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Linus (又) 不爽了... XD

看得出來 Linus 對於 Intel 的行為很不爽:「Re: Avoid speculative indirect calls in kernel」。

Please talk to management. Because I really see exactly two possibibilities:

 - Intel never intends to fix anything

OR

 - these workarounds should have a way to disable them.

Which of the two is it?

那個 possibibilities 應該是 typo,但不知道為什麼看起來很有味道 XDDD

Spectre 與 Meltdown 兩套 CPU 的安全漏洞

The Register 發表了「Kernel-memory-leaking Intel processor design flaw forces Linux, Windows redesign」這篇文章,算是頗完整的說明了這次的安全漏洞 (以 IT 新聞媒體標準來看),引用了蠻多資料並且試著說明問題。

而這也使得整個事情迅速發展與擴散超出本來的預期,使得 GoogleProject Zero 提前公開發表了 Spectre 與 Meltdown 這兩套 CPU 安全漏洞。文章非常的長,描述的也比 The Register 那篇還完整:「Reading privileged memory with a side-channel」。

在 Google Project Zero 的文章裡面,把這些漏洞分成三類,剛好依據 CVE 編號分開描述:

  • Variant 1: bounds check bypass (CVE-2017-5753)
  • Variant 2: branch target injection (CVE-2017-5715)
  • Variant 3: rogue data cache load (CVE-2017-5754)

前兩個被稱作 Spectre,由 Google Project Zero、Cyberus Technology 以及 Graz University of Technology 三個團隊獨立發現並且回報原廠。後面這個稱作 Meltdown,由 Google Project Zero 與另外一個團隊獨立發現並且回報原廠。

這兩套 CPU 的安全漏洞都有「官網」,網址不一樣但內容一樣:spectreattack.commeltdownattack.com

影響範圍包括 IntelAMD 以及 ARM,其中 AMD 因為架構不一樣,只有在特定的情況下會中獎 (在使用者自己打開 eBPF JIT 後才會中):

(提到 Variant 1 的情況) If the kernel's BPF JIT is enabled (non-default configuration), it also works on the AMD PRO CPU.

這次的洞主要試著透過 side channel 資訊讀取記憶體內容 (會有一些條件限制),而痛點在於修正 Meltdown 的方式會有極大的 CPU 效能損失,在 Linux 上對 Meltdown 的修正的資訊可以參考「KAISER: hiding the kernel from user space」這篇,裡面提到:

KAISER will affect performance for anything that does system calls or interrupts: everything. Just the new instructions (CR3 manipulation) add a few hundred cycles to a syscall or interrupt. Most workloads that we have run show single-digit regressions. 5% is a good round number for what is typical. The worst we have seen is a roughly 30% regression on a loopback networking test that did a ton of syscalls and context switches.

KAISER 後來改名為 KPTI,查資料的時候可以注意一下。

不過上面提到的是實體機器,在 VM 裡面可以預期會有更多 syscall 與 context switch,於是 Phoronix 測試後發現在 VM 裡效能的損失比實體機器大很多 (還是跟應用有關,主要看應用會產生多少 syscall 與 context switch):「VM Performance Showing Mixed Impact With Linux 4.15 KPTI Patches」。

With these VM results so far it's still a far cry from the "30%" performance hit that's been hyped up by some of the Windows publications, etc. It's still highly dependent upon the particular workload and system how much performance may be potentially lost when enabling page table isolation within the kernel.

這對各家 cloud service 不是什麼好消息,如果效能損失這麼大,不太可能直接硬上 KPTI patch... 尤其是 VPS,對於平常就會 oversubscription 的前提下,KPTI 不像是可行的方案。

可以看到各 VPS 都已經發 PR 公告了 (先發個 PR 稿說我們有在注意,但都還沒有提出解法):「CPU Vulnerabilities: Meltdown & Spectre (Linode)」、「A Message About Intel Security Findings (DigitalOcean)」、「Intel CPU Vulnerability Alert (Vultr)」。

現在可以預期會有更多人投入研究,要怎麼樣用比較少的 performance penalty 來抵抗這兩套漏洞,現在也只能先等了...

