不知大家最近是否有发现，收藏夹已经偷偷的在改版了哦～～本次改版包括2部分内容：收藏步骤的改动和收藏宝贝detail中关联推荐的内容优化。

        我们就按照收藏的过程来综合看下这次改动后的结果吧。

        首先，用户在完成收藏这个动作之后，会跳出一个对话框（如下图），包括4块内容。

1. 已有216位收藏成功啦–收藏成功的提示
2. 淘宝猜你还喜欢–点击此链接到达该被收藏商品的关联推荐页面。（具体页面请继续向下看）
3. 查看我的收藏夹–点击此链接到达我的收藏list。（此页面暂时未改动，敬请期待下次改版！是不是有句叫“且听下回分解”哈哈）
4. 本类销售热门排行榜–虽然叫做了这个名字（为了吸引用户点击），其实推荐的内容是和当前收藏的商品具有相关性并且在同一类目下的商品。因为当你做收藏这个动作而非没有购买动作的时候，我们认为你对该类商品有兴趣，但可能还要多比较些同类商品，才能让你下决心去购买，所以我们在此时推荐同类商品给你，方便你更快的找到自己真正心仪的商品。点击此热门排行榜中推荐商品的链接，到达该商品的收藏关联推荐页面。

        提到了2次收藏关联推荐页面，大家一定很好奇，到底页面是怎样的呢？现在就来详细解说吧。

        收藏关联推荐页面一共分为五个部分：

        第一部分，用户关注商品的简要信息。上图先，

        这是用户所点击商品的一个简要信息。用户可以通过点击图片和最上方的文字链接到该商品的detail页面，可是在detail中查看商品详情，并且进行购买的操作。

        第二部分，同类商品推荐。请看下图，

        用户关注某件商品，肯定是对某类商品感兴趣或者有购买意向，所以我们给出同类的8件商品，让用户可以在这8件同类商品中，方便的进行比较和挑选。以便让用户更快的找到目标商品而做出购买决策。同时，点击图片和商品标题文字均可到达商品detail页面。用户可以对感兴趣的商品进行详细的了解并购买。

        与此同时，我们还提供了非同类的一个推荐。请看第三部分：

        用户除了可以看到同类的相关商品之外，还可以看到在别的不同类别下的相关商品。这样可以扩展用户的兴趣，让用户看到更多可能感兴趣的东西。就例如刚刚那个《无框画挂钟》，一般看这类商品的都是一些正在装饰新家的女用户，所以在我们给他的非同类的商品中还有：搁架、床单、挂帘、画等。又因为用户为女性，所以可能她会同时看一些服饰、鞋帽等，来满足自己的购物欲，所以这些就是我们给予看该《无框画挂钟》所推荐的商品。

        用户可以通过点击商品图片和商品标题，到达商品detail页面来进行购买和继续收藏。

        第四部分：相关店铺推荐，如下图，

        如果用户的行为习惯是看某个卖家店铺的，也可以通过对店铺的推荐，让用户通过点击店标和店铺名来快速到达我们所推荐的店铺。根据用户浏览的商品，我们根据算法给出的推荐店铺有专卖无框画钟的店铺，也有其他装饰店铺，也有其他服饰类等来满足用户的各类需求。

        第五部分：该类下排行榜，如下图，

        用户可以通过排行榜信息很快的了解到该类目下，哪些商品最热门，价格是多少。用户可以直接点击图片和商品链接到达商品detail页面上，直接进行购买。满足某些喜欢看排行的用户的需求。

        以上就是收藏的整个过程和页面展现。大家感兴趣的可以立即去淘宝网收藏一个商品看看哦！希望大家都能在淘宝找到自己喜欢的宝贝哦～

        如果大家对收藏店铺也感兴趣的，且听下回分解了！哈哈。

So you’re running dedicated MySQL Linux box with plenty of memory, so the good question arises if you should have swap file enabled or disable it ? I’ve seen production successfully running on boxes both with and without swap file so it is not the question of you must do it this or that way but rather understanding advantages of both approaches.

I also would like to hear what you do yourself, and why

The rationale behind disabling swap is what there is nothing you want to swap out on such box anyway and if you disable swap file kernel will not swap and possibly will be able to manage memory smarter knowing it does not need to look for pages to swap out or balance memory for reducing a cache or swapping something out.

And indeed if you run with swap disabled you would not have the issue of swapping happening on the box as there is just nowhere to swap.

So what is about enabled swap - if we assume the kernel is smart (as we did for second case) we will be able to save a bit of memory as there are some programs which are started but never never really used. These would be first valid candidates to swap out. Second if you have swap file you get a bit more flexibility. What happens if you miscounted something or there is a gotcha in your application and you ended up with a lots of connections creating large temporary tables and so MySQL running out of memory (and getting killed by kernel). It could not even be MySQL but some script cron script or something similar with same affect.

