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Message-ID: <899284fa-953f-48a1-af29-222d0d55881c@igalia.com>
Date: Thu, 31 Oct 2024 09:51:05 -0300
From: Maíra Canal <mcanal@...lia.com>
To: David Hildenbrand <david@...hat.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
Hi David,
On 31/10/24 09:37, David Hildenbrand wrote:
> 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/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.
>
Can I use functions from mm/huge_memory.c here?
> 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.
On v2 [1], I abstracted to reduce copy and paste, but me and Barry
agreed that adding this sort of header to linux/huge_mm.h was weird.
[1]
https://lore.kernel.org/linux-mm/20241029002324.1062723-4-mcanal@igalia.com/
Best Regards,
- Maíra
>
>
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