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Message-ID: <f2d1986a-c3bd-4a37-9028-97df44da4b11@arm.com>
Date: Fri, 19 Jul 2024 09:18:37 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Barry Song <baohua@...nel.org>
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 19/07/2024 08:52, Barry Song wrote:
> 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
OK I'll wait a couple of days to see if anyone has any feedback against this
version, then I'll re-post this on its own.
>
>>
>>>
>>>>
>>>> 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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