Optimizing Linux MD Bitmap Code Yields 89% Throughput Boost For Quad SSDs

[phoronix]

Phoronix: Optimizing Linux MD Bitmap Code Yields 89% Throughput Boost For Quad SSDs

A promising patch for the Linux kernel is optimizing the locking contention and scattered address space for the MD bitmap code to improve both the storage throughput and latency...

https://www.phoronix.com/news/Optimize-Linux-MD-Bitmap-RFC

[bezirg]

Impressive... Michael bless us with such RAID benchmarks!

[fermino]

I know it is sequential throughput, but those numbers are wild nonetheless!

[Anux]

Strange, shouldn't Bitmaps only influence random write performance? Like atime does?

I would be interested in the difference of mdadm with and without bitmaps or better internal/external bitmaps.

PS: here is an old article with 10k RPM HDDs: https://louwrentius.com/the-impact-o...rformance.html

[zexelon]

Now this is really interesting! LVM RAID is md under the hood, so would this significantly improve LVM RAID setups?

[Gamer1227]

I know it is sequential throughput, but those numbers are wild nonetheless!

He said tail latency reduced by 85%, wich is the main factor for random performace

[Raka555]

I always have to be that guy ...

I wonder if this still plays nice with hard disks, since many people use linux as a NAS for bulk storage on rotating media...

[Espionage724]

Oddly-specific optimization, but I'd totally be RAID0'ing 4 NVMes just to do it (I had an Acer Predator Skylake laptop that came with 2 256GB NVMe drives out-the-box RAID0 config'd through Intel RST that was pretty cool)

[ernsteiswuerfel]

I wonder if (and how much) RAID-performance with traditional harddisks has increased too? Still got my RAID5 array running with ye goode olde el cheapo rustbuckets. Didn't see any details about that on the LKML message.

[schmidtbag]

I doubt HDDs would be impacted. Perhaps 10Gbps SAS drives could be since they have larger caches and faster read/write speeds, but the thing about HDDs is they tend to be controlled by a single controller, whereas NVMe drives are directly connected to the PCIe bus and therefore are going to differ in their CPU overhead.
Having said that, I doubt that even SATA SSDs are really affected much by this.