Re: [PATCH] dcache: Translating dentry into pathname without takingrename_lock

From: John Stoffel
Date: Wed Sep 04 2013 - 17:04:12 EST


>>>>> "Waiman" == Waiman Long <waiman.long@xxxxxx> writes:

Waiman> In term of AIM7 performance, this patch has a performance boost of
Waiman> about 6-7% on top of Linus' lockref patch on a 8-socket 80-core DL980.

Waiman> User Range | 10-100 | 200-10000 | 1100-2000 |
Waiman> Mean JPM w/o patch | 4,365,114 | 7,211,115 | 6,964,439 |
Waiman> Mean JPM with patch | 3,872,850 | 7,655,958 | 7,422,598 |
Waiman> % Change | -11.3% | +6.2% | +6.6% |

This -11% impact is worisome to me, because at smaller numbers of
users, I would still expect the performance to go up. So why the big
drop?

Also, how is the impact of these changes on smaller 1 socket, 4 core
systems? Just because it helps a couple of big boxes, doesn't mean it
won't hurt the more common small case.

John
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