© 2024 Bloomberg Finance L.P.© 2024 Bloomberg Finance L.P. What’s Eating My RAM? CppCon 2024 September 17, 2024 Jianfei Pan Software Engineer, Portfolio/Risk AnalyticsA story 🚨 90% Memory Used: What’s

might the standard help us in future?AGENDA • Sub-megabyte days • More RAM, more disk capacity • Moving data into and out of RAM • File IO in C++ from fstream to the OS SDK • The 64-bit address spaceSUB-MEGABYTE DAYSMORE RAM, MORE DISK CAPACITY • Picture of a 44MB hard diskMORE RAM, MORE DISK CAPACITYMORE RAM, MORE DISK CAPACITY • FAT16MORE RAM, MORE DISK CAPACITY • FAT16 • File Allocation TableMORE RAM, MORE • FAT16 • File Allocation Table • Root directoryMORE RAM, MORE DISK CAPACITY • FAT16 • File Allocation Table • Root directory • EntryMORE RAM, MORE DISK CAPACITY • FAT16 • File Allocation Table

ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 7 ROOTDEV ?= /dev/mmcblk0 8 [ aarch64/virt ]: 9 ARCH = arm64 10 CPU ?= cortex-a57 11 LINUX ?= v5.1 12 ROOTDEV_LIST := /dev/sda /dev/vda /dev/ram0 /dev/nfs 13 ROOTDEV /dev/ram0 /dev/nfs 19 ROOTDEV ?= /dev/mmcblk0 20 [ arm/versatilepb ]: 21 ARCH = arm 22 CPU ?= arm926t 23 LINUX ?= v5.1 24 ROOTDEV_LIST := /dev/sda /dev/ram0 /dev/nfs 25 ROOTDEV ?= /dev/ram0 26 ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 /dev/nfs 31 ROOTDEV ?= /dev/ram0 32 [ i386/pc ]: 33 ARCH = x86 34 CPU ?= qemu32 35 LINUX ?= v5.1 36 ROOTDEV_LIST ?= /dev/hda /dev/ram0 /dev/nfs 37 ROOTDEV_LIST[LINUX_v2

ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 7 ROOTDEV ?= /dev/mmcblk0 8 [ aarch64/virt ]: 9 ARCH = arm64 10 CPU ?= cortex-a57 11 LINUX ?= v5.1 12 ROOTDEV_LIST := /dev/sda /dev/vda /dev/ram0 /dev/nfs 13 ROOTDEV /dev/ram0 /dev/nfs 19 ROOTDEV ?= /dev/mmcblk0 20 [ arm/versatilepb ]: 21 ARCH = arm 22 CPU ?= arm926t 23 LINUX ?= v5.1 24 ROOTDEV_LIST := /dev/sda /dev/ram0 /dev/nfs 25 ROOTDEV ?= /dev/ram0 26 ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 /dev/nfs 31 ROOTDEV ?= /dev/ram0 32 [ i386/pc ]: 33 ARCH = x86 34 CPU ?= qemu32 35 LINUX ?= v5.1 36 ROOTDEV_LIST ?= /dev/hda /dev/ram0 /dev/nfs 37 ROOTDEV_LIST[LINUX_v2

ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 7 ROOTDEV ?= /dev/mmcblk0 8 [ aarch64/virt ]: 9 ARCH = arm64 10 CPU ?= cortex-a57 11 LINUX ?= v5.1 12 ROOTDEV_LIST := /dev/sda /dev/vda /dev/ram0 /dev/nfs 13 ROOTDEV /dev/ram0 /dev/nfs 19 ROOTDEV ?= /dev/mmcblk0 20 [ arm/versatilepb ]: 21 ARCH = arm 22 CPU ?= arm926t 23 LINUX ?= v5.1 24 ROOTDEV_LIST := /dev/sda /dev/ram0 /dev/nfs 25 ROOTDEV ?= /dev/ram0 26 ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 /dev/nfs 31 ROOTDEV ?= /dev/ram0 32 [ i386/pc ]: 33 ARCH = x86 34 CPU ?= qemu32 35 LINUX ?= v5.1 36 ROOTDEV_LIST ?= /dev/hda /dev/ram0 /dev/nfs 37 ROOTDEV_LIST[LINUX_v2

ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 7 ROOTDEV ?= /dev/mmcblk0 8 [ aarch64/virt ]: 9 ARCH = arm64 10 CPU ?= cortex-a57 11 LINUX ?= v5.1 12 ROOTDEV_LIST := /dev/sda /dev/vda /dev/ram0 /dev/nfs 13 ROOTDEV /dev/ram0 /dev/nfs 19 ROOTDEV ?= /dev/mmcblk0 20 [ arm/versatilepb ]: 21 ARCH = arm 22 CPU ?= arm926t 23 LINUX ?= v5.1 24 ROOTDEV_LIST := /dev/sda /dev/ram0 /dev/nfs 25 ROOTDEV ?= /dev/ram0 26 ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 /dev/nfs 31 ROOTDEV ?= /dev/ram0 32 [ i386/pc ]: 33 ARCH = x86 34 CPU ?= qemu32 35 LINUX ?= v5.1 36 ROOTDEV_LIST ?= /dev/hda /dev/ram0 /dev/nfs 37 ROOTDEV_LIST[LINUX_v2

ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 7 ROOTDEV ?= /dev/mmcblk0 8 [ aarch64/virt ]: 9 ARCH = arm64 10 CPU ?= cortex-a57 11 LINUX ?= v5.1 12 ROOTDEV_LIST := /dev/sda /dev/vda /dev/ram0 /dev/nfs 13 ROOTDEV /dev/ram0 /dev/nfs 19 ROOTDEV ?= /dev/mmcblk0 20 [ arm/versatilepb ]: 21 ARCH = arm 22 CPU ?= arm926t 23 LINUX ?= v5.1 24 ROOTDEV_LIST := /dev/sda /dev/ram0 /dev/nfs 25 ROOTDEV ?= /dev/ram0 26 ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 /dev/nfs 31 ROOTDEV ?= /dev/ram0 32 [ i386/pc ]: 33 ARCH = x86 34 CPU ?= qemu32 35 LINUX ?= v5.1 36 ROOTDEV_LIST ?= /dev/hda /dev/ram0 /dev/nfs 37 ROOTDEV_LIST[LINUX_v2

ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 7 ROOTDEV ?= /dev/mmcblk0 8 [ aarch64/virt ]: 9 ARCH = arm64 10 CPU ?= cortex-a57 11 LINUX ?= v5.1 12 ROOTDEV_LIST := /dev/sda /dev/vda /dev/ram0 /dev/nfs 13 ROOTDEV /dev/ram0 /dev/nfs 19 ROOTDEV ?= /dev/mmcblk0 20 [ arm/versatilepb ]: 21 ARCH = arm 22 CPU ?= arm926t 23 LINUX ?= v5.1 24 ROOTDEV_LIST := /dev/sda /dev/ram0 /dev/nfs 25 ROOTDEV ?= /dev/ram0 26 ROOTDEV_LIST := /dev/mmcblk0 /dev/ram0 /dev/nfs 31 ROOTDEV ?= /dev/ram0 32 [ i386/pc ]: 33 ARCH = x86 34 CPU ?= qemu32 35 LINUX ?= v5.1 36 ROOTDEV_LIST ?= /dev/hda /dev/ram0 /dev/nfs 37 ROOTDEV_LIST[LINUX_v2

to always set it to the correct value. 17 1 First steps 3. On the next page, select the memory (RAM) that VirtualBox should allocate every time the virtual machine is started. The amount of memory given presented to the guest operating system, which will report this size as the (virtual) computer’s installed RAM. Note: Choose this setting carefully! The memory you give to the VM will not be available to your specify more than you can spare. For example, if your host machine has 1 GB of RAM and you enter 512 MB as the amount of RAM for a particular virtual machine, while that VM is running, you will only have

48). It is therefore recommended to always set it to the correct value. 2. The amount of memory (RAM) that the virtual machine should have for itself. Every time a virtual machine is started, VirtualBox it to the guest operating system, which will report this size as the (virtual) computer’s installed RAM. Note: Choose this setting carefully! The memory you give to the VM will not be available to your specify more than you can spare. For example, if your host machine has 1 GB of RAM and you enter 512 MB as the amount of RAM for a particular virtual machine, while that VM is running, you will only have