Added here - http://directory.fedora.redhat.com/wiki/Performance_Tuning#Database_Tuning_Considerations David Boreham wrote: > George Holbert wrote: > >> When tuning FDS on a Solaris machine, I've heard two different >> suggestions about nsslapd-dbcachesize: >> 1. Decrease nsslapd-dbcachesize, and instead rely on Solaris' >> built-in filesystem cache which performs better. >> 2. Tune nsslapd-dbcachesize up to a value that is at least as large >> as the size of your backend LDBM database. > > > The filesystem cache doesn't really perform better. (Pages that are > in the db cache are used directly from process memory. Any page > that is not resident in the db cache must be fetched from the filesystem, > incuring a user/kernel transition and a memory copy of the payload.) > Someone way back ran some tests and convinced themselves that it > did, and then wrote that doc ;) Actually there was some basis in reality > until recently we didn't have a 64-bit Solaris version, however the > filesystem cache was able to use 64-bit address space. So for VLDB > deployments it was true that the filesystem cache delivered better > overall use of system memory beyond 2-ishGbytes. > > But, the filesystem cache does ok (as is the case on all modern OS'es) > so if you aren't looking for tip-top performance it's fine to confiure a > smallish db cache and rely mostly on the filesystem. > > One thing to note is that the db cache is mmap'ed, and Solaris does > some very strange and evil things with mmap'ed files that are not > in tmpfs filesystems (it will decide all of a sudden to write back > dirty pages to disk at an amazing rate, to the exclusion of performing > all other useful work on the box). The solution to this problem is > documented : put the db home dir in tmpfs (or use sysv memory, > but that's not officially supported I don't think). > > > -- > Fedora-directory-users mailing list > Fedora-directory-users at redhat.com > https://www.redhat.com/mailman/listinfo/fedora-directory-users -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 3312 bytes Desc: S/MIME Cryptographic Signature Url : http://lists.fedoraproject.org/pipermail/389-users/attachments/20050909/a8839be2/attachment.bin
