In message <20201030233138.GD34923_at_zxy.spb.ru>, Slawa Olhovchenkov writes: > On Fri, Oct 30, 2020 at 04:00:55PM -0700, Cy Schubert wrote: > > > > > > More stresses memory usually refers to performance penalty. > > > > > Usually way for better performance is reduce memory access. > > > > > > > > The reason filesystems (UFS, ZFS, EXT4, etc.) cache is to avoid disk > > > > accesses. Nanoseconds vs milliseconds. > > > > > > I mean compared ZoL ZFS ARC vs old (BSD/Opensolaris/Illumos) ZFS ARC. > > > Any reaason to rise ARC hit rate in ZoL case? > > > > That's what hit rate is. It's a memory access instead of a disk access. > > That's what you want. > > Is ZoL ARC hit rate rise from FreeBSD ARC hit rate? We don't know that. You should be able to find out by running some tests that would populate your ARC and run the test again. I see that my -DNO_CLEAN buildworlds run faster, when I run them a second or third time after making a minor edit, than they did before. Thus I assume it uses memory more efficiently. By default it stores more metadata in ARC, 75% instead of IIRC 25% by default. Getting back to your original question. A more efficient ARC would exercise your memory more intensely because you are replacing disk reads with memory reads. And as I said before the old ZFS "found" weak RAM on three separate occasions in three different machines over the last ten years. You're advised to replace the marginal memory. -- Cheers, Cy Schubert <Cy.Schubert_at_cschubert.com> FreeBSD UNIX: <cy_at_FreeBSD.org> Web: https://FreeBSD.org NTP: <cy_at_nwtime.org> Web: https://nwtime.org The need of the many outweighs the greed of the few.Received on Fri Oct 30 2020 - 22:50:39 UTC
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