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Message-ID: <CAGsJ_4xSDc8pX+-vOUcXtV_ivt0Jc-LECiC=tto9oxYeOtU38Q@mail.gmail.com>
Date: Fri, 19 Jul 2024 19:52:32 +1200
From: Barry Song <baohua@...nel.org>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>,
Jonathan Corbet <corbet@....net>, "Matthew Wilcox (Oracle)" <willy@...radead.org>,
David Hildenbrand <david@...hat.com>, Lance Yang <ioworker0@...il.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>, Gavin Shan <gshan@...hat.com>,
Pankaj Raghav <kernel@...kajraghav.com>, Daniel Gomez <da.gomez@...sung.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH v1 3/4] mm: Override mTHP "enabled" defaults at kernel cmdline
On Fri, Jul 19, 2024 at 7:48 PM Ryan Roberts <ryan.roberts@....com> wrote:
>
> On 19/07/2024 01:46, Barry Song wrote:
> > On Wed, Jul 17, 2024 at 7:13 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.
> >
> > This is exactly what I need and want to implement, as the current behavior
> > is problematic. We need to boot up the system and reach the point where
> > we can set up the sys interfaces to enable mTHP. Many processes miss the
> > opportunity to use mTHP.
> >
> > On the other hand, userspace might have been tuned to detect that mTHP
> > is enabled, such as a .so library. However, it turns out we have had
> > inconsistent settings between the two stages - before and after setting
> > mTHP enabled by sys interfaces.
>
> Good feedback - sounds like I should separate out this patch from the rest of
> the series to get it reviewed and merged faster?
+1
>
> >
> >>
> >> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> >> ---
> >> .../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 bc55fb55cd26..48443ad12e3f 100644
> >> --- a/Documentation/admin-guide/kernel-parameters.txt
> >> +++ b/Documentation/admin-guide/kernel-parameters.txt
> >> @@ -6592,6 +6592,14 @@
> >> <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 1aaf8e3a0b5a..f53d43d986e2 100644
> >> --- a/Documentation/admin-guide/mm/transhuge.rst
> >> +++ b/Documentation/admin-guide/mm/transhuge.rst
> >> @@ -311,13 +311,27 @@ performance.
> >> Note that any changes to the allowed set of sizes only applies to future
> >> file-backed THP allocations.
> >>
> >> -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 4249c0bc9388..794d2790d90d 100644
> >> --- a/mm/huge_memory.c
> >> +++ b/mm/huge_memory.c
> >> @@ -82,6 +82,7 @@ unsigned long huge_anon_orders_madvise __read_mostly;
> >> unsigned long huge_anon_orders_inherit __read_mostly;
> >> unsigned long huge_file_orders_always __read_mostly;
> >> int huge_file_exec_order __read_mostly = -1;
> >> +static bool anon_orders_configured;
> >>
> >> unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
> >> unsigned long vm_flags,
> >> @@ -763,7 +764,10 @@ 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;
> >> + }
> >>
> >> /*
> >> * For pagecache, default to enabling all orders. powerpc's PMD_ORDER
> >> @@ -955,6 +959,55 @@ 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;
> >> +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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