[OpenIndiana-discuss] zsf send/receive performance

[Willem R. van den Berge]

That is an interesting thought. I did check the aggregate CPU utilization (Dual 6-core 2.0GHz Xeon, E5-2630L) and overall it looks fine with a load average below 0.5 during transfers. However,  I have not checked if there is a single thread that is blocking the process. I guess the cheap way to verify your assumption is to run the process on a faster processor. If the throughput goes up with the speed of the CPU that would indicate we're on the right track. I think we have a couple of E-2637v2's laying around, let me see if I can get those swapped in.

W






Willem R. van den Berge
Chief Technology Officer
WVandenberge at altep.com

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-----Original Message-----
From: Jim Klimov [mailto:jimklimov at cos.ru]
Sent: Monday, December 09, 2013 1:15 PM
To: openindiana-discuss at openindiana.org
Subject: Re: [OpenIndiana-discuss] zsf send/receive performance

Reading your description, I thought "can it be a single-CPU performance issue?" Perhaps, decompressing your datasets (or compressing upon write - though the /dev/null experiment rules that out), or building the stream, or any other step in your data path, might for some reason be a single-threaded task. Running several in parallel splits them across many cores, but one is slow.

Not being a ZFS developer, I am not ready to check and point the place in code where that guess might be (dis-)proved, but at least I'd start digging (and asking) with such an assumption :)

At least, there are many things in parallel IT processing that are made fast by sheer scale of concurrent independent tasks, rather than (expensively) trying to parallelize the code inside. And on average the cheap approach pays off ;)

//Jim


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