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charset="ISO-8859-1" X-Mailer: Evolution 3.18.5.1 FreeBSD GNOME Team Port Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 298016A608 X-Spamd-Result: default: False [-0.24 / 15.00]; local_wl_from(0.00)[freebsd.org]; NEURAL_HAM_SHORT(-0.17)[-0.166,0]; ASN(0.00)[asn:16509, ipnet:52.28.0.0/16, country:US]; NEURAL_HAM_MEDIUM(-0.00)[-0.001,0]; NEURAL_HAM_LONG(-0.07)[-0.074,0] X-Rspamd-Server: mx1.freebsd.org X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 03 Dec 2018 19:34:08 -0000 On Tue, 2018-12-04 at 05:56 +1100, Bruce Evans wrote: > On Mon, 3 Dec 2018, Justin Hibbits wrote: > > [...] > > Please look at removing VM_KMEM_SIZE_SCALE completely.  I'm now trying to > convince kib that it is bogus for all arches, but only know exactly what > happens on x86. > > On arches with large kva, the scale factor should be 1 or smaller since > there is enough kva to map physmem several times. > > On arches with small kva, the kmem size should be as large as possible > and not depend on the physmem size (except as a micro-optimization for > space), since large physmem needs maximal kva and small physmem doesn't > require restricting kva. > > The scale factor of 3 just breaks booting FreeBSD-11 i386 with 48MB > physmem, by making kmem about 3 times smaller than it needs to be to > map this whole 48MB.  The nmbclusters allocation runs out first on my > test system, despite more overcommit for mbuf allocations than most. > > Bruce > I know we had problems with the default scaling on armv7 at $work when we tried to embed a large (150mb) mdrootfs into our kernel for a system with 2gb ram. I had to chase down the meaning of the scale variable (and I certainly could have misunderstood it to any degree), but here's what I wrote about it after fiddling and finding a value that worked for us. This was for early incarnations of 11-stable. # Tuning required to make the kernel work with a large # embedded filesystem... #  # Allocate one page of kmem_arena KVA for every # VM_KMEM_SIZE_SCALE pages of ram.  The default scale is 3, # and with a huge (>100MB) embedded mdroot that doesn't leave # enough virtual address space to allocate enough kernel # stacks, mbufs, and other resources that come out of KVA. options  VM_KMEM_SIZE_SCALE=5 -- Ian