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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1q9qcD-007tr1-7Z; Thu, 15 Jun 2023 17:18:33 +0000 Date: Thu, 15 Jun 2023 18:18:33 +0100 From: Matthew Wilcox To: James Houghton Cc: Michal Hocko , Mike Kravetz , David Rientjes , linux-mm@kvack.org, David Hildenbrand , John Hubbard , Peter Xu , Vlastimil Babka , Zi Yan Subject: Re: [Invitation] Linux MM Alignment Session on HugeTLB Core MM Convergence on Wednesday Message-ID: References: <20230614230458.GB3559@monkey> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 470EE1C0021 X-Stat-Signature: xstdsxfg1spbtfka74qyynfref5phbzm X-Rspam-User: X-HE-Tag: 1686849519-909264 X-HE-Meta: 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 jijKYDf6 LY3+emZNZ9PVmT19EXZvbU3W9+Lq3jwexRX/hPevJR8vQlngUYsa+r/0v0ywPzFo2Dye9D7lI4rfgddk8YQhh8xrBhLveRkD3LL4MSJMBSUzfT0iwDp1Rb+mSjlkn4Uc8gvi2z+qMROmdSMlCh4cqA2DifvJo3R0saHm3 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: On Thu, Jun 15, 2023 at 10:00:41AM -0700, James Houghton wrote: > I can't speak in detail about how databases recover from memory > poison. Mike, maybe you can share more details? Speaking generally (this would describe MySQL as well as any number of proprietary databases), hugetlbfs is used by databases as a supplier of memory to their userspace buffer cache. As database blocks are needed, they're read from storage using O_DIRECT. Depending on the database, they may or may not be updated in place. Just as in our page cache, if the hwpoison hits in a clean block, it can discard the block and re-read it. If it hits in a dirty block, it's Game Over. Most blocks are clean. A 1GB page contains so many blocks that taking out the entire 1GB is guaranteed to take out a dirty block. Taking out a single 4kB page is likely to take out only clean blocks.