蘋果對於電池的新聞稿

前幾天提到 Apple 在新版 iOS 上搞出的電池問題:「iPhone 換電池恢復效能的事情傳到 Geekbench 後...」,結果看起來是 PR 部門整個加班處理 XDDD

台灣版的公告在「致廣大顧客關於 iPhone 電池與效能的說明」這邊可以看到,英文版的則是在「A Message to Our Customers about iPhone Batteries and Performance」這邊。

前面講的都是大家都已經知道的事情了,重點在後續的部份:

  • Apple 為需要更換電池的 iPhone 6 或後續機種使用者,降低更換已過保固期的 iPhone 電池價格,從 NT$2,590 降為 NT$890,降幅為 NT$1,700。自 2018 年 1 月底至 12 月,全球同步進行。詳細優惠資訊將在近期於 apple.com/tw 公布。
  • 在 2018 年初,我們將發布一項 iOS 軟體更新,其中的新功能可為使用者更清楚顯示 iPhone 電池的健康狀態,讓他們可以自己看到電池的狀態是否影響效能。
  • Apple is reducing the price of an out-of-warranty iPhone battery replacement by $50 — from $79 to $29 — for anyone with an iPhone 6 or later whose battery needs to be replaced, starting in late January and available worldwide through December 2018. Details will be provided soon on apple.com.
  • Early in 2018, we will issue an iOS software update with new features that give users more visibility into the health of their iPhone’s battery, so they can see for themselves if its condition is affecting performance.

所以總算是能在 iPhone 上面直接看到電池的情況了...

iPhone 換電池恢復效能的事情傳到 Geekbench 後...

在「iPhone 的電池與效能」這篇提到了 iPhone 換電池可以恢復效能,結果 Geekbench (也就是原來在 Reddit 上抱怨的人用的測速軟體) 的 John Poole 從 Geekbench 的回報資料庫裡分析了資料,發現了特別的現象後寫下這篇文章 (於是後來引發一連串報導,以及 Apple 的 PR 事件):「iPhone Performance and Battery Age」。

他先拿 iPhone 6S 分析,這看起來就不太妙:

再拿 iPhone 7 的資料分析,就更確定不妙:

可以看到 iOS 的 10.2.1 與 11.2.0 有奇怪的效能集中區。

後續蘋果也確認會刻意降速:「Apple addresses why people are saying their iPhones with older batteries are running ‘slower’」。

然後最新的發展就不太意外了,開始要打架了:「Days after iPhone battery fiasco, lawsuits against Apple begin to mount」。

接下來是耶誕假期,應該要等明年才會有新消息了...

TP-Link 的 NTP 流量

在「TP-Link repeater firmware squanders 715 MB/month」這邊看到 TP-Link 因為 NTP 的關係而狂吃流量的情況:(這邊是用逗點表示小數點,所以是 715.4 MB/month)

You should probably avoid TP-Link products if you’re on a tight bandwidth budget. By design, TP-Link firmware sends six DNS requests and one NTP query every 5 seconds, for a total of 715,4 MB per month.

如果拿 24 小時都開機的 Windows 相比的話,會發現這數字天差地別:

To put this number in context: an always-on Windows device will use around 1,6 KB per month on NTP.

作者抓出韌體上面的設定,發現裡面寫死了不少伺服器... 那個 aunz 的選擇讓人頗好奇,另外直接把幾個大學的 NTP server 放進去不知道是什麼樣的想法:

TP-Link has hardcoded the following non-configurable NTP servers and server pools in their firmware:

  • time.nist.gov, time-a.nist.gov, time-b.nist.gov, time-nw.nist.gov
  • au.pool.ntp.org, nz.pool.ntp.org
  • 133.100.9.2, 128.138.140.44, 192.36.144.22

The first sets of servers are operated by the US National Institute of Standards and Technology (NIST). The second is the Australian and New Zealand public NTP project time server pools. The IP addresses are owned by universities in Japan, Colorado; US, and Sweden respectively.

