File 6013e4bd-memory-bail-from-page-scrub-when-CPU-o... of Package xen

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File 6013e4bd-memory-bail-from-page-scrub-when-CPU-offline.patch of Package xen (Revision e9ac4ee16b40904e10e4d16a323a95b9)

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# Commit 3c9fd69416f8ffc611705fb24dfb383203ddc84f
# Date 2021-01-29 11:34:37 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
memory: bail from page scrubbing when CPU is no longer online

Scrubbing can significantly delay the offlining (parking) of a CPU (e.g.
because of booting into in smt=0 mode), to a degree that the "CPU <n>
still not dead..." messages logged on x86 in 1s intervals can be seen
multiple times. There are no softirqs involved in this process, so
extend the existing preemption check in the scrubbing logic to also exit
when the CPU is no longer observed online.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1324,9 +1324,11 @@ bool scrub_free_pages(void)
                      * Scrub a few (8) pages before becoming eligible for
                      * preemption. But also count non-scrubbing loop iterations
                      * so that we don't get stuck here with an almost clean
-                     * heap.
+                     * heap. Consider the CPU no longer being seen as online as
+                     * a request to preempt immediately, to not unduly delay
+                     * its offlining.
                      */
-                    if ( cnt > 800 && softirq_pending(cpu) )
+                    if ( !cpu_online(cpu) || (cnt > 800 && softirq_pending(cpu)) )
                     {
                         preempt = true;
                         break;

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File 6013e4bd-memory-bail-from-page-scrub-when-CPU-offline.patch of Package xen (Revision e9ac4ee16b40904e10e4d16a323a95b9)

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