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Message-ID: <2505d52c-3454-4892-8c90-e3d9b2f0c84f@igalia.com>
Date: Mon, 28 Oct 2024 07:09:56 -0300
From: Maíra Canal <mcanal@...lia.com>
To: Barry Song <21cnbao@...il.com>
Cc: Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>,
David Hildenbrand <david@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>, Lance Yang
<ioworker0@...il.com>, linux-mm@...ck.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel-dev@...lia.com
Subject: Re: [PATCH 3/3] mm: shmem: override mTHP shmem default with a kernel
parameter
Hi Barry,
On 27/10/24 18:54, Barry Song wrote:
> On Mon, Oct 28, 2024 at 6:58 AM Maíra Canal <mcanal@...lia.com> wrote:
>>
>> Add the ``thp_shmem=`` kernel command line to allow specifying the
>> default policy of each supported shmem hugepage size. The kernel parameter
>> accepts the following format:
>>
>> thp_shmem=<size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
>>
>> For example,
>>
>> thp_shmem=16K-64K:always;128K,512K:inherit;256K:advise;1M-2M:never;4M-8M:within_size
>>
>> By configuring the default policy of several shmem huge pages, the user
>> can take advantage of mTHP before it's been configured through sysfs.
>>
>> Signed-off-by: Maíra Canal <mcanal@...lia.com>
>> ---
>> .../admin-guide/kernel-parameters.txt | 10 ++
>> Documentation/admin-guide/mm/transhuge.rst | 17 +++
>> mm/shmem.c | 109 +++++++++++++++++-
>> 3 files changed, 135 insertions(+), 1 deletion(-)
>>
>
> Hi Maíra,
>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index acabb04d0dd4..595fa096e28b 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -6700,6 +6700,16 @@
>> Force threading of all interrupt handlers except those
>> marked explicitly IRQF_NO_THREAD.
>>
>> + shmem_anon= [KNL]
>> + Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
>> + Control the default policy of each hugepage size for the
>> + internal shmem mount. <policy> is one of policies available
>> + for the shmem mount ("always", "inherit", "never", "within_size",
>> + and "advise").
>> + It can be used multiple times for multiple shmem THP sizes.
>> + See Documentation/admin-guide/mm/transhuge.rst for more
>> + details.
>
> I'm not sure this is the right name. How about "thp_shmem"?
Oops, sorry about that.
>
>> +
>> topology= [S390,EARLY]
>> Format: {off | on}
>> Specify if the kernel should make use of the cpu
>> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
>> index 9b5b02c4d1ab..47e7fc30e22d 100644
>> --- a/Documentation/admin-guide/mm/transhuge.rst
>> +++ b/Documentation/admin-guide/mm/transhuge.rst
>> @@ -332,6 +332,23 @@ allocation policy for the internal shmem mount by using the kernel parameter
>> seven valid policies for shmem (``always``, ``within_size``, ``advise``,
>> ``never``, ``deny``, and ``force``).
>>
>> +In the same manner as ``thp_anon`` controls each supported anonymous THP
>> +size, ``thp_shmem`` controls each supported shmem THP size. ``thp_shmem``
>> +has the same format as ``thp_anon``, but also supports the policy
>> +``within_size``.
>> +
>> +``thp_shmem=`` may be specified multiple times to configure all THP sizes
>> +as required. If ``thp_shmem=`` is specified at least once, any shmem THP
>> +sizes not explicitly configured on the command line are implicitly set to
>> +``never``.
>> +
>> +``transparent_hugepage_shmem`` setting only affects the global toggle. If
>> +``thp_shmem`` is not specified, PMD_ORDER hugepage will default to
>> +``inherit``. However, if a valid ``thp_shmem`` setting is provided by the
>> +user, the PMD_ORDER hugepage policy will be overridden. If the policy for
>> +PMD_ORDER is not defined within a valid ``thp_shmem``, its policy will
>> +default to ``never``.
>> +
>> Hugepages in tmpfs/shmem
>> ========================
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 24cdeafd8260..0a7a7d04f725 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -136,6 +136,7 @@ static unsigned long huge_shmem_orders_always __read_mostly;
>> static unsigned long huge_shmem_orders_madvise __read_mostly;
>> static unsigned long huge_shmem_orders_inherit __read_mostly;
>> static unsigned long huge_shmem_orders_within_size __read_mostly;
>> +static bool shmem_orders_configured __initdata;
>> #endif
>>
>> #ifdef CONFIG_TMPFS
>> @@ -5013,7 +5014,8 @@ void __init shmem_init(void)
>> * Default to setting PMD-sized THP to inherit the global setting and
>> * disable all other multi-size THPs.
