Alexander, On Fri, 3 Apr 2015, Alexander Motin wrote:
> Author: mav > Date: Fri Apr 3 14:45:48 2015 > New Revision: 281026 > URL: https://svnweb.freebsd.org/changeset/base/281026 > > Log: > Make ZFS ARC track both KVA usage and fragmentation. > > Even on Illumos, with its much larger KVA, ZFS ARC steps back if KVA usage > reaches certain threshold (3/4 on i386 or 16/17 otherwise). FreeBSD has > even less KVA, but had no such limit on archs with direct map as amd64. > As result, on machines with a lot of RAM, during load with very small user- > space memory pressure, such as `zfs send`, it was possible to reach state, > when there is enough both physical RAM and KVA (I've seen up to 25-30%), > but no continuous KVA range to allocate even single 128KB I/O request. > > Address this situation from two sides: > - restore KVA usage limitations in a way the most close to Illumos; > - introduce new requirement for KVA fragmentation, specifying that we > should have at least one sequential KVA range of zfs_max_recordsize bytes. > > Experiments show that first limitation done alone is not sufficient. On > machine with 64GB of RAM it is sometimes needed to drop up to half of ARC > size to get at leats one 1MB KVA chunk. Statically limiting ARC to half > of KVA/RAM is too strict, so second limitation makes it to work in cycles: > accumulate trash up to certain critical mass, do massive spring-cleaning, > and then start littering again. :) > > MFC after: 1 month Wow. Excellent dig, thank you. -- Sincerely, D.Marck [DM5020, MCK-RIPE, DM3-RIPN] [ FreeBSD committer: ma...@freebsd.org ] ------------------------------------------------------------------------ *** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- ma...@rinet.ru *** ------------------------------------------------------------------------ _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
