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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1t93zW-00000006qn1-0mvG; Thu, 07 Nov 2024 15:00:10 +0000 Date: Thu, 7 Nov 2024 15:00:09 +0000 From: Matthew Wilcox To: Yafang Shao Cc: akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/readahead: Fix large folio support in async readahead Message-ID: References: <20241106092114.8408-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam10 X-Stat-Signature: b9gkaom1ji5nod5naj1f1f4nr1goy8ka X-Rspamd-Queue-Id: 424B740016 X-Rspam-User: X-HE-Tag: 1730991576-52904 X-HE-Meta: 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 7i9J1iwZ tvYtea5dvWApzhH10yY6g9NmqlsO/1BD5ptl+xFuAZQvdJdOckrz+hNOZZ3M3pNq0ymDFcjAAlYqYZpxuPUv3XBR4MEz9oyThjYaWLfasWO4HUSyC4K6Dz+47mVjebYEeumZUDq2QrcdX6uE4AcoXtYxwN4S+6qUX0J0YrvSHX+mMKVJk2t9Z2DR3e4VEKfwAmFD1ctHnSqHvfoAYaWvmMEpceGv3bMmMq1XJTzAy5EvoHONeqP+hBq1bav2GU+asi2tp 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 Thu, Nov 07, 2024 at 01:55:52PM +0800, Yafang Shao wrote: > > Let's suppose that someone sets read_ahead_kb to 192kB. If the previous > > readahead did 128kB, we now try to align that to 128kB, so we'll readahead > > 256kB which is larger than max. We were only intending to breach the > > 'max' for the MADV_HUGE case, not for all cases. > > In the non-MADV_HUGE case, the order can only be 0, correct? No. The readahead code will use larger orders, depending on the size of reads and how successful readahead is performing.