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Message-ID: <d067c5d1-89b8-a71b-7b71-a8bbbd613efa@huawei.com>
Date: Tue, 24 Mar 2020 11:47:35 +0800
From: "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)"
<longpeng2@...wei.com>
To: Mina Almasry <almasrymina@...gle.com>,
Mike Kravetz <mike.kravetz@...cle.com>
CC: Linux-MM <linux-mm@...ck.org>,
open list <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linuxppc-dev@...ts.ozlabs.org>, <linux-riscv@...ts.infradead.org>,
<linux-s390@...r.kernel.org>, <sparclinux@...r.kernel.org>,
<linux-doc@...r.kernel.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
"Benjamin Herrenschmidt" <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
"Christian Borntraeger" <borntraeger@...ibm.com>,
"David S . Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"Jonathan Corbet" <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/4] hugetlbfs: clean up command line processing
On 2020/3/24 8:43, Mina Almasry wrote:
> On Wed, Mar 18, 2020 at 3:07 PM Mike Kravetz <mike.kravetz@...cle.com> wrote:
>>
>> With all hugetlb page processing done in a single file clean up code.
>
> Now that all hugepage page processing is done in a single file, clean
> up the code.
>
>> - Make code match desired semantics
>> - Update documentation with semantics
>> - Make all warnings and errors messages start with 'HugeTLB:'.
>> - Consistently name command line parsing routines.
>> - Add comments to code
>> - Describe some of the subtle interactions
>> - Describe semantics of command line arguments
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
>> ---
>> Documentation/admin-guide/mm/hugetlbpage.rst | 26 +++++++
>> mm/hugetlb.c | 78 +++++++++++++++-----
>> 2 files changed, 87 insertions(+), 17 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
>> index 1cc0bc78d10e..afc8888f33c3 100644
>> --- a/Documentation/admin-guide/mm/hugetlbpage.rst
>> +++ b/Documentation/admin-guide/mm/hugetlbpage.rst
>> @@ -100,6 +100,32 @@ with a huge page size selection parameter "hugepagesz=<size>". <size> must
>> be specified in bytes with optional scale suffix [kKmMgG]. The default huge
>> page size may be selected with the "default_hugepagesz=<size>" boot parameter.
>>
>> +Hugetlb boot command line parameter semantics
>> +hugepagesz - Specify a huge page size. Used in conjunction with hugepages
>> + parameter to preallocate a number of huge pages of the specified
>> + size. Hence, hugepagesz and hugepages are typically specified in
>> + pairs such as:
>> + hugepagesz=2M hugepages=512
>> + hugepagesz can only be specified once on the command line for a
>> + specific huge page size. Valid huge page sizes are architecture
>> + dependent.
>> +hugepages - Specify the number of huge pages to preallocate. This typically
>> + follows a valid hugepagesz parameter. However, if hugepages is the
>> + first or only hugetlb command line parameter it specifies the number
>> + of huge pages of default size to allocate. The number of huge pages
>> + of default size specified in this manner can be overwritten by a
>> + hugepagesz,hugepages parameter pair for the default size.
>> + For example, on an architecture with 2M default huge page size:
>> + hugepages=256 hugepagesz=2M hugepages=512
>> + will result in 512 2M huge pages being allocated. If a hugepages
>> + parameter is preceded by an invalid hugepagesz parameter, it will
>> + be ignored.
>> +default_hugepagesz - Specify the default huge page size. This parameter can
>> + only be specified on the command line. No other hugetlb command line
>> + parameter is associated with default_hugepagesz. Therefore, it can
>> + appear anywhere on the command line. Valid default huge page size is
>> + architecture dependent.
>
> Maybe specify what happens/should happen in a case like:
>
> hugepages=100 default_hugepagesz=1G
>
> Does that allocate 100 2MB pages or 100 1G pages? Assuming the default
> size is 2MB.
>
> Also, regarding Randy's comment. It may be nice to keep these docs in
> one place only, so we don't have to maintain 2 docs in sync.
>
>
>> +
>> When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
>> indicates the current number of pre-allocated huge pages of the default size.
>> Thus, one can use the following command to dynamically allocate/deallocate
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index cc85b4f156ca..2b9bf01db2b6 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -2954,7 +2954,7 @@ static void __init hugetlb_sysfs_init(void)
>> err = hugetlb_sysfs_add_hstate(h, hugepages_kobj,
>> hstate_kobjs, &hstate_attr_group);
>> if (err)
>> - pr_err("Hugetlb: Unable to add hstate %s", h->name);
>> + pr_err("HugeTLB: Unable to add hstate %s", h->name);
>> }
>> }
>>
>> @@ -3058,7 +3058,7 @@ static void hugetlb_register_node(struct node *node)
>> nhs->hstate_kobjs,
>> &per_node_hstate_attr_group);
>> if (err) {
>> - pr_err("Hugetlb: Unable to add hstate %s for node %d\n",
>> + pr_err("HugeTLB: Unable to add hstate %s for node %d\n",
>> h->name, node->dev.id);
>> hugetlb_unregister_node(node);
>> break;
>> @@ -3109,19 +3109,35 @@ static int __init hugetlb_init(void)
>> if (!hugepages_supported())
>> return 0;
>>
>> - if (!size_to_hstate(default_hstate_size)) {
>> - if (default_hstate_size != 0) {
>> - pr_err("HugeTLB: unsupported default_hugepagesz %lu. Reverting to %lu\n",
>> - default_hstate_size, HPAGE_SIZE);
>> - }
>> -
>> + /*
>> + * Make sure HPAGE_SIZE (HUGETLB_PAGE_ORDER) hstate exists. Some
>> + * architectures depend on setup being done here.
