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Message-ID: <CAGsJ_4y13T+KE1hJPb=14LBvGixd4uQTcN5pS=Hok6Ca6RD+7g@mail.gmail.com>
Date: Mon, 28 Oct 2024 19:09:37 +0800
From: Barry Song <21cnbao@...il.com>
To: Maíra Canal <mcanal@...lia.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
On Mon, Oct 28, 2024 at 6:10 PM Maíra Canal <mcanal@...lia.com> wrote:
>
> 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"?
My comment isn't related to drivers or memory management. It's solely about
avoiding code duplication. For example, we could create a shared function to
handle both controls, reducing redundant code :-)
>
> 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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