Date: Sun, 26 Jul 2020 09:04:02 -0400 From: Aryeh Friedman <aryeh.friedman@gmail.com> To: "Steve O'Hara-Smith" <steve@sohara.org> Cc: FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: Ask stupid questions and you'll get a stupid answers, was: Technological advantages over Linux Message-ID: <CAGBxaX=iMog%2BLwg0vBCxCxsMwHKQ6i7-NbnQ-AGjUCXzs1eG-g@mail.gmail.com> In-Reply-To: <20200726134331.5c960f7f93d76d2249bd769c@sohara.org> References: <20200214204838.360c8f624397c659946bd764@sohara.org> <20200215063818.GE1482@admin.sibptus.ru> <20200215083359.367d8a3e9ddb4942df67d5b5@sohara.org> <58202623-bbf7-eda0-5cb5-fb4749e91e20@watters.ws> <CAEJNuHxbFSPBB7keSrBufpg=RsgQ8EPK_fvzt8XBROLNKyN_sw@mail.gmail.com> <6318251A-973A-4DEC-9271-12333EB11F7B@kicp.uchicago.edu> <CAEJNuHxC7i%2Bq7cq65=my6mJZDdiK4gpQsKjMU1nvsm=Ri4On%2Bg@mail.gmail.com> <ce61b5e9-b71c-e5b7-c64d-f79884c87435@watters.ws> <20200725152412.GJ92589@admin.sibptus.ru> <CAGBxaX=Ktr-pqtT8FU37ajkYonVLYT_WhSenn23Tj5b=i0d-8g@mail.gmail.com> <20200725162403.GA4721@admin.sibptus.ru> <CAGBxaXmBZcCWqAZFR9OSyRGrqGFU%2BqCAZ8CfOi=0oXAmf-2=tA@mail.gmail.com> <20200725182554.deffc63058a7c9f6d343ef06@sohara.org> <04df312d-9b2b-1873-2117-79a49e089bd9@kicp.uchicago.edu> <CAGBxaX=SR_sm7Pa5KXmTT=P6SCpvuyg9GhVa9WkxdPJM_HUBrg@mail.gmail.com> <20200726074655.b0036a0f90508156205376f9@sohara.org> <CAGBxaXn5-hQiC56v3u1T8_V339i1WDXu5iq9hq-WUaS%2BsrC_Zw@mail.gmail.com> <20200726134331.5c960f7f93d76d2249bd769c@sohara.org>
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On Sun, Jul 26, 2020 at 8:43 AM Steve O'Hara-Smith <steve@sohara.org> wrote: > > There is system wide performance loss due to pages having been > pushed out to swap and needing to be pulled in to be used. The more times > you push the memory over the edge like that the more random things get > pushed out to swap and the more random delays there will be as they get > pulled back in. This happens because some of the stuff that got pushed to > swap the first time round never comes back in (it isn't used often enough) > and so every time round more and more important stuff gets pushed out to > swap. > > Here is a variant of your experiment that should demonstrate it. > > 1: Reboot machine, measure performance > 2: Memory stress machine to until swapping reduces performance > 3: Kill memory stressing process > 4: Disable swap - which forces all pages back into RAM > 5: Enable swap > 6: Loop to 2 > Since stealing memory from a running process that counts on it to be functional will crash the process and odds are that process is something low level and critical to keeping X running the above variant is not practical to do and thus my current solution has the same effect -- reboot. But that being said there is nothing about firefox, libreoffice or just playing MP3's that should cause swapping on a machine with 24 GB of RAM! (Yes I run tomcat but that has only one small test webapp on it [debugging issues for a bigger one I support, the bigger one runs just fine on vm at a hosting company with 8 GB and 2 cores]) -- Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org
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