + With this option enabled, the huge zero folio is allocated > > + once and never freed. One full huge page worth of memory shall > > + be used. > > NIT: huge page worth -> huge page's worth > Thanks for the comments. I will make those changes and send a new version. -- Pankaj