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Message-ID: <2c507326-3267-431e-936a-23e2ab6a3baf@redhat.com>
Date: Thu, 31 Oct 2024 13:37:13 +0100
From: David Hildenbrand <david@...hat.com>
To: Maíra Canal <mcanal@...lia.com>,
Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>, Barry Song <baohua@...nel.org>,
Ryan Roberts <ryan.roberts@....com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>, Lance Yang <ioworker0@...il.com>
Cc: linux-mm@...ck.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel-dev@...lia.com
Subject: Re: [PATCH v3 3/4] mm: shmem: override mTHP shmem default with a
kernel parameter
On 30.10.24 13:58, Maíra Canal 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 hugepages, 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(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index acabb04d0dd4..b48d744d99b0 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.
>
> + thp_shmem= [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.
> +
> 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 dfcc88ec6e34..c2299fa0b345 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
> @@ -5027,7 +5028,8 @@ 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;
>
> @@ -5180,6 +5182,26 @@ 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;
> +}
Hm, mostly copy and paste. You could reuse existing get_order_from_str()
simply by passing in the supported orders and moving error reporting to
the caller.
static inline int get_order_from_str(const char *size_str,
int valid_orders)
{
...
if (!is_power_of_2(size))
return -EINVAL;
order = get_order(size);
if (BIT(order) & ~valid_orders)
return -EINVAL;
return order;
}
> +
> static int __init setup_transparent_hugepage_shmem(char *str)
> {
> int huge;
> @@ -5195,6 +5217,91 @@ 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;
> + strscpy(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;
> + }
> + }
> + }
Similarly, copy-paste. But not that easy to abstract :) So maybe we'll
have to keep that as is for now.
--
Cheers,
David / dhildenb
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