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Message-ID: <CAK1f24m9rfgWK-hXBD8nestq6BZ6eQpR6O=PZhAU3VnR54gz=A@mail.gmail.com>
Date: Mon, 28 Oct 2024 09:21:35 +0800
From: Lance Yang <ioworker0@...il.com>
To: Barry Song <21cnbao@...il.com>
Cc: Maíra Canal <mcanal@...lia.com>,
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>, 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 Maíra,
On Mon, Oct 28, 2024 at 5:54 AM Barry Song <21cnbao@...il.com> 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"?
+1
IHMO, it seems like 'thp_shmem' would be better, as it appears to fit well
with 'thp_anon' in naming style ;)
Thanks,
Lance
>
> > +
> > 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?
>
> > +__setup("thp_shmem=", setup_thp_shmem);
> > +
> > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> >
> > #else /* !CONFIG_SHMEM */
> > --
> > 2.46.2
> >
>
> Thanks
> barry
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