Messages in this thread | | | Date | Mon, 10 Aug 2009 14:06:02 +0530 | From | Balbir Singh <> | Subject | Re: Help Resource Counters Scale Better (v3) |
| |
* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-08-10 15:22:05]:
> On Mon, 10 Aug 2009 14:45:59 +0900 > KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > > > > Do you agree? > > > > Ok. Config is enough at this stage. > > > > The last advice for merge is, it's better to show the numbers or > > ask someone who have many cpus to measure benefits. Then, Andrew can > > know how this is benefical. > > (My box has 8 cpus. But maybe your IBM collaegue has some bigger one) > > > > In my experience (in my own old trial), > > - lock contention itself is low. not high. > > - but cacheline-miss, pingpong is very very frequent. > > > > Then, this patch has some benefit logically but, in general, > > File-I/O, swapin-swapout, page-allocation/initalize etc..dominates > > the performance of usual apps. You'll have to be careful to select apps > > to measure the benfits of this patch by application performance. > > (And this is why I don't feel so much emergency as you do) > > > > Why I say "I want to see the numbers" again and again is that > this is performance improvement with _bad side effect_. > If this is an emergent trouble, and need fast-track, which requires us > "fix small problems later", plz say so. >
OK... I finally got a bigger machine (24 CPUs). I ran a simple program called parallel_pagefault, which does pagefault's in parallel (runs on every other CPU) and allocates 10K pages and touches the data allocated, unmaps and repeats the process. I ran the program for 300 seconds. With the patch, I was able to fault in twice the number of pages as I was able to without the patch. I used perf tool from tools/perf in the kernel
With patch
Performance counter stats for '/home/balbir/parallel_pagefault':
7188177.405648 task-clock-msecs # 23.926 CPUs 423130 context-switches # 0.000 M/sec 210 CPU-migrations # 0.000 M/sec 49851597 page-faults # 0.007 M/sec 5900210219604 cycles # 820.821 M/sec 424658049425 instructions # 0.072 IPC 7867744369 cache-references # 1.095 M/sec 2882370051 cache-misses # 0.401 M/sec
300.431591843 seconds time elapsed
Without Patch
Performance counter stats for '/home/balbir/parallel_pagefault':
7192804.124144 task-clock-msecs # 23.937 CPUs 424691 context-switches # 0.000 M/sec 267 CPU-migrations # 0.000 M/sec 28498113 page-faults # 0.004 M/sec 5826093739340 cycles # 809.989 M/sec 408883496292 instructions # 0.070 IPC 7057079452 cache-references # 0.981 M/sec 3036086243 cache-misses # 0.422 M/sec
300.485365680 seconds time elapsed
-- Balbir
| |