>> */
>> - huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER);
>> + if (!shmem_orders_configured)
>> + huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER);
>> #endif
>> return;
>>
>> @@ -5174,6 +5176,26 @@ struct kobj_attribute thpsize_shmem_enabled_attr =
>>
>> #if defined(CONFIG_TRANSPARENT_HUGEPAGE)
>>
>> +static inline int get_order_from_str(const char *size_str)
>> +{
>> + unsigned long size;
>> + char *endptr;
>> + int order;
>> +
>> + size = memparse(size_str, &endptr);
>> +
>> + if (!is_power_of_2(size))
>> + goto err;
>> + order = get_order(size);
>> + if (BIT(order) & ~THP_ORDERS_ALL_FILE_DEFAULT)
>> + goto err;
>> +
>> + return order;
>> +err:
>> + pr_err("invalid size %s in thp_shmem boot parameter\n", size_str);
>> + return -EINVAL;
>> +}
>> +
>> static int __init setup_transparent_hugepage_shmem(char *str)
>> {
>> int huge, ret = 0;
>> @@ -5206,6 +5228,91 @@ static int __init setup_transparent_hugepage_shmem(char *str)
>> }
>> __setup("transparent_hugepage_shmem=", setup_transparent_hugepage_shmem);
>>
>> +static char str_dup[PAGE_SIZE] __initdata;
>> +static int __init setup_thp_shmem(char *str)
>> +{
>> + char *token, *range, *policy, *subtoken;
>> + unsigned long always, inherit, madvise, within_size;
>> + char *start_size, *end_size;
>> + int start, end, nr;
>> + char *p;
>> +
>> + if (!str || strlen(str) + 1 > PAGE_SIZE)
>> + goto err;
>> + strcpy(str_dup, str);
>> +
>> + always = huge_shmem_orders_always;
>> + inherit = huge_shmem_orders_inherit;
>> + madvise = huge_shmem_orders_madvise;
>> + within_size = huge_shmem_orders_within_size;
>> + p = str_dup;
>> + while ((token = strsep(&p, ";")) != NULL) {
>> + range = strsep(&token, ":");
>> + policy = token;
>> +
>> + if (!policy)
>> + goto err;
>> +
>> + while ((subtoken = strsep(&range, ",")) != NULL) {
>> + if (strchr(subtoken, '-')) {
>> + start_size = strsep(&subtoken, "-");
>> + end_size = subtoken;
>> +
>> + start = get_order_from_str(start_size);
>> + end = get_order_from_str(end_size);
>> + } else {
>> + start = end = get_order_from_str(subtoken);
>> + }
>> +
>> + if (start < 0 || end < 0 || start > end)
>> + goto err;
>> +
>> + nr = end - start + 1;
>> + if (!strcmp(policy, "always")) {
>> + bitmap_set(&always, start, nr);
>> + bitmap_clear(&inherit, start, nr);
>> + bitmap_clear(&madvise, start, nr);
>> + bitmap_clear(&within_size, start, nr);
>> + } else if (!strcmp(policy, "advise")) {
>> + bitmap_set(&madvise, start, nr);
>> + bitmap_clear(&inherit, start, nr);
>> + bitmap_clear(&always, start, nr);
>> + bitmap_clear(&within_size, start, nr);
>> + } else if (!strcmp(policy, "inherit")) {
>> + bitmap_set(&inherit, start, nr);
>> + bitmap_clear(&madvise, start, nr);
>> + bitmap_clear(&always, start, nr);
>> + bitmap_clear(&within_size, start, nr);
>> + } else if (!strcmp(policy, "within_size")) {
>> + bitmap_set(&within_size, start, nr);
>> + bitmap_clear(&inherit, start, nr);
>> + bitmap_clear(&madvise, start, nr);
>> + bitmap_clear(&always, start, nr);
>> + } else if (!strcmp(policy, "never")) {
>> + bitmap_clear(&inherit, start, nr);
>> + bitmap_clear(&madvise, start, nr);
>> + bitmap_clear(&always, start, nr);
>> + bitmap_clear(&within_size, start, nr);
>> + } else {
>> + pr_err("invalid policy %s in thp_shmem boot parameter\n", policy);
>> + goto err;
>> + }
>> + }
>> + }
>> +
>> + huge_shmem_orders_always = always;
>> + huge_shmem_orders_madvise = madvise;
>> + huge_shmem_orders_inherit = inherit;
>> + huge_shmem_orders_within_size = within_size;
>> + shmem_orders_configured = true;
>> + return 1;
>> +
>> +err:
>> + pr_warn("thp_shmem=%s: error parsing string, ignoring setting\n", str);
>> + return 0;
>> +}
>
> Can we share source code with thp_anon since there's a lot of duplication?
I'm not a regular mm contributor and I'm most usually around drivers, so
I don't know exactly here I could add shared code. Should I add the
headers to "internal.h"?
Best Regards,
- Maíra
>
>> +__setup("thp_shmem=", setup_thp_shmem);
>> +
>> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>>
>> #else /* !CONFIG_SHMEM */
>> --
>> 2.46.2
>>
>
> Thanks
> barry
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