Re: [Crash-utility] [PATCH] Fix for "ps/vm" commands to display correct %MEM and RSS values
On 2022/11/09 15:21, Lianbo Jiang wrote:
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(a)redhat.com>
The patch looks good, applied.
https://github.com/crash-utility/crash/commit/a158590f475c8d6d504b0c5e28b...
Thanks,
Kazu
> ---
> 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;