On Tue, Jan 9, 2018 at 6:24 AM, Catalin Iacob <iacobcata...@gmail.com> wrote: > On Fri, Dec 1, 2017 at 10:09 PM, Thomas Munro > <thomas.mu...@enterprisedb.com> wrote: >>> On 11/30/17 23:35, Thomas Munro wrote: >>>> Hmm. Yeah, it does, but apparently it's not so transparent. So if we >>>> mention that we'd better indicate in the same paragraph that you >>>> probably don't actually want to use it. How about the attached? > > Here's a review for v3.
Thanks! > I find that the first paragraph is an improvement as it's more precise. > > What I didn't like about the second paragraph is that it pointed out > Linux transparent huge pages too favorably while they are actually > known to cause big (huge?, pardon the pun) issues (as witnessed in > this thread as well). v3 basically says "in Linux it can be > transparent or explicit and explicit is faster than transparent". > Reading that, and seeing that explicit needs tweaking of kernel > parameters and so on, one might very well conclude "I'll use the > slightly-slower-but-still-better-than-nothing transparent version". > > So I tried to redo the second paragraph and ended up with the > attached. Rationale for the changes: > * changed "this feature" to "explicitly requesting huge pages" to > contrast with the automatic one described below > * made the wording of Linux THP more negative (but still with some > wiggle room for future kernel versions which might improve THP), > contrasting with the positive explicit request from this GUC > * integrated your mention of other OSes with automatic huge pages > * moved the new text to the last paragraph to lower its importance > > What do you think? I don't know enough about this to make such a strong recommendation myself, which is why I was only trying to report that bad performance had been observed on some version, not that you shouldn't do it. Any other views on this stronger statement? -- Thomas Munro http://www.enterprisedb.com