Meta is saving millions of dollars thanks to this clever memory hack
Transparent memory offloading (TMO) saves up to almost a third of memory per server
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Engineers at Meta, Facebook’s parent company, have revealed how they have been able to offer free memory using a software solution called Transparent Memory Offloading (TMO).
It is now part of theLinuxkernel and, in a nutshell, automatically offloads data to other storage tiers (e.g.Samsung’s CX memory expander) that are less costly and more power efficient than memory.
The savings are significant; TMO has been running on millions of Facebookserversfor more than a year, saving up to almost a third of memory per server. While that is likely to be insignificant across dozens or even hundreds of servers,Facebook’s immense scale presents a unique challenge.
Analysis: Facebook’s gargantuan appetite for RAM
The world’s largest social network has nearly three billion monthly active users and millions of servers spread around 21 locations worldwide. Should each server carry 128GB of RAM on average, that would amount to 256 million GB (or 256PB) ofRAMwhich, at an average cost of $4 per GB (DDR4 ECC RAM), is about $1 billion worth of memory. That’s on the assumption that Facebook has at least two million servers (Facebook’s blog quoted “millions of servers” as early as July 2018), with the real number likely to be far higher.
Numbers presented by the team that worked on TMO showed that the cost of memory accounts for a third of Meta’s server bill of materials, with compressed RAM and SSD accounting for less than 11%. More worryingly, the cost burden of RAM (as a percentage of the total infrastructure) has more than doubled since Facebook launched its first generation of servers (it’s currently on the fourth).
Adopting TMO does come with some drawbacks; most notably, a degradation in performance. But the gains in terms of power and memory savings, far, far outweigh the disadvantages and future iterations combined with hardware improvements (e.g. fasterSSDor CXL drives) will offer further mitigation.
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Désiré has been musing and writing about technology during a career spanning four decades. He dabbled inwebsite buildersandweb hostingwhen DHTML and frames were in vogue and started narrating about the impact of technology on society just before the start of the Y2K hysteria at the turn of the last millennium.
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