On 2024/1/13 3:25, Andrew Morton wrote:
On Fri, 12 Jan 2024 15:35:24 +0800 "Bang Li" <libang.li@xxxxxxxxxxxx> wrote:Compaction will be triggered when we write 1 to '/proc/sys/vm/ compact_memory'. During the execution of the process, when we send SIGKILL to terminate the compaction, the process does not exit immediately. Instead, it will continue to loop through the remaining zones and nodes before exiting. in my environment: [root]# cat /proc/buddyinfo Node 0, zone DMA 1 1 1 0 2 1 1 0 1 1 3 Node 0, zone DMA32 1666 1123 804 625 488 356 321 278 209 178 250 Node 0, zone Normal 58852 83160 49983 9812 2287 1229 19604 24471 10346 5219 12205 [root]# echo 1 > /sys/kernel/debug/tracing/events/compaction/mm_compaction_end/enable before the patch: [root]# timeout --signal=SIGKILL 0.002 bash -c 'echo 1 > /proc/sys/vm/compact_memory' [root]# cat /sys/kernel/debug/tracing/trace_pipe <...>-26494 [014] ..... 226.468993: mm_compaction_end: zone_start=0x1 migrate_pfn=0xe00 free_pfn=0xe00 zone_end=0x1000, mode=sync status=complete <...>-26494 [014] ..... 226.469718: mm_compaction_end: zone_start=0x1000 migrate_pfn=0x20a80 free_pfn=0xffe00 zone_end=0x100000, mode=sync status=contended <...>-26494 [014] ..... 226.469720: mm_compaction_end: zone_start=0x100000 migrate_pfn=0x100000 free_pfn=0x307fe00 zone_end=0x3080000, mode=sync status=contended after the patch: [root]# timeout --signal=SIGKILL 0.002 bash -c 'echo 1 > /proc/sys/vm/compact_memory' [root]# cat /sys/kernel/debug/tracing/trace_pipe <...>-17491 [053] ..... 109.005387: mm_compaction_end: zone_start=0x1 migrate_pfn=0xe00 free_pfn=0xe00 zone_end=0x1000, mode=sync status=complete <...>-17491 [053] ..... 109.006139: mm_compaction_end: zone_start=0x1000 migrate_pfn=0x22220 free_pfn=0xffe00 zone_end=0x100000, mode=sync status=contended Although it exits quickly after receiving the SIGKILL signal, a better solution is to terminate the loop early after receiving the SIGKILL signal.What is the use case here? The requirement? Why is this change valuable to anyone?
Thanks for the quick reply! I'm very sorry that my inappropriate use case confused you. What I want to explain is that when receiving the SIGKILL signal, we can break in advance to reduce unnecessary loops. This is a clean up patch, the purpose is to reduce the execution of unnecessary code. If possible, I will remove the confusing use case in V2. Thanks, Bang