>> + *
>> + * If a valid default huge page size was specified on the command line,
>> + * add associated hstate if necessary. If not, set default_hstate_size
>> + * to default size. default_hstate_idx is used at runtime to identify
>> + * the default huge page size/hstate.
>> + */
>> + hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
>> + if (default_hstate_size)
>> + hugetlb_add_hstate(ilog2(default_hstate_size) - PAGE_SHIFT);
>> + else
>> default_hstate_size = HPAGE_SIZE;
>> - hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
>> - }
>> default_hstate_idx = hstate_index(size_to_hstate(default_hstate_size));
>> +
>> + /*
>> + * default_hstate_max_huge_pages != 0 indicates a count (hugepages=)
>> + * specified before a size (hugepagesz=). Use this count for the
>> + * default huge page size, unless a specific value was specified for
>> + * this size in a hugepagesz/hugepages pair.
>> + */
>> if (default_hstate_max_huge_pages) {
>> if (!default_hstate.max_huge_pages)
>> - default_hstate.max_huge_pages = default_hstate_max_huge_pages;
>> + default_hstate.max_huge_pages =
>> + default_hstate_max_huge_pages;
>> + else
>> + pr_warn("HugeTLB: First hugepages=%lu kB ignored\n",
>> + default_hstate_max_huge_pages);
>> }
>>
>> hugetlb_init_hstates();
>> @@ -3174,20 +3190,27 @@ void __init hugetlb_add_hstate(unsigned int order)
>> parsed_hstate = h;
>> }
>>
>> -static int __init hugetlb_nrpages_setup(char *s)
>> +/*
>> + * hugepages command line processing
>> + * hugepages must normally follows a valid hugepagsz specification. If not,
>
> 'hugepages must' or 'hugepages normally follows'
>> + * ignore the hugepages value. hugepages can also be the first huge page
>> + * command line option in which case it specifies the number of huge pages
>> + * for the default size.
>> + */
>> +static int __init hugepages_setup(char *s)
>> {
>> unsigned long *mhp;
>> static unsigned long *last_mhp;
>>
>> if (!parsed_valid_hugepagesz) {
>> - pr_warn("hugepages = %s preceded by "
>> + pr_warn("HugeTLB: hugepages = %s preceded by "
>> "an unsupported hugepagesz, ignoring\n", s);
>> parsed_valid_hugepagesz = true;
>> return 1;
>> }
>> /*
>> - * !hugetlb_max_hstate means we haven't parsed a hugepagesz= parameter yet,
>> - * so this hugepages= parameter goes to the "default hstate".
>> + * !hugetlb_max_hstate means we haven't parsed a hugepagesz= parameter
>> + * yet, so this hugepages= parameter goes to the "default hstate".
>> */
>> else if (!hugetlb_max_hstate)
>> mhp = &default_hstate_max_huge_pages;
>
> We don't set parsed_valid_hugepagesz to false at the end of this
> function, shouldn't we? Parsing a hugepages= value should 'consume' a
> previously defined hugepagesz= value, so that this is invalid IIUC:
>
> hugepagesz=x hugepages=z hugepages=y
>
In this case, we'll get:
"HugeTLB: hugepages= specified twice without interleaving hugepagesz=, ignoring
hugepages=y"
>> @@ -3195,7 +3218,8 @@ static int __init hugetlb_nrpages_setup(char *s)
>> mhp = &parsed_hstate->max_huge_pages;
>>
>> if (mhp == last_mhp) {
>> - pr_warn("hugepages= specified twice without interleaving hugepagesz=, ignoring\n");
>> + pr_warn("HugeTLB: hugepages= specified twice without interleaving hugepagesz=, ignoring hugepages=%s\n",
>> + s);
>> return 1;
>> }
>>
>> @@ -3214,8 +3238,15 @@ static int __init hugetlb_nrpages_setup(char *s)
>>
>> return 1;
>> }
>> -__setup("hugepages=", hugetlb_nrpages_setup);
>> +__setup("hugepages=", hugepages_setup);
>>
>> +/*
>> + * hugepagesz command line processing
>> + * A specific huge page size can only be specified once with hugepagesz.
>> + * hugepagesz is followed by hugepages on the commnad line. The global
>> + * variable 'parsed_valid_hugepagesz' is used to determine if prior
>> + * hugepagesz argument was valid.
>> + */
>> static int __init hugepagesz_setup(char *s)
>> {
>> unsigned long long size;
>> @@ -3230,16 +3261,23 @@ static int __init hugepagesz_setup(char *s)
>> }
>>
>> if (size_to_hstate(size)) {
>> + parsed_valid_hugepagesz = false;
>> pr_warn("HugeTLB: hugepagesz %s specified twice, ignoring\n",
>> saved_s);
>> return 0;
>> }
>>
>> + parsed_valid_hugepagesz = true;
>> hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
>> return 1;
>> }
>> __setup("hugepagesz=", hugepagesz_setup);
>>
>> +/*
>> + * default_hugepagesz command line input
>> + * Only one instance of default_hugepagesz allowed on command line. Do not
>> + * add hstate here as that will confuse hugepagesz/hugepages processing.
>> + */
>> static int __init default_hugepagesz_setup(char *s)
>> {
>> unsigned long long size;
>> @@ -3252,6 +3290,12 @@ static int __init default_hugepagesz_setup(char *s)
>> return 0;
>> }
>>
>> + if (default_hstate_size) {
>> + pr_err("HugeTLB: default_hugepagesz previously specified, ignoring %s\n",
>> + saved_s);
>> + return 0;
>> + }
>> +
>> default_hstate_size = size;
>> return 1;
>> }
>> --
>> 2.24.1
>>
>>
> .
>
---
Regards,
Longpeng(Mike)
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