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| author | Thomas Gleixner <tglx@linutronix.de> | 2019-11-12 01:03:22 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-11-16 13:24:02 +0300 |
| commit | 060aa16fdb7c5078a4159a76e5dc87d6a493af9b (patch) | |
| tree | 63f2ffbc60ce9e1064ca13bc128efeb7c1e7f6c8 /arch/x86/kernel/cpu/common.c | |
| parent | 577d5cd7e5851d3832066cd0422475fa7db2ee17 (diff) | |
| download | linux-060aa16fdb7c5078a4159a76e5dc87d6a493af9b.tar.xz | |
x86/ioperm: Add bitmap sequence number
Add a globally unique sequence number which is incremented when ioperm() is
changing the I/O bitmap of a task. Store the new sequence number in the
io_bitmap structure and compare it with the sequence number of the I/O
bitmap which was last loaded on a CPU. Only update the bitmap if the
sequence is different.
That should further reduce the overhead of I/O bitmap scheduling when there
are only a few I/O bitmap users on the system.
The 64bit sequence counter is sufficient. A wraparound of the sequence
counter assuming an ioperm() call every nanosecond would require about 584
years of uptime.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 3aee167246f7..79dd544bb974 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1862,6 +1862,7 @@ void cpu_init(void) tss_setup_ist(tss); tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID; tss->io_bitmap.prev_max = 0; + tss->io_bitmap.prev_sequence = 0; memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap)); set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss); |