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From 74fe453f2b5ddf1e1571d006d486cb214817a0ed Mon Sep 17 00:00:00 2001
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From: Lianbo Jiang <lijiang@redhat.com>
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Date: Wed, 9 Nov 2022 14:21:57 +0800
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Subject: [PATCH 28/28] Fix for "ps/vm" commands to display correct %MEM and
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RSS values
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The ps/vm commands may print the bogus value of the %MEM and RSS, the
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reason is that the counter of rss stat is updated in asynchronous manner
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and may become negative, when the SPLIT_RSS_COUNTING is enabled in kernel.
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As a result, crash will read it from memory and convert from negative to
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unsigned long integer, eventually it overflows and gets a big integer. For
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example:
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crash> ps 1393
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PID PPID CPU TASK ST %MEM VSZ RSS COMM
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1393 1 24 ffff9584bb542100 RU 541298032135.9 4132 18014398509481908 enlinuxpc64
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^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^
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This is unexpected, crash needs to correct its value for this case.
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Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
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---
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memory.c | 23 ++++++++++++++++++-----
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1 file changed, 18 insertions(+), 5 deletions(-)
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diff --git a/memory.c b/memory.c
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index ddbf458277f0..2167281b6039 100644
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--- a/memory.c
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+++ b/memory.c
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@@ -4714,18 +4714,29 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
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* Latest kernels have mm_struct.mm_rss_stat[].
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*/
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if (VALID_MEMBER(mm_struct_rss_stat)) {
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- long anonpages, filepages;
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+ long anonpages, filepages, count;
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anonpages = tt->anonpages;
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filepages = tt->filepages;
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- rss += LONG(tt->mm_struct +
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+ count = LONG(tt->mm_struct +
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OFFSET(mm_struct_rss_stat) +
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OFFSET(mm_rss_stat_count) +
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(filepages * sizeof(long)));
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- rss += LONG(tt->mm_struct +
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+
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+ /*
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+ * The counter is updated in asynchronous manner
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+ * and may become negative, see:
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+ * include/linux/mm.h: get_mm_counter()
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+ */
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+ if (count > 0)
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+ rss += count;
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+
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+ count = LONG(tt->mm_struct +
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OFFSET(mm_struct_rss_stat) +
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OFFSET(mm_rss_stat_count) +
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(anonpages * sizeof(long)));
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+ if (count > 0)
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+ rss += count;
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}
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/* Check whether SPLIT_RSS_COUNTING is enabled */
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@@ -4769,7 +4780,8 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
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RETURN_ON_ERROR))
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continue;
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- rss_cache += sync_rss;
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+ if (sync_rss > 0)
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+ rss_cache += sync_rss;
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/* count 1 -> anonpages */
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if (!readmem(first->task +
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@@ -4782,7 +4794,8 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
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RETURN_ON_ERROR))
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continue;
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- rss_cache += sync_rss;
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+ if (sync_rss > 0)
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+ rss_cache += sync_rss;
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if (first == last)
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break;
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--
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2.37.1
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