Messages in this thread | | | From | "Shi, Alex" <> | Date | Tue, 3 Nov 2009 22:42:03 +0800 | Subject | kernel building regression on 32-rc5 kernel |
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I found the kernel building will have about 20%~ 30% regressions on our NHM machines. My kernel build do the following things 15 times: make mrproper; echo \"3\">/proc/sys/vm/drop_caches; make defconfig; make -j${2timescpunumbers} Bisect found it is due to the commitment: commit a6151c3a5c8e1ff5a28450bc8d6a99a2a0add0a7 Author: Jens Axboe <jens.axboe@oracle.com> Date: Wed Oct 7 20:02:57 2009 +0200 cfq-iosched: apply bool value where we return 0/1
It quite makes me confused, but after reverting this patch the performance recovered. I analyzed the vmstat and "perf record" results, But did not find something strange. Just the "perf stat" shows something different.
Perf stat output of Rc5 kernel:
850121.335684 task-clock-msecs # 1.035 CPUs 867280 context-switches # 0.001 M/sec 266319 CPU-migrations # 0.000 M/sec 76663435 page-faults # 0.090 M/sec 2697372004020 cycles # 3172.926 M/sec (scaled from 100.00%) 2779762582367 instructions # 1.031 IPC (scaled from 100.00%) 14230675659 cache-references # 16.740 M/sec (scaled from 100.00%) 3048368747 cache-misses # 3.586 M/sec (scaled from 100.00%) 821.432570507 seconds time elapsed
Perf stat output of rc5 without the commit kernel: 900054.808787 task-clock-msecs # 1.237 CPUs 845152 context-switches # 0.001 M/sec 252689 CPU-migrations # 0.000 M/sec 77495232 page-faults # 0.086 M/sec 2470286471361 cycles # 2744.596 M/sec 2684134677043 instructions # 1.087 IPC 14685367142 cache-references # 16.316 M/sec 2869381827 cache-misses # 3.188 M/sec 727.415980216 seconds time elapsed
BRG Alex
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