Messages in this thread Patch in this message | | | From | Jiang Biao <> | Subject | [PATCH] driver/pci: reduce the single block time in pci_read_config | Date | Mon, 24 Aug 2020 13:20:25 +0800 |
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From: Jiang Biao <benbjiang@tencent.com>
pci_read_config() could block several ms in kernel space, mainly caused by the while loop to call pci_user_read_config_dword(). Singel pci_user_read_config_dword() loop could consume 130us+, | pci_user_read_config_dword() { | _raw_spin_lock_irq() { ! 136.698 us | native_queued_spin_lock_slowpath(); ! 137.582 us | } | pci_read() { | raw_pci_read() { | pci_conf1_read() { 0.230 us | _raw_spin_lock_irqsave(); 0.035 us | _raw_spin_unlock_irqrestore(); 8.476 us | } 8.790 us | } 9.091 us | } ! 147.263 us | } and dozens of the loop could consume ms+.
If we execute some lspci commands concurrently, ms+ scheduling latency could be detected.
Add scheduling chance in the loop to improve the latency.
Reported-by: Bin Lai <robinlai@tencent.com> Signed-off-by: Jiang Biao <benbjiang@tencent.com> --- drivers/pci/pci-sysfs.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 6d78df9..3b9f63d 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -708,6 +708,7 @@ static ssize_t pci_read_config(struct file *filp, struct kobject *kobj, data[off - init_off + 3] = (val >> 24) & 0xff; off += 4; size -= 4; + cond_resched(); } if (size >= 2) { -- 1.8.3.1
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