The ps/vm commands may print the bogus value of the %MEM and RSS, the
reason is that the counter of rss stat is updated in asynchronous manner
and may become negative, when the SPLIT_RSS_COUNTING is enabled in kernel.
As a result, crash will read it from memory and convert from negative to
unsigned long integer, eventually it overflows and gets a big integer. For
example:
crash> ps 1393
PID PPID CPU TASK ST %MEM VSZ RSS COMM
1393 1 24 ffff9584bb542100 RU 541298032135.9 4132 18014398509481908 enlinuxpc64
^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^
This is unexpected, crash needs to correct its value for this case.
Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
---
memory.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/memory.c b/memory.c
index 8724c4aa3d8a..9c15c1b745ef 100644
--- a/memory.c
+++ b/memory.c
@@ -4714,18 +4714,29 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
* Latest kernels have mm_struct.mm_rss_stat[].
*/
if (VALID_MEMBER(mm_struct_rss_stat)) {
- long anonpages, filepages;
+ long anonpages, filepages, count;
anonpages = tt->anonpages;
filepages = tt->filepages;
- rss += LONG(tt->mm_struct +
+ count = LONG(tt->mm_struct +
OFFSET(mm_struct_rss_stat) +
OFFSET(mm_rss_stat_count) +
(filepages * sizeof(long)));
- rss += LONG(tt->mm_struct +
+
+ /*
+ * The counter is updated in asynchronous manner
+ * and may become negative, see:
+ * include/linux/mm.h: get_mm_counter()
+ */
+ if (count > 0)
+ rss += count;
+
+ count = LONG(tt->mm_struct +
OFFSET(mm_struct_rss_stat) +
OFFSET(mm_rss_stat_count) +
(anonpages * sizeof(long)));
+ if (count > 0)
+ rss += count;
}
/* Check whether SPLIT_RSS_COUNTING is enabled */
@@ -4769,7 +4780,8 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
RETURN_ON_ERROR))
continue;
- rss_cache += sync_rss;
+ if (sync_rss > 0)
+ rss_cache += sync_rss;
/* count 1 -> anonpages */
if (!readmem(first->task +
@@ -4782,7 +4794,8 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
RETURN_ON_ERROR))
continue;
- rss_cache += sync_rss;
+ if (sync_rss > 0)
+ rss_cache += sync_rss;
if (first == last)
break;
--
2.37.1
--
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