[PATCH OLK-6.6 0/1] Backport fs optimizing patch from mainline
64 bits in open_fds are mapped to a common bit in full_fds_bits. It is very likely that a bit in full_fds_bits has been cleared before in __clear_open_fds()'s operation. Check the clear bit in full_fds_bits before clearing to avoid unnecessary write and cache bouncing. See commit fc90888d07b8 ("vfs: conditionally clear close-on-exec flag") for a similar optimization. take stock kernel with patch 1 as baseline, it improves pts/blogbench-1.1.0 read for 13%, and write for 5% on Intel ICX 160 cores configuration with v6.10-rc7. Yu Ma (1): fs/file.c: conditionally clear full_fds fs/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) -- 2.20.1
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From: Yu Ma <yu.ma@intel.com> mainline inclusion from mainline-v6.12-rc3 commit c9a3019603b8a8519f1b6d8ae0059bcb2965f8fe category: performance bugzilla: https://gitee.com/openeuler/kernel/issues/IB8ROX CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ------------------------------------------------- 64 bits in open_fds are mapped to a common bit in full_fds_bits. It is very likely that a bit in full_fds_bits has been cleared before in __clear_open_fds()'s operation. Check the clear bit in full_fds_bits before clearing to avoid unnecessary write and cache bouncing. See commit fc90888d07b8 ("vfs: conditionally clear close-on-exec flag") for a similar optimization. take stock kernel with patch 1 as baseline, it improves pts/blogbench-1.1.0 read for 13%, and write for 5% on Intel ICX 160 cores configuration with v6.10-rc7. Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Yu Ma <yu.ma@intel.com> Link: https://lore.kernel.org/r/20240717145018.3972922-3-yu.ma@intel.com Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- fs/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/file.c b/fs/file.c index f8a5af0d06f1..b5780c9e0098 100644 --- a/fs/file.c +++ b/fs/file.c @@ -265,7 +265,9 @@ static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt) static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt) { __clear_bit(fd, fdt->open_fds); - __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits); + fd /= BITS_PER_LONG; + if (test_bit(fd, fdt->full_fds_bits)) + __clear_bit(fd, fdt->full_fds_bits); } /* -- 2.20.1
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