)]}'
{
  "commit": "902aaed0d983dfd459fcb2b678608d4584782200",
  "tree": "00b18597d87101ba1b37e5dcfde1d91312870160",
  "parents": [
    "754af6f5a85fcd1ecb456851d20c65e4c6ce10ab"
  ],
  "author": {
    "name": "Hisashi Hifumi",
    "email": "hifumi.hisashi@oss.ntt.co.jp",
    "time": "Tue Oct 16 01:24:52 2007 -0700"
  },
  "committer": {
    "name": "Linus Torvalds",
    "email": "torvalds@woody.linux-foundation.org",
    "time": "Tue Oct 16 09:42:54 2007 -0700"
  },
  "message": "mm: use pagevec to rotate reclaimable page\n\nWhile running some memory intensive load, system response deteriorated just\nafter swap-out started.\n\nThe cause of this problem is that when a PG_reclaim page is moved to the tail\nof the inactive LRU list in rotate_reclaimable_page(), lru_lock spin lock is\nacquired every page writeback .  This deteriorates system performance and\nmakes interrupt hold off time longer when swap-out started.\n\nFollowing patch solves this problem.  I use pagevec in rotating reclaimable\npages to mitigate LRU spin lock contention and reduce interrupt hold off time.\n\nI did a test that allocating and touching pages in multiple processes, and\npinging to the test machine in flooding mode to measure response under memory\nintensive load.\n\nThe test result is:\n\n\t-2.6.23-rc5\n\t--- testmachine ping statistics ---\n\t3000 packets transmitted, 3000 received, 0% packet loss, time 53222ms\n\trtt min/avg/max/mdev \u003d 0.074/0.652/172.228/7.176 ms, pipe 11, ipg/ewma\n17.746/0.092 ms\n\n\t-2.6.23-rc5-patched\n\t--- testmachine ping statistics ---\n\t3000 packets transmitted, 3000 received, 0% packet loss, time 51924ms\n\trtt min/avg/max/mdev \u003d 0.072/0.108/3.884/0.114 ms, pipe 2, ipg/ewma\n17.314/0.091 ms\n\nMax round-trip-time was improved.\n\nThe test machine spec is that 4CPU(3.16GHz, Hyper-threading enabled)\n8GB memory , 8GB swap.\n\nI did ping test again to observe performance deterioration caused by taking\na ref.\n\n\t-2.6.23-rc6-with-modifiedpatch\n\t--- testmachine ping statistics ---\n\t3000 packets transmitted, 3000 received, 0% packet loss, time 53386ms\n\trtt min/avg/max/mdev \u003d 0.074/0.110/4.716/0.147 ms, pipe 2, ipg/ewma 17.801/0.129 ms\n\nThe result for my original patch is as follows.\n\n\t-2.6.23-rc5-with-originalpatch\n\t--- testmachine ping statistics ---\n\t3000 packets transmitted, 3000 received, 0% packet loss, time 51924ms\n\trtt min/avg/max/mdev \u003d 0.072/0.108/3.884/0.114 ms, pipe 2, ipg/ewma 17.314/0.091 ms\n\nThe influence to response was small.\n\n[akpm@linux-foundation.org: fix uninitalised var warning]\n[hugh@veritas.com: fix locking]\n[randy.dunlap@oracle.com: fix function declaration]\n[hugh@veritas.com: fix BUG at include/linux/mm.h:220!]\n[hugh@veritas.com: kill redundancy in rotate_reclaimable_page]\n[hugh@veritas.com: move_tail_pages into lru_add_drain]\nSigned-off-by: Hisashi Hifumi \u003chifumi.hisashi@oss.ntt.co.jp\u003e\nSigned-off-by: Andrew Morton \u003cakpm@linux-foundation.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@linux-foundation.org\u003e\n",
  "tree_diff": [
    {
      "type": "modify",
      "old_id": "d93fa1e9ec7c8b9e2b7b4d7407de35577fd4dfb7",
      "old_mode": 33188,
      "old_path": "mm/swap.c",
      "new_id": "d034b2128d2b09d5182e724a4e655a97804803d0",
      "new_mode": 33188,
      "new_path": "mm/swap.c"
    }
  ]
}