From: Robert Richter <robert.richter@cavium.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Hanjun Guo <hanjun.guo@linaro.org>,
Yisheng Xie <xieyisheng1@huawei.com>,
James Morse <james.morse@arm.com>
Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Thu, 5 Jan 2017 12:24:07 +0100 [thread overview]
Message-ID: <20170105112407.GU4930@rric.localdomain> (raw)
In-Reply-To: <20170104140223.GF18193@arm.com>
On 04.01.17 14:02:23, Will Deacon wrote:
> Using early_pfn_valid feels like a bodge to me, since having pfn_valid
> return false for something that early_pfn_valid says is valid (and is
> therefore initialised in the memmap) makes the NOMAP semantics even more
> confusing.
The concern I have had with HOLES_IN_ZONE is that it enables
pfn_valid_within() for arm64. This means that each pfn of a section is
checked which is done only once for the section otherwise. With up to
2^18 pages per section we traverse the memblock list by that factor
more often. There could be a performance regression. I haven't numbers
yet, since the fix causes another kernel crash. And, this is the next
problem I have. The crash doesn't happen otherwise. So, either it
uncovers another bug or the fix is incomplete. Though the changes look
like it should work. This needs more investigation.
-Robert
WARNING: multiple messages have this Message-ID (diff)
From: Robert Richter <robert.richter@cavium.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Hanjun Guo <hanjun.guo@linaro.org>,
Yisheng Xie <xieyisheng1@huawei.com>,
James Morse <james.morse@arm.com>
Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Thu, 5 Jan 2017 12:24:07 +0100 [thread overview]
Message-ID: <20170105112407.GU4930@rric.localdomain> (raw)
In-Reply-To: <20170104140223.GF18193@arm.com>
On 04.01.17 14:02:23, Will Deacon wrote:
> Using early_pfn_valid feels like a bodge to me, since having pfn_valid
> return false for something that early_pfn_valid says is valid (and is
> therefore initialised in the memmap) makes the NOMAP semantics even more
> confusing.
The concern I have had with HOLES_IN_ZONE is that it enables
pfn_valid_within() for arm64. This means that each pfn of a section is
checked which is done only once for the section otherwise. With up to
2^18 pages per section we traverse the memblock list by that factor
more often. There could be a performance regression. I haven't numbers
yet, since the fix causes another kernel crash. And, this is the next
problem I have. The crash doesn't happen otherwise. So, either it
uncovers another bug or the fix is incomplete. Though the changes look
like it should work. This needs more investigation.
-Robert
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WARNING: multiple messages have this Message-ID (diff)
From: robert.richter@cavium.com (Robert Richter)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Thu, 5 Jan 2017 12:24:07 +0100 [thread overview]
Message-ID: <20170105112407.GU4930@rric.localdomain> (raw)
In-Reply-To: <20170104140223.GF18193@arm.com>
On 04.01.17 14:02:23, Will Deacon wrote:
> Using early_pfn_valid feels like a bodge to me, since having pfn_valid
> return false for something that early_pfn_valid says is valid (and is
> therefore initialised in the memmap) makes the NOMAP semantics even more
> confusing.
The concern I have had with HOLES_IN_ZONE is that it enables
pfn_valid_within() for arm64. This means that each pfn of a section is
checked which is done only once for the section otherwise. With up to
2^18 pages per section we traverse the memblock list by that factor
more often. There could be a performance regression. I haven't numbers
yet, since the fix causes another kernel crash. And, this is the next
problem I have. The crash doesn't happen otherwise. So, either it
uncovers another bug or the fix is incomplete. Though the changes look
like it should work. This needs more investigation.
-Robert
next prev parent reply other threads:[~2017-01-05 11:24 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-14 9:11 [PATCH 0/2] arm64: numa: fix spurious BUG() on NOMAP regions Ard Biesheuvel
2016-12-14 9:11 ` Ard Biesheuvel
2016-12-14 9:11 ` Ard Biesheuvel
2016-12-14 9:11 ` [PATCH 1/2] mm: don't dereference struct page fields of invalid pages Ard Biesheuvel
2016-12-14 9:11 ` Ard Biesheuvel
2016-12-14 9:11 ` Ard Biesheuvel
2017-01-04 12:16 ` Will Deacon
2017-01-04 12:16 ` Will Deacon
2017-01-04 12:16 ` Will Deacon
2016-12-14 9:11 ` [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA Ard Biesheuvel
2016-12-14 9:11 ` Ard Biesheuvel
2016-12-14 9:11 ` Ard Biesheuvel
2016-12-15 15:39 ` Robert Richter
2016-12-15 15:39 ` Robert Richter
2016-12-15 15:39 ` Robert Richter
2016-12-15 16:07 ` Ard Biesheuvel
2016-12-15 16:07 ` Ard Biesheuvel
2016-12-15 16:07 ` Ard Biesheuvel
2016-12-16 17:10 ` Robert Richter
2016-12-16 17:10 ` Robert Richter
2016-12-16 17:10 ` Robert Richter
2016-12-16 1:57 ` Hanjun Guo
2016-12-16 1:57 ` Hanjun Guo
2016-12-16 1:57 ` Hanjun Guo
2016-12-16 17:14 ` Robert Richter
2016-12-16 17:14 ` Robert Richter
2016-12-16 17:14 ` Robert Richter
2017-01-04 13:28 ` Will Deacon
2017-01-04 13:28 ` Will Deacon
2017-01-04 13:28 ` Will Deacon
2017-01-04 13:50 ` Ard Biesheuvel
2017-01-04 13:50 ` Ard Biesheuvel
2017-01-04 13:50 ` Ard Biesheuvel
2017-01-04 14:02 ` Will Deacon
2017-01-04 14:02 ` Will Deacon
2017-01-04 14:02 ` Will Deacon
2017-01-05 11:24 ` Robert Richter [this message]
2017-01-05 11:24 ` Robert Richter
2017-01-05 11:24 ` Robert Richter
2017-01-05 12:08 ` Will Deacon
2017-01-05 12:08 ` Will Deacon
2017-01-05 12:08 ` Will Deacon
2017-01-05 12:22 ` Robert Richter
2017-01-05 12:22 ` Robert Richter
2017-01-05 12:22 ` Robert Richter
2017-01-05 19:49 ` Robert Richter
2017-01-05 19:49 ` Robert Richter
2017-01-05 19:49 ` Robert Richter
2017-01-06 12:03 ` Will Deacon
2017-01-06 12:03 ` Will Deacon
2017-01-06 12:03 ` Will Deacon
2017-01-06 12:22 ` Ard Biesheuvel
2017-01-06 12:22 ` Ard Biesheuvel
2017-01-06 12:22 ` Ard Biesheuvel
2017-02-06 13:36 ` Robert Richter
2017-02-06 13:36 ` Robert Richter
2017-02-06 13:36 ` Robert Richter
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