Le 15/08/2019 à 06:10, Alastair D'Silva a écrit :
From: Alastair D'Silva <alast...@d-silva.org>
When presented with large amounts of memory being hotplugged
(in my test case, ~890GB), the call to flush_dcache_range takes
a while (~50 seconds), triggering RCU stalls.
This patch breaks up the call into 16GB chunks, calling
cond_resched() inbetween to allow the scheduler to run.
Is 16GB small enough ? If 890GB takes 50s, 16GB still takes about 1s.
I'd use 1GB chuncks to remain below 100ms.
Signed-off-by: Alastair D'Silva <alast...@d-silva.org>
---
arch/powerpc/mm/mem.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 5400da87a804..fb0d5e9aa11b 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -104,11 +104,14 @@ int __weak remove_section_mapping(unsigned long start,
unsigned long end)
return -ENODEV;
}
+#define FLUSH_CHUNK_SIZE (16ull * 1024ull * 1024ull * 1024ull)
Can we use SZ_16GB ?
+
int __ref arch_add_memory(int nid, u64 start, u64 size,
struct mhp_restrictions *restrictions)
{
unsigned long start_pfn = start >> PAGE_SHIFT;
unsigned long nr_pages = size >> PAGE_SHIFT;
+ unsigned long i;
int rc;
resize_hpt_for_hotplug(memblock_phys_mem_size());
@@ -120,7 +123,11 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
start, start + size, rc);
return -EFAULT;
}
- flush_dcache_range(start, start + size);
+
+ for (i = 0; i < size; i += FLUSH_CHUNK_SIZE) {
+ flush_dcache_range(start + i, min(start + size, start + i +
FLUSH_CHUNK_SIZE));
Isn't the line a bit long (I have not checked).
+ cond_resched();
+ }
return __add_pages(nid, start_pfn, nr_pages, restrictions);
}
@@ -131,13 +138,18 @@ void __ref arch_remove_memory(int nid, u64 start, u64
size,
unsigned long start_pfn = start >> PAGE_SHIFT;
unsigned long nr_pages = size >> PAGE_SHIFT;
struct page *page = pfn_to_page(start_pfn) + vmem_altmap_offset(altmap);
+ unsigned long i;
int ret;
__remove_pages(page_zone(page), start_pfn, nr_pages, altmap);
/* Remove htab bolted mappings for this section of memory */
start = (unsigned long)__va(start);
- flush_dcache_range(start, start + size);
+ for (i = 0; i < size; i += FLUSH_CHUNK_SIZE) {
+ flush_dcache_range(start + i, min(start + size, start + i +
FLUSH_CHUNK_SIZE));
+ cond_resched();
+ }
+
ret = remove_section_mapping(start, start + size);
WARN_ON_ONCE(ret);
Christophe
---
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