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Subject[PATCH v3 16/21] x86/clear_page: add arch_clear_page_non_caching_threshold()
Date
Add arch_clear_page_non_caching_threshold() for a machine specific value
above which clear_page_incoherent() would be used.

The ideal threshold value depends on the CPU model and where the
performance curves for caching and non-caching stores intersect.
A safe value is LLC-size, so we use that of the boot_cpu.

Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
arch/x86/include/asm/cacheinfo.h | 1 +
arch/x86/kernel/cpu/cacheinfo.c | 13 +++++++++++++
arch/x86/kernel/setup.c | 6 ++++++
3 files changed, 20 insertions(+)

diff --git a/arch/x86/include/asm/cacheinfo.h b/arch/x86/include/asm/cacheinfo.h
index 86b2e0dcc4bf..5c6045699e94 100644
--- a/arch/x86/include/asm/cacheinfo.h
+++ b/arch/x86/include/asm/cacheinfo.h
@@ -4,5 +4,6 @@

void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, int cpu);
void cacheinfo_hygon_init_llc_id(struct cpuinfo_x86 *c, int cpu);
+int cacheinfo_lookup_max_size(int cpu);

#endif /* _ASM_X86_CACHEINFO_H */
diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index fe98a1465be6..6fb0cb868099 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -1034,3 +1034,16 @@ int populate_cache_leaves(unsigned int cpu)

return 0;
}
+
+int cacheinfo_lookup_max_size(int cpu)
+{
+ struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
+ struct cacheinfo *this_leaf = this_cpu_ci->info_list;
+ struct cacheinfo *max_leaf;
+
+ /*
+ * Assume that cache sizes always increase with level.
+ */
+ max_leaf = this_leaf + this_cpu_ci->num_leaves - 1;
+ return max_leaf->size;
+}
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 249981bf3d8a..701825a22863 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -50,6 +50,7 @@
#include <asm/thermal.h>
#include <asm/unwind.h>
#include <asm/vsyscall.h>
+#include <asm/cacheinfo.h>
#include <linux/vmalloc.h>

/*
@@ -1293,3 +1294,8 @@ static int __init register_kernel_offset_dumper(void)
return 0;
}
__initcall(register_kernel_offset_dumper);
+
+unsigned long __init arch_clear_page_non_caching_threshold(void)
+{
+ return cacheinfo_lookup_max_size(0);
+}
--
2.31.1
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