From: menglong8.dong@gmail.com
To: bhelgaas@google.com
Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
Menglong Dong <imagedong@tencent.com>
Subject: [PATCH] pci: call _cond_resched() after pci_bus_write_config
Date: Wed, 13 Oct 2021 20:55:42 +0800 [thread overview]
Message-ID: <20211013125542.759696-1-imagedong@tencent.com> (raw)
From: Menglong Dong <imagedong@tencent.com>
While the system is running in KVM, pci config writing for virtio devices
may cost long time(about 1-2ms), as it causes VM-exit. During
__pci_bus_assign_resources(), pci_setup_bridge, which can do pci config
writing up to 10 times, can be called many times without any
_cond_resched(). So __pci_bus_assign_resources can cause 25+ms scheduling
latency with !CONFIG_PREEMPT.
To solve this problem, call _cond_resched() after pci config writing.
Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
drivers/pci/access.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 46935695cfb9..babed43702df 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -57,6 +57,7 @@ int noinline pci_bus_write_config_##size \
pci_lock_config(flags); \
res = bus->ops->write(bus, devfn, pos, len, value); \
pci_unlock_config(flags); \
+ _cond_resched(); \
return res; \
}
--
2.27.0
next reply other threads:[~2021-10-13 12:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-13 12:55 menglong8.dong [this message]
2021-10-13 19:00 ` [PATCH] pci: call _cond_resched() after pci_bus_write_config Bjorn Helgaas
2021-10-14 2:34 ` Menglong Dong
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