In practice there are additional issues for both of the configurations - if you keep swap enabled you may have hard time keeping MySQL in memory because Kernel would love to swap it out. Recent kernels become much better than few years ago but I still run in workloads which expose bad kernel behavior and swap buffer space out even with /proc/sys/vm/swappiness =0. You can lock MySQL in memory by using –memlock option but it opens its own can of worms.

If you keep swap disabled you can run into another problems. A lot of code in the kernel assumes there is a swap space and I’ve seen kernel starting to behave crazy when there is memory pressure and there is nothing to swap out. This may actually mean the buffer pool (or other caches) which you can safely use can be less if you have swap file disabled. Though I must note again this can be workload and kernel version specific.

Besides general considerations there are many case specific ones. For example if you would rather spend more memory (allowing more reserve for spikes) than to have slowdown caused by swapping activities in case memory overcommit occurs you may be better off without swap file. If on the contrary you want to use as much memory as possible to get last bit of performance and do not mind slowdowns if you mixedup as well as have tools to resolve them quickly (ie killing runaway queries) keeping swap file enabled may be right for you.

Myself I tend to keep swap enabled on MySQL server but of course ensure there is not swapping happening (si/so columns in VMSTAT are zero or close to zero).

If you want to keep swap file disabled that also fine but you should make sure your workload is stable so there are no large spikes in memory requirements, as well as you have processes and discipline to make sure it is kept stable.

Entry posted by peter | 8 comments

Add to: | | | |

So you’re running dedicated MySQL Linux box with plenty of memory, so the good question arises if you should have swap file enabled or disable it ? I’ve seen production successfully running on boxes both with and without swap file so it is not the question of you must do it this or that way but rather understanding advantages of both approaches.

I also would like to hear what you do yourself, and why

The rationale behind disabling swap is what there is nothing you want to swap out on such box anyway and if you disable swap file kernel will not swap and possibly will be able to manage memory smarter knowing it does not need to look for pages to swap out or balance memory for reducing a cache or swapping something out.

And indeed if you run with swap disabled you would not have the issue of swapping happening on the box as there is just nowhere to swap.

So what is about enabled swap - if we assume the kernel is smart (as we did for second case) we will be able to save a bit of memory as there are some programs which are started but never never really used. These would be first valid candidates to swap out. Second if you have swap file you get a bit more flexibility. What happens if you miscounted something or there is a gotcha in your application and you ended up with a lots of connections creating large temporary tables and so MySQL running out of memory (and getting killed by kernel). It could not even be MySQL but some script cron script or something similar with same affect.

In practice there are additional issues for both of the configurations - if you keep swap enabled you may have hard time keeping MySQL in memory because Kernel would love to swap it out. Recent kernels become much better than few years ago but I still run in workloads which expose bad kernel behavior and swap buffer space out even with /proc/sys/vm/swappiness =0. You can lock MySQL in memory by using –memlock option but it opens its own can of worms.

If you keep swap disabled you can run into another problems. A lot of code in the kernel assumes there is a swap space and I’ve seen kernel starting to behave crazy when there is memory pressure and there is nothing to swap out. This may actually mean the buffer pool (or other caches) which you can safely use can be less if you have swap file disabled. Though I must note again this can be workload and kernel version specific.

Besides general considerations there are many case specific ones. For example if you would rather spend more memory (allowing more reserve for spikes) than to have slowdown caused by swapping activities in case memory overcommit occurs you may be better off without swap file. If on the contrary you want to use as much memory as possible to get last bit of performance and do not mind slowdowns if you mixedup as well as have tools to resolve them quickly (ie killing runaway queries) keeping swap file enabled may be right for you.

Myself I tend to keep swap enabled on MySQL server but of course ensure there is not swapping happening (si/so columns in VMSTAT are zero or close to zero).

If you want to keep swap file disabled that also fine but you should make sure your workload is stable so there are no large spikes in memory requirements, as well as you have processes and discipline to make sure it is kept stable.

Entry posted by peter | 8 comments

Add to: | | | |

©作者：eygle 发布在 eygle.com

今天从新东方回来，在小区门口，遇到了孟静同学。

这是我搬到这里来之后，第二次遇到疑似孟静同学，临近的时候，我打声招呼：是孟静么?
她稍微有点一愣，然后说：是啊，你是?

我说：是你的fans，你上过我的网站，我也经常读你的网站，但是我们是第一次见面。
然后她开始猜测我说MSN上的某个陌生人，或者曾经某次在公交车上遇到过。

我说：都不是（可是我们有颇深的渊源）....
我说：也许以后有机会去打扰你，我们住一个小区
她说：你住几号楼？
我说：7号
他说：哦，10号
我说：不是，是7号

孟同学说，我给你一张名片吧，也许以后可以联络。
我看她游忽不定的心神，说bye-bye。

忽然想起怀里抱着刚买的玫瑰和百合，转过身来喊住她说：孟静，我送你一只玫瑰好吧？
孟MM说：不要，因为我要去看戏。

会话到此结束。回家被老婆教训一顿，以后再不敢乱送花了，汗ing。

关于孟静是谁，请参考：孟静其人，孟八，我和老婆是这样认识的....

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