而從行為可以看到沒有遵守這些 NTP service 的規範:

The NTP Pool project asks device manufacturers and vendors to register (and optionally sponsor) their own pools through the service (e.g. tplink.pool.ntp.org), and emphasize that they “must absolutely not use the default pool.ntp.org zone names”. They also request that vendors don’t check more often than every 5 minutes at the most.

而且因為沒有地方可以修改這些設定,唯一的解法是不要買 TP-Link 的產品:

You can avoid buying TP-Link products to avoid this problem.

You can’t turn this behavior off in TP-Link’s web administration interface nor in their management app for mobile. You can’t change the NTP server addresses it targets either.

iPhone 的電池與效能

Hacker News 上看到 Reddit 上的這則說明:「PSA: iPhone slow? Try replacing your battery!」。

他提到他的 iPhone 6S 很慢,本來以為是 iOS 11 導致的,結果發現他弟弟 (或是哥哥?) 的 iPhone 6 也是跑 iOS 11,但是快很多... 所以他就試著研究,最後決定換電池:

My iPhone 6S has been very slow these past few weeks, and even after updating multiple times, it was still slow. Couldn’t figure out why, but just thought that iOS 11 was still awful to me. Then I used my brother’s iPhone 6 Plus and his was... faster than mine? This is when I knew something was wrong. So, I did some research, and decided to replace my battery.

結果發現換電池後速度就上來了,上面這張是換電池之前,下面那張是換電池之後:

所以是在電力不足的情況下會降速?

iOS 上測試的軟體是 Geekbench 4,而官方也有給參考值 (Geekbench 的),在 iOS Benchmarks - Geekbench Browser 可以參考。如果在吃滿電、重開機,沒有背景的情況下還是很慢的話,有機會是類似的問題?

AWS 提昇了 Amazon EBS 能提供的效能上限

AWS 宣佈 Amazon EBS 可以提供的效能往上提高了 (這邊講的是 Provisioned IOPS SSD,代號 io1):「Amazon EBS Improves Performance for io1 Volumes」。

單一 volume 的 IOPS 從 20K 變成 32K,thoughput 從 320MB/sec 變成 500MB/sec:

Today we are announcing an improvement in performance of Provisioned IOPS SSD (io1) Volumes from 20,000 IOPS to 32,000 IOPS and from 320 MB/s to 500 MB/s of throughput per volume.

應該是科技的進步帶動的 XD

在 Ubuntu 16.04 上面隨機改變無線網卡的 MAC address

在「Randomize your WiFi MAC address on Ubuntu 16.04」這邊看到作者在介紹如何在 Ubuntu 上藉由改變無線網卡的 MAC address 保護自己的隱私:

Your device’s MAC address can be used to track you across the WiFi networks you connect to. That data can be shared and sold, and often identifies you as an individual. It’s possible to limit this tracking by using pseudo-random MAC addresses.

成果像是這樣:

主要應該是給 Ubuntu 的筆電使用者用...

Vultr 也推出 Bare Metal 的機器了

AWS 推出 Bare Metal 版本的 Instance 後 (參考「Amazon EC2 推出第一款 Bare Metal 的 Instance」),Vultr 也推出 Bare Metal 機器了:「Deploy Bare Metal Cloud Servers With Vultr!」。

目前先在新加坡推出,之後會再往其他地區推出 :

We are first introducing bare metal in Singapore and more locations will be rolled out in the coming weeks.

在「Vultr Bare Metal - Dedicated servers with hourly billing. - Vultr.com」頁可以看到目前只提供一種機器,E3-1270v6 + 32GB RAM + 2*240GB SSD,一個月 USD$300 ($0.446/hr)。

對照 AWS 提供的 E5-2686v4 + 512GB RAM + 15.2TB SSD,Vultr 的這個規格很微妙... 會有 bare metal 需求通常是因為效能上的不足,但你給的這個規格感覺就鳥鳥的,對效能的幫助好像不大啊...

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