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Sun, 26 Jul 2020 06:04:13 -0700 (PDT) MIME-Version: 1.0 References: <20200214204838.360c8f624397c659946bd764@sohara.org> <20200215063818.GE1482@admin.sibptus.ru> <20200215083359.367d8a3e9ddb4942df67d5b5@sohara.org> <58202623-bbf7-eda0-5cb5-fb4749e91e20@watters.ws> <6318251A-973A-4DEC-9271-12333EB11F7B@kicp.uchicago.edu> <20200725152412.GJ92589@admin.sibptus.ru> <20200725162403.GA4721@admin.sibptus.ru> <20200725182554.deffc63058a7c9f6d343ef06@sohara.org> <04df312d-9b2b-1873-2117-79a49e089bd9@kicp.uchicago.edu> <20200726074655.b0036a0f90508156205376f9@sohara.org> <20200726134331.5c960f7f93d76d2249bd769c@sohara.org> In-Reply-To: <20200726134331.5c960f7f93d76d2249bd769c@sohara.org> From: Aryeh Friedman Date: Sun, 26 Jul 2020 09:04:02 -0400 Message-ID: Subject: Re: Ask stupid questions and you'll get a stupid answers, was: Technological advantages over Linux To: "Steve O'Hara-Smith" Cc: FreeBSD Mailing List X-Rspamd-Queue-Id: 4BF36k3vRZz4Yf4 X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; 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RCVD_COUNT_TWO(0.00)[2]; ASN(0.00)[asn:15169, ipnet:2607:f8b0::/32, country:US]; TAGGED_FROM(0.00)[]; DWL_DNSWL_NONE(0.00)[gmail.com:dkim] Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.33 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 26 Jul 2020 13:04:15 -0000 On Sun, Jul 26, 2020 at 8:43 AM Steve O'Hara-Smith 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