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Message-ID: <CAGsJ_4x8ruPspuk_FQVggJMWcXLbRuZFq44gg-Dt7Ewt3ExqTw@mail.gmail.com>
Date: Fri, 9 Aug 2024 16:31:10 +0800
From: Barry Song <baohua@...nel.org>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Jonathan Corbet <corbet@....net>,
David Hildenbrand <david@...hat.com>, Lance Yang <ioworker0@...il.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: Override mTHP "enabled" defaults at kernel cmdline
On Fri, Aug 9, 2024 at 3:58 PM Ryan Roberts <ryan.roberts@....com> wrote:
>
> On 08/08/2024 22:17, Barry Song wrote:
> > On Thu, Aug 8, 2024 at 10:17 PM Ryan Roberts <ryan.roberts@....com> wrote:
> >>
> >> Add thp_anon= cmdline parameter to allow specifying the default
> >> enablement of each supported anon THP size. The parameter accepts the
> >> following format and can be provided multiple times to configure each
> >> size:
> >>
> >> thp_anon=<size>[KMG]:<value>
> >>
> >> See Documentation/admin-guide/mm/transhuge.rst for more details.
> >>
> >> Configuring the defaults at boot time is useful to allow early user
> >> space to take advantage of mTHP before its been configured through
> >> sysfs.
> >>
> >> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> >> ---
> >>
> >> Hi All,
> >>
> >> I've split this off from my RFC at [1] because Barry highlighted that he would
> >> benefit from it immediately [2]. There are no changes vs the version in that
> >> series.
> >>
> >> It applies against today's mm-unstable (275d686abcb59). (although I had to fix a
> >> minor build bug in stackdepot.c due to MIN() not being defined in this tree).
> >>
> >> Thanks,
> >> Ryan
> >>
> >>
> >> .../admin-guide/kernel-parameters.txt | 8 +++
> >> Documentation/admin-guide/mm/transhuge.rst | 26 +++++++--
> >> mm/huge_memory.c | 55 ++++++++++++++++++-
> >> 3 files changed, 82 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> >> index bcdee8984e1f0..5c79b58c108ec 100644
> >> --- a/Documentation/admin-guide/kernel-parameters.txt
> >> +++ b/Documentation/admin-guide/kernel-parameters.txt
> >> @@ -6631,6 +6631,14 @@
> >> <deci-seconds>: poll all this frequency
> >> 0: no polling (default)
> >>
> >> + thp_anon= [KNL]
> >> + Format: <size>[KMG]:always|madvise|never|inherit
> >> + Can be used to control the default behavior of the
> >> + system with respect to anonymous transparent hugepages.
> >> + Can be used multiple times for multiple anon THP sizes.
> >> + See Documentation/admin-guide/mm/transhuge.rst for more
> >> + details.
> >> +
> >> threadirqs [KNL,EARLY]
> >> Force threading of all interrupt handlers except those
> >> marked explicitly IRQF_NO_THREAD.
> >> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> >> index 24eec1c03ad88..f63b0717366c6 100644
> >> --- a/Documentation/admin-guide/mm/transhuge.rst
> >> +++ b/Documentation/admin-guide/mm/transhuge.rst
> >> @@ -284,13 +284,27 @@ that THP is shared. Exceeding the number would block the collapse::
> >>
> >> A higher value may increase memory footprint for some workloads.
> >>
> >> -Boot parameter
> >> -==============
> >> +Boot parameters
> >> +===============
> >>
> >> -You can change the sysfs boot time defaults of Transparent Hugepage
> >> -Support by passing the parameter ``transparent_hugepage=always`` or
> >> -``transparent_hugepage=madvise`` or ``transparent_hugepage=never``
> >> -to the kernel command line.
> >> +You can change the sysfs boot time default for the top-level "enabled"
> >> +control by passing the parameter ``transparent_hugepage=always`` or
> >> +``transparent_hugepage=madvise`` or ``transparent_hugepage=never`` to the
> >> +kernel command line.
> >> +
> >> +Alternatively, each supported anonymous THP size can be controlled by
> >> +passing ``thp_anon=<size>[KMG]:<state>``, where ``<size>`` is the THP size
> >> +and ``<state>`` is one of ``always``, ``madvise``, ``never`` or
> >> +``inherit``.
> >> +
> >> +For example, the following will set 64K THP to ``always``::
> >> +
> >> + thp_anon=64K:always
> >> +
> >> +``thp_anon=`` may be specified multiple times to configure all THP sizes as
> >> +required. If ``thp_anon=`` is specified at least once, any anon THP sizes
> >> +not explicitly configured on the command line are implicitly set to
> >> +``never``.
> >>
> >> Hugepages in tmpfs/shmem
> >> ========================
> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >> index 0c3075ee00012..c2c0da1eb94e6 100644
> >> --- a/mm/huge_memory.c
> >> +++ b/mm/huge_memory.c
> >> @@ -82,6 +82,7 @@ unsigned long huge_zero_pfn __read_mostly = ~0UL;
> >> unsigned long huge_anon_orders_always __read_mostly;
> >> unsigned long huge_anon_orders_madvise __read_mostly;
> >> unsigned long huge_anon_orders_inherit __read_mostly;
> >> +static bool anon_orders_configured;
> >>
> >> unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
> >> unsigned long vm_flags,
> >> @@ -672,7 +673,10 @@ static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
> >> * disable all other sizes. powerpc's PMD_ORDER isn't a compile-time
> >> * constant so we have to do this here.
