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Message-ID: <aa6d71d5-979d-41d7-bc5c-0ac0bc6f159a@igalia.com>
Date: Tue, 29 Oct 2024 08:13:59 -0300
From: Maíra Canal <mcanal@...lia.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>, Barry Song <baohua@...nel.org>,
David Hildenbrand <david@...hat.com>, Ryan Roberts <ryan.roberts@....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 v2 2/4] mm: shmem: control THP support through the kernel
command line
Hi Baolin,
On 28/10/24 23:03, Baolin Wang wrote:
>
>
> On 2024/10/29 08:13, Maíra Canal wrote:
>> Add a new kernel command line to control the hugepage allocation policy
>> for the internal shmem mount, ``transparent_hugepage_shmem``. The
>> parameter is similar to ``transparent_hugepage`` and has the following
>> format:
>>
>> transparent_hugepage_shmem=<policy>
>>
>> where ``<policy>`` is one of the seven valid policies available for
>> shmem.
>>
>> By configuring the default hugepage allocation policy for the internal
>> shmem mount, applications that use shmem, such as the DRM GEM objects,
>> can take advantage of mTHP before it's been configured through sysfs.
>
> Just out of curiosity, do you have any performance benefit data when
> using mTHP for DRM GEM objects?
I haven't yet benchmark mTHP with V3D (Raspberry Pi's GPU) and also I
still need to find the ideal combination of huge pages' sizes. But the
idea is to benefit from the Super Pages support that I recently
implemented in V3D [1]. Currently, I'm using a separate tmpfs mountpoint
to implement Super Pages.
I'll apply your refactor suggestion in the next version. Thanks!
[1]
https://mairacanal.github.io/unleashing-power-enabling-super-pages-on-RPi/
Best Regards,
- Maíra
>
>> Signed-off-by: Maíra Canal <mcanal@...lia.com>
>> ---
>> .../admin-guide/kernel-parameters.txt | 7 +++
>> Documentation/admin-guide/mm/transhuge.rst | 6 +++
>> mm/shmem.c | 53 +++++++++++++++----
>> 3 files changed, 57 insertions(+), 9 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/
>> Documentation/admin-guide/kernel-parameters.txt
>> index 1666576acc0e..acabb04d0dd4 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -6926,6 +6926,13 @@
>> See Documentation/admin-guide/mm/transhuge.rst
>> for more details.
>> + transparent_hugepage_shmem= [KNL]
>> + Format: [always|within_size|advise|never|deny|force]
>> + Can be used to control the hugepage allocation policy for
>> + the internal shmem mount.
>> + See Documentation/admin-guide/mm/transhuge.rst
>> + for more details.
>> +
>> trusted.source= [KEYS]
>> Format: <string>
>> This parameter identifies the trust source as a backend
>> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/
>> Documentation/admin-guide/mm/transhuge.rst
>> index 745055c3dc09..9b5b02c4d1ab 100644
>> --- a/Documentation/admin-guide/mm/transhuge.rst
>> +++ b/Documentation/admin-guide/mm/transhuge.rst
>> @@ -326,6 +326,12 @@ PMD_ORDER THP policy will be overridden. If the
>> policy for PMD_ORDER
>> is not defined within a valid ``thp_anon``, its policy will default to
>> ``never``.
>> +Similarly to ``transparent_hugepage``, you can control the hugepage
>> +allocation policy for the internal shmem mount by using the kernel
>> parameter
>> +``transparent_hugepage_shmem=<policy>``, where ``<policy>`` is one of
>> the
>> +seven valid policies for shmem (``always``, ``within_size``, ``advise``,
>> +``never``, ``deny``, and ``force``).
