On Sun, 17 Mar 2019 13:54:04 +0100 "Carlos E. R." <robin.listas@telefonica.net> wrote:
On 17/03/2019 13.36, Dave Howorth wrote:
On Sun, 17 Mar 2019 13:23:35 +0100 "Carlos E. R." <> wrote:
On 17/03/2019 10.45, Per Jessen wrote:
David C. Rankin wrote:
On 03/16/2019 07:31 PM, Dave Howorth wrote:
So why are THP enabled by default? I could understand if they were set to madvise for example, but are they likely to make a huge difference on my 8 GB desktop?
And I don't understand why redis recommend a setting of never rather than madvise, if anybody has any thoughts on that?
I still don't understand why madvise doesn't solve all problems.
I don't even know what huge pages are about. Do you have some link for dummies out there? :-D
No, I just started googling a few hours before you :)
Wikipedia has nothing on THP.
Google points to
<https://docs.mongodb.com/manual/tutorial/transparent-huge-pages/>
«Transparent Huge Pages (THP) is a Linux memory management system that reduces the overhead of Translation Lookaside Buffer (TLB) lookups on machines with large amounts of memory by using larger memory pages.
However, database workloads often perform poorly with THP, because they tend to have sparse rather than contiguous memory access patterns. You should disable THP on Linux machines to ensure best performance with MongoDB.»
I don't think I understand much of that.
Is 8 GiB of RAM considered "large amount of memory"? So I'm wondering if I should disable it.
Dunno, I'm wondering too. That's why I'm asking questions.
Strange, they are disabled on 42.3.
On my Lenovo laptop with Leap42.3 and 8Gb memory, it is enabled.
cer@Telcontar:~> cat /sys/kernel/mm/transparent_hugepage/enabled [always] madvise never cer@Telcontar:~>
I suppose that is disabled. This machine has 8 GiB, a desktop with 15.0
No, that is enabled. The square brackets indicate the chosen option.
Ah, of course.
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