Re: [PATCH] Fixes: 496d0a648509 ("cpuidle: Fix guest_halt_poll_ns failed to take effect when setting guest_halt_poll_allow_shrink=N")

Why did you put a Fixes; tag in the subject?

Please provide a proper subject and put the Fixes: tag next to the Signed-off-by: one below.

On Mon, Aug 26, 2024 at 11:07 AM Yanhao Dong 570260087@qq.com wrote:

From: ysay ysaydong@gmail.com

When guest_halt_poll_allow_shrink=N,setting guest_halt_poll_ns from a large value to 0 does not reset the CPU polling time, despite guest_halt_poll_ns being intended as a mandatory maximum time limit.

The problem was situated in the adjust_poll_limit() within drivers/cpuidle/governors/haltpoll.c:79.

Specifically, when guest_halt_poll_allow_shrink was set to N, resetting guest_halt_poll_ns to zero did not lead to executing any section of code that adjusts dev->poll_limit_ns.

The issue has been resolved by relocating the check and assignment for dev->poll_limit_ns outside of the conditional block. This ensures that every modification to guest_halt_poll_ns properly influences the CPU polling time.

Signed-off-by: ysay ysaydong@gmail.com

drivers/cpuidle/governors/haltpoll.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c index 663b7f164..99c6260d7 100644 --- a/drivers/cpuidle/governors/haltpoll.c +++ b/drivers/cpuidle/governors/haltpoll.c @@ -78,26 +78,22 @@ static int haltpoll_select(struct cpuidle_driver *drv,

static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns) {

•   unsigned int val;
  

•   unsigned int val = dev->poll_limit_ns;
  
    /* Grow cpu_halt_poll_us if
     * cpu_halt_poll_us < block_ns < guest_halt_poll_us
     */
    if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) {
  

•           val = dev->poll_limit_ns * guest_halt_poll_grow;
  

•           val *= guest_halt_poll_grow;
  
            if (val < guest_halt_poll_grow_start)
                    val = guest_halt_poll_grow_start;
  

•           if (val > guest_halt_poll_ns)
  

•                   val = guest_halt_poll_ns;
  
            trace_guest_halt_poll_ns_grow(val, dev->poll_limit_ns);
  

•           dev->poll_limit_ns = val;
    } else if (block_ns > guest_halt_poll_ns &&
               guest_halt_poll_allow_shrink) {
            unsigned int shrink = guest_halt_poll_shrink;
  
  

•           val = dev->poll_limit_ns;
            if (shrink == 0) {
                    val = 0;
            } else {
  

@@ -108,8 +104,12 @@ static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns) }

            trace_guest_halt_poll_ns_shrink(val, dev->poll_limit_ns);

•           dev->poll_limit_ns = val;
    }
  

•   if (val > guest_halt_poll_ns)
  

•           val = guest_halt_poll_ns;
  

•   dev->poll_limit_ns = val;
  

}

/**

2.43.5