>> +
>> Hugepages in tmpfs/shmem
>> ========================
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 44282a296c33..26c1eb1b4b1d 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -582,7 +582,6 @@ static bool shmem_huge_global_enabled(struct inode
>> *inode, pgoff_t index,
>> }
>> }
>> -#if defined(CONFIG_SYSFS)
>> static int shmem_parse_huge(const char *str)
>> {
>> if (!strcmp(str, "never"))
>> @@ -599,7 +598,6 @@ static int shmem_parse_huge(const char *str)
>> return SHMEM_HUGE_FORCE;
>> return -EINVAL;
>> }
>> -#endif
>> #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
>> static const char *shmem_format_huge(int huge)
>> @@ -624,6 +622,20 @@ static const char *shmem_format_huge(int huge)
>> }
>> #endif
>> +static int shmem_valid_huge(int huge)
>> +{
>> + if (!has_transparent_hugepage() &&
>> + huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
>> + return -EINVAL;
>> +
>> + /* Do not override huge allocation policy with non-PMD sized mTHP */
>> + if (huge == SHMEM_HUGE_FORCE &&
>> + huge_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
>> + return -EINVAL;
>> +
>> + return 0;
>> +}
>> +
>> static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info
>> *sbinfo,
>> struct shrink_control *sc, unsigned long nr_to_free)
>> {
>> @@ -5070,14 +5082,10 @@ static ssize_t shmem_enabled_store(struct
>> kobject *kobj,
>> huge = shmem_parse_huge(tmp);
>> if (huge == -EINVAL)
>> return -EINVAL;
>> - if (!has_transparent_hugepage() &&
>> - huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
>> - return -EINVAL;
>> - /* Do not override huge allocation policy with non-PMD sized mTHP */
>> - if (huge == SHMEM_HUGE_FORCE &&
>> - huge_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
>> - return -EINVAL;
>> + err = shmem_valid_huge(huge);
>> + if (err)
>> + return err;
>> shmem_huge = huge;
>> if (shmem_huge > SHMEM_HUGE_DENY)
>> @@ -5174,6 +5182,33 @@ struct kobj_attribute thpsize_shmem_enabled_attr =
>> __ATTR(shmem_enabled, 0644, thpsize_shmem_enabled_show,
>> thpsize_shmem_enabled_store);
>> #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
>> +#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
>> +
>> +static int __init setup_transparent_hugepage_shmem(char *str)
>> +{
>> + int huge, ret = 0;
>> +
>> + if (!str)
>> + goto out;
>> +
>> + huge = shmem_parse_huge(str);
>> + if (huge == -EINVAL)
>> + goto out;
>
> Looks better. But shmem_parse_huge() is also a common part, and what I
> am thinking is below:
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index f8b8b1ad2631..646d8943950a 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -629,24 +629,39 @@ static unsigned int
> shmem_huge_global_enabled(struct inode *inode, pgoff_t index
> }
> }
>
> -#if defined(CONFIG_SYSFS)
> static int shmem_parse_huge(const char *str)
> {
> + int huge;
> +
> + if (!str)
> + return -EINVAL;
> +
> if (!strcmp(str, "never"))
> - return SHMEM_HUGE_NEVER;
> - if (!strcmp(str, "always"))
> - return SHMEM_HUGE_ALWAYS;
> - if (!strcmp(str, "within_size"))
> - return SHMEM_HUGE_WITHIN_SIZE;
> - if (!strcmp(str, "advise"))
> - return SHMEM_HUGE_ADVISE;
> - if (!strcmp(str, "deny"))
> - return SHMEM_HUGE_DENY;
> - if (!strcmp(str, "force"))
> - return SHMEM_HUGE_FORCE;
> - return -EINVAL;
> + huge = SHMEM_HUGE_NEVER;
> + else if (!strcmp(str, "always"))
> + huge = SHMEM_HUGE_ALWAYS;
> + else if (!strcmp(str, "within_size"))
> + huge = SHMEM_HUGE_WITHIN_SIZE;
> + else if (!strcmp(str, "advise"))
> + huge = SHMEM_HUGE_ADVISE;
> + else if (!strcmp(str, "deny"))
> + huge = SHMEM_HUGE_DENY;
> + else if (!strcmp(str, "force"))
> + huge = SHMEM_HUGE_FORCE;
> + else
> + return -EINVAL;
> +
> + if (!has_transparent_hugepage() &&
> + huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
> + return -EINVAL;
> +
> + /* Do not override huge allocation policy with non-PMD sized
> mTHP */
> + if (huge == SHMEM_HUGE_FORCE &&
> + huge_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
> + return -EINVAL;
> +
> + return huge;
> }
> -#endif
>
> #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
> static const char *shmem_format_huge(int huge)
> @@ -5104,16 +5119,8 @@ static ssize_t shmem_enabled_store(struct kobject
> *kobj,
> tmp[count - 1] = '\0';
>
> huge = shmem_parse_huge(tmp);
> - if (huge == -EINVAL)
> - return -EINVAL;
> - if (!has_transparent_hugepage() &&
> - huge != SHMEM_HUGE_NEVER && huge !=
> SHMEM_HUGE_DENY)
> - return -EINVAL;
> -
> - /* Do not override huge allocation policy with non-PMD sized
> mTHP */
> - if (huge == SHMEM_HUGE_FORCE &&
> - huge_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
> - return -EINVAL;
> + if (huge < 0)
> + return huge;
>
> shmem_huge = huge;
> if (shmem_huge > SHMEM_HUGE_DENY)
> @@ -5210,6 +5217,25 @@ struct kobj_attribute thpsize_shmem_enabled_attr =
> __ATTR(shmem_enabled, 0644, thpsize_shmem_enabled_show,
> thpsize_shmem_enabled_store);
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
>
> +#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
> +
> +static int __init setup_transparent_hugepage_shmem(char *str)
> +{
> + int huge;
> +
> + huge = shmem_parse_huge(str);
> + if (huge < 0) {
> + pr_warn("transparent_hugepage_shmem= cannot parse,
> ignored\n");
> + return 0;
> + }
> +
> + shmem_huge = huge;
> + return 1;
> +}
> +__setup("transparent_hugepage_shmem=", setup_transparent_hugepage_shmem);
> +
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> +
> #else /* !CONFIG_SHMEM */
>
> /*
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