The strict setting also comes with noted performance penalties. I will also test sync_binlog=1000 and sync_binlog=10000, which means perform synchronous writes of binary logs every 1000 and 10000 transactions, respectively.
第二篇則是拿 MySQL 8.0 與 Percona Server 5.7 比較，可以發現在 MySQL 8.0 開啟 binlog 時有時會有不少的效能損失：
It seems that binary logs have quite an effect MySQL 8.0, and we see up to a 30% performance penalty as opposed to the 13% for Percona Server for MySQL 5.7.
原因是 Linux 與 OS X 上有 direct-physical map 的機制，會把整塊 physical memory 對應到 virtual memory 的固定位置上，這些位置不會再發給 user space 使用，所以是通的：
On Linux and OS X, this is done via a direct-physical map, i.e., the entire physical memory is directly mapped to a pre-defined virtual address (cf. Figure 2).
而在 Windows 上則是比較複雜，但大部分的 physical memory 都有對應到 kernel address space，而每個 process 裡面也都還是有完整的 kernel address space (只是受到權限控制)，所以 Meltdown 的攻擊仍然有效：
Instead of a direct-physical map, Windows maintains a multiple so-called paged pools, non-paged pools, and the system cache. These pools are virtual memory regions in the kernel address space mapping physical pages to virtual addresses which are either required to remain in the memory (non-paged pool) or can be removed from the memory because a copy is already stored on the disk (paged pool). The system cache further contains mappings of all file-backed pages. Combined, these memory pools will typically map a large fraction of the physical memory into the kernel address space of every process.
FLUSH+RELOAD 是希望透過 shared memory & cache 得到 side channel information，藉此突破安全機制。
論文裡面提到兩個攻擊模式，一種是在同一個 OS 裡面 (same-OS)，另外一種是在同一台機器，但是是兩個不同的 VM (cross-VM)。攻擊的前提是要拿到與 GnuPG process 相同的 shared memory。兩個環境的作法都是透過 mmap() GnuPG 的執行檔以取得 shared memory。
在 same-OS 的情況下會使用同一個 process：
To achieve sharing, the spy mmaps the victim’s executable file into the spy’s virtual address space. As the Linux loader maps executable files into the process when executing them, the spy and the victim share the memory image of the mapped file.
For the cross-VM scenario we used two different hypervisors: VMware ESXi 5.1 on the HP machine and Centos 6.5 with KVM on the Dell machine. In each hypervisor we created two virtual machines, one for the victim and the other for the spy. The virtual machines run CentOS 6.5 Linux. In this scenario, the spy mmaps a copy of the victim’s executable file. Sharing is achieved through the page de-duplication mechanisms of the hypervisors.
We demonstrate the efficacy of the FLUSH+RELOAD attack by using it to extract the private encryption keys from a victim program running GnuPG 1.4.13. We tested the attack both between two unrelated processes in a single operating system and between processes running in separate virtual machines. On average, the attack is able to recover 96.7% of the bits of the secret key by observing a single signature or decryption round.
