Le 03/09/2019 à 07:23, 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 1GB chunks, calling
cond_resched() inbetween to allow the scheduler to run.
Signed-off-by: Alastair D'Silva <alast...@d-silva.org>
---
arch/powerpc/mm/mem.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index cd540123874d..854aaea2c6ae 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 SZ_1G
Maybe the name is a bit long for a local define. See if we could reduce
code line splits below by shortening this name.
+
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;
+ u64 i;
int rc;
resize_hpt_for_hotplug(memblock_phys_mem_size());
@@ -120,7 +123,12 @@ 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));
My eyes don't like it.
What about
for (; i < size; i += FLUSH_CHUNK_SIZE) {
int len = min(size - i, FLUSH_CHUNK_SIZE);
flush_dcache_range(start + i, start + i + len);
cond_resched();
}
or
end = start + size;
for (; start < end; start += FLUSH_CHUNK_SIZE, size -=
FLUSH_CHUNK_SIZE) {
int len = min(size, FLUSH_CHUNK_SIZE);
flush_dcache_range(start, start + len);
cond_resched();
}
+ cond_resched();
+ }
return __add_pages(nid, start_pfn, nr_pages, restrictions);
}
@@ -131,13 +139,19 @@ 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);
+ u64 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();
+ }
+
This piece of code looks pretty similar to the one before. Can we
refactor into a small helper ?
ret = remove_section_mapping(start, start + size);
WARN_ON_ONCE(ret);
Christophe
