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From: Dave Hansen <dave.hansen@intel.com>
To: Yaohui Wang <yaohuiwang@linux.alibaba.com>, tglx@linutronix.de
Cc: luto@kernel.org, peterz@infradead.org, mingo@redhat.com,
	bp@alien8.de, x86@kernel.org, linux-kernel@vger.kernel.org,
	luoben@linux.alibaba.com, Tom Lendacky <thomas.lendacky@amd.com>,
	Brijesh Singh <brijesh.singh@amd.com>
Subject: Re: [PATCH v3 1/2] x86/ioremap: fix the pfn calculation mistake in __ioremap_check_ram()
Date: Fri, 2 Jul 2021 07:49:01 -0700	[thread overview]
Message-ID: <663229c2-1957-2af5-678c-5d553507f5f3@intel.com> (raw)
In-Reply-To: <34bae667-180f-ce97-ee55-12e13ff28ca0@linux.alibaba.com>

On 7/2/21 3:05 AM, Yaohui Wang wrote:
> On 2021/7/1 22:41, Dave Hansen wrote:
>> Was this issue found by inspection, or is it causing an actual problem
>> in practice?
> 
> This issus truly caused terrible perforamnce downgrade in the practice.
> When developing an out of tree module in our testing environment,
> invoking ioremap() on normal RAM causes apparent CLI lag. The Unixbench
> score also decreases a lot (5x slowdown in the worst case).
> 
> Debugging such performance issue is extremely difficult, especially when
> the code of the faulty module itself is already very complex. I tested
> the system in many aspects before finally located this problem.

Do you know why this check:

> 	if ((res->flags & IORESOURCE_SYSTEM_RAM) != IORESOURCE_SYSTEM_RAM)
> 		return false;

did not catch your out-of-tree driver's errant ioremap()?

  reply	other threads:[~2021-07-02 14:49 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-21 12:34 [PATCH v3 0/2] x86/ioremap: fix boundary calculation and boundary judgment issues for ioremap() Yaohui Wang
2021-06-21 12:34 ` [PATCH v3 1/2] x86/ioremap: fix the pfn calculation mistake in __ioremap_check_ram() Yaohui Wang
2021-07-01 14:41   ` Dave Hansen
2021-07-02 10:05     ` Yaohui Wang
2021-07-02 14:49       ` Dave Hansen [this message]
2021-07-05  2:11         ` Yaohui Wang
2021-06-21 12:34 ` [PATCH v3 2/2] kernel/resource: fix boundary judgment issues in find_next_iomem_res() and __walk_iomem_res_desc() Yaohui Wang
2021-07-01 16:29   ` Dave Hansen
2021-07-01  2:44 ` [PATCH v3 0/2] x86/ioremap: fix boundary calculation and boundary judgment issues for ioremap() Yaohui Wang

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