From owner-freebsd-hackers@freebsd.org Wed Feb 24 18:36:17 2021 Return-Path: Delivered-To: freebsd-hackers@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id BC4E15657E8 for ; Wed, 24 Feb 2021 18:36:17 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4Dm4PX3VLRz4Rxw; Wed, 24 Feb 2021 18:36:16 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.16.1/8.16.1) with ESMTPS id 11OIa70A036073 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 24 Feb 2021 20:36:10 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua 11OIa70A036073 Received: (from kostik@localhost) by tom.home (8.16.1/8.16.1/Submit) id 11OIa7Js036072; Wed, 24 Feb 2021 20:36:07 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 24 Feb 2021 20:36:07 +0200 From: Konstantin Belousov To: Alan Somers Cc: Olivier Certner , FreeBSD Hackers Subject: Re: The out-of-swap killer makes poor choices Message-ID: References: <1984125.0OzZcVfBr4@ravel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on tom.home X-Rspamd-Queue-Id: 4Dm4PX3VLRz4Rxw X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=gmail.com (policy=none); spf=softfail (mx1.freebsd.org: 2001:470:d5e7:1::1 is neither permitted nor denied by domain of kostikbel@gmail.com) smtp.mailfrom=kostikbel@gmail.com X-Spamd-Result: default: False [-3.00 / 15.00]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; FREEMAIL_CC(0.00)[free.fr,freebsd.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.998]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; FREEMAIL_FROM(0.00)[gmail.com]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; HAS_XAW(0.00)[]; RBL_DBL_DONT_QUERY_IPS(0.00)[2001:470:d5e7:1::1:from]; R_SPF_SOFTFAIL(0.00)[~all]; SPAMHAUS_ZRD(0.00)[2001:470:d5e7:1::1:from:127.0.2.255]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_ALL(0.00)[]; NEURAL_HAM_SHORT(-1.00)[-1.000]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; RCVD_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+]; MAILMAN_DEST(0.00)[freebsd-hackers]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Technical discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Feb 2021 18:36:17 -0000 On Wed, Feb 24, 2021 at 10:34:23AM -0700, Alan Somers wrote: > There's another silly problem that I didn't mention in my original post. > The old rule of thumb is that the swap partition's size should be twice as > large as the amount of RAM. However, that's no longer possible in many > cases. The kernel imposes a hard limit of 64 GiB (on amd64 at least) on > the usable size of any swap partition, and many servers now have far more > than 64 GiB of RAM. So the advice needs to change with the times. I don't I do not think so. The usable size of the swap is determined by the amount of swap metadata we pre-configure at boot time. Usually it is sized proportionally to the available physical memory, but you can override swap zones size manually with the knob. > know what the best size would be for a modern server, but I would guess > that it must be at least several times the RSS of your largest process, and > also at least one tenth of RAM (for use as a dump device with compressed > core dumps). > -Alan