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A comment on The logging framework isn't a bottleneck, and other lies your laptop tells you. Parent comment

Re:The logging framework isn't a bottleneck, and other lies ... by vbezhenar on Thursday May 14, 2020 @02:37AM (#23176149)
Sometimes that requires expertise in a very low-level topics. For example I've read a similar story, but developer digged the truth. Production was running on vmware cluster with live migration or something like that. Servers used slightly different CPUs (frequency differed a bit), so VMware emulated some important instruction (something related to get current timestamp). MSSQL used that instruction a lot in one specific scenario, so it was running much slower on virtualized production server.

They were able to figure it out and rewrote one stored procedure so it ran fast again. But I'm sure that I, for example, don't possess the necessary expertise to figure this out. I wouldn't be surprised that in many small-to-medium companies there are no experts of that level either.

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Re:The logging framework isn't a bottleneck, and other lies ... by xxs on Thursday May 14, 2020 @03:41AM (#23176608)
Time Stamp Counter (TSC) has been trapped to make sure it returns the same value across all cores. Intel fixed that part, though.
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Re:The logging framework isn't a bottleneck, and other lies ... by zorked on Thursday May 14, 2020 @04:17AM (#23176866)
In a live migration scenario the TSC in the source and destination machines will be necessarily different so that emulation is required to make it not warp.

That said, due to previous TSC instability all operating systems deal with a TSC warp pretty well. Whether applications deal well with it is probably the reason why emulation is the default, but it could be that this can be disabled.

(Everything AFAIRC)

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Re:The logging framework isn't a bottleneck, and other lies ... by vardump on Thursday May 14, 2020 @04:26AM (#23176934)
Sure, across all cores on a physical CPU socket. But not across CPU sockets.
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Re:The logging framework isn't a bottleneck, and other lies ... by RedShift1 on Thursday May 14, 2020 @07:25AM (#23178165)
Probably VMware fault tolerance which keeps a virtual machine in sync over 2 physical machines to allow instant failover. But I can imagine that taking a lot of instruction trapping.
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Re:The logging framework isn't a bottleneck, and other lies ... by gvjddbnvdrbv on Thursday May 14, 2020 @03:05AM (#23176343)
I would never get the CPU instruction bit but I'd like to think I'd get as far as the stored proceedure.
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