Re: [PATCH v3] mm/mm_init: use node's number of cpus in deferred_page_init_max_threads
From: Mike Rapoport <rppt@kernel.org>
Date: 2024-05-29 05:32:19
Also in:
linux-arm-kernel, linux-mm, linux-s390, lkml
On Tue, May 28, 2024 at 02:54:58PM -0400, Eric Chanudet wrote:
When DEFERRED_STRUCT_PAGE_INIT=y, use a node's cpu count as maximum
thread count for the deferred initialization of struct pages via padata.
This should result in shorter boot times for these configurations by
going through page_alloc_init_late() faster as systems tend not to be
under heavy load that early in the bootstrap.
Only x86_64 does that now. Make it archs agnostic when
DEFERRED_STRUCT_PAGE_INIT is set. With the default defconfigs, that
includes powerpc and s390.
It used to be so before offering archs to override the function for
tuning with commit ecd096506922 ("mm: make deferred init's max threads
arch-specific").
Setting DEFERRED_STRUCT_PAGE_INIT and testing on a few arm64 platforms
shows faster deferred_init_memmap completions:
| | x13s | SA8775p-ride | Ampere R137-P31 | Ampere HR330 |
| | Metal, 32GB | VM, 36GB | VM, 58GB | Metal, 128GB |
| | 8cpus | 8cpus | 8cpus | 32cpus |
|---------|-------------|--------------|-----------------|--------------|
| threads | ms (%) | ms (%) | ms (%) | ms (%) |
|---------|-------------|--------------|-----------------|--------------|
| 1 | 108 (0%) | 72 (0%) | 224 (0%) | 324 (0%) |
| cpus | 24 (-77%) | 36 (-50%) | 40 (-82%) | 56 (-82%) |
Michael Ellerman on a powerpc machine (1TB, 40 cores, 4KB pages) reports
faster deferred_init_memmap from 210-240ms to 90-110ms between nodes.
Signed-off-by: Eric Chanudet <redacted>
Tested-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
quoted hunk ↗ jump to hunk
--- - v1: https://lore.kernel.org/linux-arm-kernel/20240520231555.395979-5-echanude@redhat.com (local) - Changes since v1: - Make the generic function return the number of cpus of the node as max threads limit instead overriding it for arm64. - Drop Baoquan He's R-b on v1 since the logic changed. - Add CCs according to patch changes (ppc and s390 set DEFERRED_STRUCT_PAGE_INIT by default). - v2: https://lore.kernel.org/linux-arm-kernel/20240522203758.626932-4-echanude@redhat.com/ (local) - Changes since v2: - deferred_page_init_max_threads returns unsigned and use max instead of max_t. - Make deferred_page_init_max_threads static since there are no more override. - Rephrase description. - Add T-b and report from Michael Ellerman. arch/x86/mm/init_64.c | 12 ------------ include/linux/memblock.h | 2 -- mm/mm_init.c | 5 ++--- 3 files changed, 2 insertions(+), 17 deletions(-)diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 7e177856ee4f..adec42928ec1 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c@@ -1354,18 +1354,6 @@ void __init mem_init(void) preallocate_vmalloc_pages(); } -#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT -int __init deferred_page_init_max_threads(const struct cpumask *node_cpumask) -{ - /* - * More CPUs always led to greater speedups on tested systems, up to - * all the nodes' CPUs. Use all since the system is otherwise idle - * now. - */ - return max_t(int, cpumask_weight(node_cpumask), 1); -} -#endif - int kernel_set_to_readonly; void mark_rodata_ro(void)diff --git a/include/linux/memblock.h b/include/linux/memblock.h index e2082240586d..40c62aca36ec 100644 --- a/include/linux/memblock.h +++ b/include/linux/memblock.h@@ -335,8 +335,6 @@ void __next_mem_pfn_range_in_zone(u64 *idx, struct zone *zone, for (; i != U64_MAX; \ __next_mem_pfn_range_in_zone(&i, zone, p_start, p_end)) -int __init deferred_page_init_max_threads(const struct cpumask *node_cpumask); - #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */ /**diff --git a/mm/mm_init.c b/mm/mm_init.c index f72b852bd5b8..acfeba508796 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c@@ -2122,11 +2122,10 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn, } } -/* An arch may override for more concurrency. */ -__weak int __init +static unsigned int __init deferred_page_init_max_threads(const struct cpumask *node_cpumask) { - return 1; + return max(cpumask_weight(node_cpumask), 1U); } /* Initialise remaining memory on a node */-- 2.44.0
-- Sincerely yours, Mike.