68 lines
2.6 KiB
Diff
68 lines
2.6 KiB
Diff
From b3af265aa60251f282145bb0eee3b83d8a15ebb7 Mon Sep 17 00:00:00 2001
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From: HATAYAMA Daisuke <d.hatayama@fujitsu.com>
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Date: Mon, 18 Sep 2023 20:45:11 -0400
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Subject: [PATCH 2/2] x86: fix extend gcore.so taking much time like more than
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1 hour when huge thread group is present
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extend gcore.so command takes lengthy time such as more than 1 hour
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when huge thread group is present.
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The root cause of this issue is that we never take into account time
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complexity of function gcore_arch_vsyscall_has_vm_alwaysdump_flag()
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sufficiently, which iterates the task list and vma lists of each task
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to detect existence of VM_ALWAYS flag in a given crash dump and so has
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O(nm) where the n is the length of the task list and the m is the
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total number of vma among all tasks.
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To fix this issue, skip this process for the kernels whose version is
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equal to or larger than v3.4.0.
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Originally, this process was implemented to detect existence of
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VM_ALWAYS flag that was removed at the commit
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909af768e88867016f427264ae39d27a57b6a8ed (coredump: remove
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VM_ALWAYSDUMP flag) included at Linux kernel v3.4. However, the base
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kernel version of RHEL7.0 GA is 3.10.0-123.el7. Hence, the kernels for
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RHEL7 and later have included the commit. For RHEL7 and later, it's
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sufficient to conclude absence of the flag by checking kernel version
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of a given crash dump.
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The issue could still remain on RHEL6 and older, but we think it's
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acceptable because today we rarely handle crash dump files of RHEL6
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and older.
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Signed-off-by: HATAYAMA Daisuke <d.hatayama@fujitsu.com>
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Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
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---
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src/libgcore/gcore_x86.c | 15 +++++++++++++++
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1 file changed, 15 insertions(+)
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diff --git a/src/libgcore/gcore_x86.c b/src/libgcore/gcore_x86.c
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index 8878f79d4c08..3ddf5109ade0 100644
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--- a/src/libgcore/gcore_x86.c
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+++ b/src/libgcore/gcore_x86.c
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@@ -2502,6 +2502,21 @@ int gcore_arch_vsyscall_has_vm_alwaysdump_flag(void)
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struct task_context *tc;
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int i;
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+ /*
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+ * The commit 909af768e88867016f427264ae39d27a57b6a8ed
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+ * (coredump: remove VM_ALWAYSDUMP flag) of the Linux kernel
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+ * was merged at v3.4. We can say VM_ALWAYSDUMP flag doesn't
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+ * exist for the version 3.4.0 or later. The base kernel
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+ * version of RHEL7.0 GA is 3.10.0-123.el7. Hence, this
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+ * condition is expected to match RHEL7 and later RHEL major
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+ * versions. On the other hand, the commit
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+ * 909af768e88867016f427264ae39d27a57b6a8ed was backported
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+ * into the kernel package in RHEL6 and the exploring code is
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+ * still needed.
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+ */
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+ if (THIS_KERNEL_VERSION >= LINUX(3, 4, 0))
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+ return FALSE;
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+
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/*
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* For simplicity, consider that VM_ALWAYSDUMP was already not
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* present when maple tree was introduced.
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--
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2.45.1
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