Fresh Take On Linux Uncached Buffered I/O "RWF_UNCACHED" Nets 65~75% Improvement

[phoronix]

Phoronix: Fresh Take On Linux Uncached Buffered I/O "RWF_UNCACHED" Nets 65~75% Improvement

Linux I/O expert and block/IO_uring maintainer Jens Axboe of Meta has recently revisited his patches around uncached buffered I/O. Back in 2019 the "RWF_UNCACHED" effort was started by Axboe to address a throughput cliff in performance once the page cache fills up. That work faded away but Axboe recently took to crafting a set of fresh patches for implementing uncached buffered I/O and they are showing extremely promising results...

https://www.phoronix.com/news/Linux-RWF_UNCACHED-2024

[Danny3]

xhustler
You had to mention Axboe!

https://www.phoronix.com/forums/forum/software/general-linux-open-source/1502897-linus-torvalds-lands-a-2-6-performance-improvement-with-minor-linux-kernel-patch?p=1503163#post1503163

[jeisom]

158GB/s! I am curious about his drive setup for that. Need at least 12 PCIe5x4s nvme drives for that and saturated, unless ram disks.

[F.Ultra]

158GB/s! I am curious about his drive setup for that. Need at least 12 PCIe5x4s nvme drives for that and saturated, unless ram disks.

He wrote that it was 32 drives

[enigmaxg2]

He wrote that it was 32 drives

So, probably marginal and negligible gains for the average user.

[F.Ultra]

So, probably marginal and negligible gains for the average user.

this is just to show how well it scales. Being hit by the problems he is trying to solve is possible on a single drive.

[Soul_keeper]

It would be interesting to see a phoronix benchmark comparison with these patches.

[erniv2]

So, probably marginal and negligible gains for the average user.

This is work for Hyperscalers like Meta, where they have hundredes over hundrededs of harddrives and ssds in crasy raid setups, and if 15 lines of code can improve your read troughput by about 65% you will be crowned employee of the month and can go on vacation ....

And yes it will benifit the average user it will probably be in the range from 3-5% improvement but it helps.

In days where your average user has ssd that can give you 500 mbits even if you use a sata ssd you will see an increase of 25 mbits as conservative estimation, not to mention nvmes that run with 3gbits or pcie4 that run at 5 gbits, at 5gbits it already means a gain of 250mbits ~~.

Ah thats a general asumption ofc you cant exeed the bus speeds sata 600mbit pci3x4 4gbits pcix4x4 8gbits.

[User29]

So, probably marginal and negligible gains for the average user.

You mean desktop user? Probably yes.
But if you are a customer using some services, you'd be happy to see it's speed boosted up.

[ptrwis]

I can imagine Postgres as the first client for it