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Peter Anvin" , "Yin, Fengwei" , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 18/18] arm64/mm: Automatically fold contpte mappings Message-ID: References: <20240215103205.2607016-1-ryan.roberts@arm.com> <20240215103205.2607016-19-ryan.roberts@arm.com> <1285eb59-fcc3-4db8-9dd9-e7c4d82b1be0@huawei.com> <8d57ed0d-fdd0-4fc6-b9f1-a6ac11ce93ce@arm.com> <018b5e83-789e-480f-82c8-a64515cdd14a@huawei.com> <43a5986a-52ea-4090-9333-90af137a4735@linux.alibaba.com> <306874fe-9bc1-4dec-a856-0125e4541971@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <306874fe-9bc1-4dec-a856-0125e4541971@arm.com> X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: A357DC0015 X-Stat-Signature: brr1hfehpe7cpf8i1a48zf486fi1z1wx X-HE-Tag: 1719320818-933467 X-HE-Meta: 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 wSvnGM0q +YWs1QqYFFDE0Qvd4ykELJO5ofv5Gr5fl1yztgEf+tkdIxSFYrHxDB7mbwUMcuqhW7B0DH2gPci9M0gq7zciJA4XCHZFupHiE6kvJrL/aIHLAzOa2cdgD8CvBs2X0tn71rirpKSf7nRVvQOjhF8YHiZyUu/xVqnnWu1seqRQXBZofTxeS31dZLPeytLih+oeL5V1LlWkzE/VdNiRvGuIWAlUiJ1dvjqKzOUJa99ZyrIvwj3uVfZ7gYRxSK8A15xSxsRxJLbTegmbIwVaKXU4tUui9cQ== 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 Tue, Jun 25, 2024 at 01:41:02PM +0100, Ryan Roberts wrote: > On 25/06/2024 13:37, Baolin Wang wrote: > > [...] > > >>> For other filesystems, like ext4, I did not found the logic to determin what > >>> size of folio to allocate in writable mmap() path > >> > >> Yes I'd be keen to understand this to. When I was doing contpte, page cache > >> would only allocate large folios for readahead. So that's why I wouldn't have > > > > You mean non-large folios, right? > > No I mean that at the time I wrote contpte, the policy was to allocate an > order-0 folio for any writes that missed in the page cache, and allocate large > folios only when doing readahead from storage into page cache. The test that is > regressing is doing writes. mmap() faults also use readahead. filemap_fault(): folio = filemap_get_folio(mapping, index); if (likely(!IS_ERR(folio))) { if (!(vmf->flags & FAULT_FLAG_TRIED)) fpin = do_async_mmap_readahead(vmf, folio); which does: if (folio_test_readahead(folio)) { fpin = maybe_unlock_mmap_for_io(vmf, fpin); page_cache_async_ra(&ractl, folio, ra->ra_pages); which has been there in one form or another since 2007 (3ea89ee86a82).