@goodbest 好吧,我错了,倒也没人云亦云,只怪我理解错误,中午还和同事盘算去杭州买5K iMac,兴奋过度.

杭州新店去买,浙江省保修三年,如果你近的话.

@xenme 虚拟化的最终目的就是要压榨CPU和系统性能，在保证系统正常运作的情况下，少花钱多办事。大多数情况都用不到50%说明你对项目的评估和设备的采购选型不对称，或者是你不差钱，但是看你所说的这些都是建立在在你的LAB里面创建VM的情况下的，没有实际的”业务“在跑。虚拟化的目的不是为了创建VM而虚拟化。除非你是做小鸡生意的，超卖的话想创建几个VM创建几个，但是对于用户来说，性能就一塌糊涂了。

就算会也承认自己不会，怕被骂搞IT的不会修XX丢人？那你还是继续去支持吧。。。。

@xenme When a world migrates away from the source pCPU, where it has run awhile and brought instructions and data (the working set*) into the on-chip cache, the world has to bring the working set back into the cache†of the destination pCPU.

假设60M的一个world，15M on-chip cache需要migrate 4次，20M on-chip cache需要migrate 3次，L5520需要migrate 7.5次，那是不是cache越大migration越少，性能越高呢？

@myliyifei 经验，文档应该也有的吧，但是首先要确定你自己要跑什么服务，你拿它来做存储服务的话CPU当然不要紧，vCPU本来就一直处于Idle状态，不需要调配。 如果是CPU要求高的服务那这个cache对性能影响很关键。

随便找了一个
http://www.vmware.com/files/pdf/techpaper/VMware-vSphere-CPU-Sched-Perf.pdf

----------------------------
Load Balancing
ESXi is typically deployed on multiprocessor systems. On multiprocessor systems, balancing CPU load across
processors, or load balancing, is critical to the performance. Load balancing is achieved by having a world migrate
from a busy pCPU to a less loaded pCPU. Generally, the world migration improves the responsiveness of a system
and its overall CPU utilization.
Consider a system that has only two pCPUs, where a number of worlds are ready to run on one pCPU while none
on the other. Without load balancing, such imbalance would persist. As a result, the ready worlds accrue
unnecessary scheduling latency and the CPU utilization becomes only half of what could be attainable.
On ESXi, the world migration can be initiated by either a pCPU, which becomes idle, or a world, which becomes
ready to be scheduled. The former is also referred to as pull migration while the latter is referred to as push
migration. With these migration policies, ESXi achieves high utilization and low scheduling latency.
The cost of world migration is also carefully evaluated when making a migration decision. When a world migrates
away from the source pCPU, where it has run awhile and brought instructions and data (the working set*
) into the
on-chip cache, the world has to bring the working set back into the cache†
of the destination pCPU. For a
workload that benefits from caching, frequent migrations can be detrimental.
There are many other factors that need to be considered to make optimal scheduling decision. In vSphere 5.x, the
goodness load balancing algorithm is introduced.

L2-L3对多VM的ESXi性能影响蛮大的，关系到vCPU的load balancing，vCPU都是share的L2-L3的缓存，用它们来做CPU资源的迁移，当然也有LLC调内存处理权重低的作业。

如果你的服务不涉及大CPU负载的话15和20MB的缓存区别不会太明显。

但是对于CPU需求高的服务，最明显的一点，对于我自己的一个vcenter cluster，相同内存，主频类似的几个host，host所跑的负载也类似，缓存少的那几台host上的VM更多的报CPU usage不足的警告。

http://i.imgur.com/CHgSmAt.png

感觉按照歌曲名称推荐的权重比按照歌曲种类年份语言的权重还要高

屏蔽整个阿里IP段没有任何报告的路过.

说错了,租的是20楼,砍人的是21楼.

像当年Google刚进中国的时候,在上海的世纪商贸广场21楼租了几间小办公室,没几天楼上持械斗殴,砍刀乱砍,把电梯都染红了.

@GavinMa 你确定你有1万个用户需要开1万个端口么,我只做过面向服务的连接数和流量限制,比如web的http(s),SSH的22. 就像楼上所说,你的需求用connlimit做源地址的限制比较合理,当然你可以写一万条防火墙脚本,这么长的脚本我就没法说保证系统的效率了,不过你也可以试一下.

Silicom 双Gig

@8748 突然对河南的消费能力刮目相看，一直以为水果应该在山西开店。。。。