> >> */
> >> - huge_anon_orders_inherit = BIT(PMD_ORDER);
> >> + if (!anon_orders_configured) {
> >> + huge_anon_orders_inherit = BIT(PMD_ORDER);
> >> + anon_orders_configured = true;
> >> + }
> >
> > If a user configures 64KB and doesn't adjust anything for PMD_ORDER,
> > then PMD_ORDER will be set to "never", correct? This seems to change
> > the default behavior of PMD_ORDER. Could we instead achieve this by
> > checking if PMD_ORDER has been explicitly configured?
>
> Yes, that's how it's implemented in this patch, and the accompanying docs also
> state:
>
> If ``thp_anon=`` is specified at least once, any anon THP sizes
> not explicitly configured on the command line are implicitly set to
> ``never``.
>
> My initial approach did exactly as you suggest. But in the original series, I
> also had a similar patch to configure file thp with "thp_file=". And for file,
> all of the orders default to `always`. So if taking the same approach with that
> control, the user would have to explicitly opt-out of all supported orders
> rather than just opt-in to the orders they want. And I thought that could get
> tricky in future if support is added for more orders. I felt that was
> potentially very confusing so decided it was clearer to have the above rule and
> make both controls consistent.
>
> What do you think?
If this is the intention, once the user sets the command line, they should
realize that the default settings have been overridden. I am perfectly fine
with this strategy.
with the below cmdline:
thp_anon=64K:always thp_anon=8K:inherit thp_anon=32K:madvise
thp_anon=1M:inherit thp_anon=2M:always
I am getting:
/ # cat /sys/kernel/mm/transparent_hugepage/hugepages-64kB/enabled
[always] inherit madvise never
/ # cat /sys/kernel/mm/transparent_hugepage/hugepages-32kB/enabled
always inherit [madvise] never
/ # cat /sys/kernel/mm/transparent_hugepage/hugepages-1024kB/enabled
always [inherit] madvise never
/ # cat /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled
[always] inherit madvise never
Thus,
Tested-by: Barry Song <baohua@...nel.org>
>
>
> >
> >>
> >> *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
> >> if (unlikely(!*hugepage_kobj)) {
> >> @@ -857,6 +861,55 @@ static int __init setup_transparent_hugepage(char *str)
> >> }
> >> __setup("transparent_hugepage=", setup_transparent_hugepage);
> >>
> >> +static int __init setup_thp_anon(char *str)
> >> +{
> >> + unsigned long size;
> >> + char *state;
> >> + int order;
> >> + int ret = 0;
> >> +
> >> + if (!str)
> >> + goto out;
> >> +
> >> + size = (unsigned long)memparse(str, &state);
> >> + order = ilog2(size >> PAGE_SHIFT);
> >> + if (*state != ':' || !is_power_of_2(size) || size <= PAGE_SIZE ||
> >> + !(BIT(order) & THP_ORDERS_ALL_ANON))
> >> + goto out;
> >> +
> >> + state++;
> >> +
> >> + if (!strcmp(state, "always")) {
> >> + clear_bit(order, &huge_anon_orders_inherit);
> >> + clear_bit(order, &huge_anon_orders_madvise);
> >> + set_bit(order, &huge_anon_orders_always);
> >> + ret = 1;
> >> + } else if (!strcmp(state, "inherit")) {
> >> + clear_bit(order, &huge_anon_orders_always);
> >> + clear_bit(order, &huge_anon_orders_madvise);
> >> + set_bit(order, &huge_anon_orders_inherit);
> >> + ret = 1;
> >> + } else if (!strcmp(state, "madvise")) {
> >> + clear_bit(order, &huge_anon_orders_always);
> >> + clear_bit(order, &huge_anon_orders_inherit);
> >> + set_bit(order, &huge_anon_orders_madvise);
> >> + ret = 1;
> >> + } else if (!strcmp(state, "never")) {
> >> + clear_bit(order, &huge_anon_orders_always);
> >> + clear_bit(order, &huge_anon_orders_inherit);
> >> + clear_bit(order, &huge_anon_orders_madvise);
> >> + ret = 1;
> >> + }
> >> +
> >> + if (ret)
> >> + anon_orders_configured = true;
> >
> > I mean:
> >
> > if (ret && order == PMD_ORDER)
> > anon_pmd_order_configured = true;
> >
> >> +out:
> >> + if (!ret)
> >> + pr_warn("thp_anon=%s: cannot parse, ignored\n", str);
> >> + return ret;
> >> +}
> >> +__setup("thp_anon=", setup_thp_anon);
> >> +
> >> pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
> >> {
> >> if (likely(vma->vm_flags & VM_WRITE))
> >> --
> >> 2.43.0
> >>
> >
> > Thanks
> > Barry
>
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