Around 95% of memory is reserved by fadump/capture kernel. All this
memory is freed, one page at a time, on writing '1' to the node
/sys/kernel/fadump_release_mem. On systems with large memory, this
can take a long time to complete, leading to soft lockup warning
messages. To avoid this, add reschedule points at regular intervals.
Suggested-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Hari Bathini <hbath...@linux.vnet.ibm.com>
---
arch/powerpc/kernel/fadump.c | 60 ++++++++++++++++++++++++++++++++++--------
1 file changed, 49 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 466569e..0babefc 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -1046,28 +1046,66 @@ void fadump_cleanup(void)
}
}
+/* Time to wait before a reschedule point */
+#define RELEASE_TIME_LIMIT 500 /* in milliseconds */
+
+/* Release memory in batches of 'N' pages each */
+#define RELEASE_PAGES_BATCH (1 << 22)
+
+static void fadump_free_reserved_memory(unsigned long start, unsigned long end)
+{
+ unsigned long pfn, start_pfn, end_pfn;
+ unsigned int remaining = end > start ? (end - start) >> PAGE_SHIFT : 0;
+ unsigned long time_limit = jiffies +
+ msecs_to_jiffies(RELEASE_TIME_LIMIT);
+
+ while (remaining) {
+ /* A reschedule point for every 'X' milliseconds */
+ if (time_after_eq(jiffies, time_limit)) {
+ cond_resched();
+ time_limit = jiffies +
+ msecs_to_jiffies(RELEASE_TIME_LIMIT);
+ }
+
+ /* release memory in batches of 'N' pages */
+ start_pfn = start >> PAGE_SHIFT;
+ if (remaining > RELEASE_PAGES_BATCH) {
+ end_pfn = start_pfn + RELEASE_PAGES_BATCH;
+ remaining -= RELEASE_PAGES_BATCH;
+ } else {
+ end_pfn = end >> PAGE_SHIFT;
+ remaining = 0;
+ }
+
+ for (pfn = start_pfn; pfn < end_pfn; pfn++)
+ free_reserved_page(pfn_to_page(pfn));
+
+ start = end_pfn << PAGE_SHIFT;
+ }
+}
+
/*
* Release the memory that was reserved in early boot to preserve the memory
* contents. The released memory will be available for general use.
*/
static void fadump_release_memory(unsigned long begin, unsigned long end)
{
- unsigned long addr;
unsigned long ra_start, ra_end;
ra_start = fw_dump.reserve_dump_area_start;
ra_end = ra_start + fw_dump.reserve_dump_area_size;
- for (addr = begin; addr < end; addr += PAGE_SIZE) {
- /*
- * exclude the dump reserve area. Will reuse it for next
- * fadump registration.
- */
- if (addr <= ra_end && ((addr + PAGE_SIZE) > ra_start))
- continue;
-
- free_reserved_page(pfn_to_page(addr >> PAGE_SHIFT));
- }
+ /*
+ * exclude the dump reserve area. Will reuse it for next
+ * fadump registration.
+ */
+ if (begin < ra_end && end > ra_start) {
+ if (begin < ra_start)
+ fadump_free_reserved_memory(begin, ra_start);
+ if (end > ra_end)
+ fadump_free_reserved_memory(ra_end, end);
+ } else
+ fadump_free_reserved_memory(begin, end);
}
static void fadump_invalidate_release_mem(void)
