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887e97745e
Opening and closing an inode dirties the ->i_readcount field. Depending on the alignment of the inode, it may happen to false-share with other fields loaded both for both operations to various extent. This notably concerns the ->i_flctx field. Since most inodes don't have the field populated, this bit can be managed with a flag in ->i_opflags instead which bypasses the problem. Here are results I obtained while opening a file read-only in a loop with 24 cores doing the work on Sapphire Rapids. Utilizing the flag as opposed to reading ->i_flctx field was toggled at runtime as the benchmark was running, to make sure both results come from the same alignment. before: 3233740 after: 3373346 (+4%) before: 3284313 after: 3518711 (+7%) before: 3505545 after: 4092806 (+16%) Or to put it differently, this varies wildly depending on how (un)lucky you get. The primary bottleneck before and after is the avoidable lockref trip in do_dentry_open(). Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Link: https://patch.msgid.link/20251203094837.290654-2-mjguzik@gmail.com Signed-off-by: Christian Brauner <brauner@kernel.org>