From 887e97745ec336c2f49b6c0af3c4cc00a5df3211 Mon Sep 17 00:00:00 2001 From: Mateusz Guzik Date: Wed, 3 Dec 2025 10:48:37 +0100 Subject: fs: track the inode having file locks with a flag in ->i_opflags 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 Signed-off-by: Mateusz Guzik Link: https://patch.msgid.link/20251203094837.290654-2-mjguzik@gmail.com Signed-off-by: Christian Brauner --- include/linux/fs.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/fs.h') diff --git a/include/linux/fs.h b/include/linux/fs.h index 04ceeca12a0d..094b0adcb035 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -631,6 +631,7 @@ is_uncached_acl(struct posix_acl *acl) #define IOP_MGTIME 0x0020 #define IOP_CACHED_LINK 0x0040 #define IOP_FASTPERM_MAY_EXEC 0x0080 +#define IOP_FLCTX 0x0100 /* * Inode state bits. Protected by inode->i_lock -- cgit v1.2.3