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Re: openldap.git branch mdb.master updated. 3630066843b7ca6b2cd12911d3e2fe3314cd4549
Hallvard Breien Furuseth wrote:
On 27/07/14 03:27, openldap-commit2devel@OpenLDAP.org wrote:
Author: Howard Chu <firstname.lastname@example.org>
Date: Sat Jul 26 18:16:02 2014 -0700
Fix MIPS cache coherency on Linux
MIPS chips require manual control of on-chip caches. The cacheflush
syscall being used here only exists on MIPS Linux, other OSs will
I may be guessing wrong what's going on here, but anyway:
CACHEFLUSH looks like it belongs before setting me_txns->mti_txnid
which tells other threads/processes to use the new metapage.
If so, MDB_NOLOCK may be in trouble since it uses pick_meta()
instead of mti_txnid. Should there be a separate CACHEFLUSH after
writing the datapages if MDB_NOLOCK, and the current CACHEFLUSH
should just flush the metapages?
I don't see any reason for that. As always, the only thing that matters is
when the metapages get written.
Does the code contradict this comment above, or is it about
/* Memory ordering issues are irrelevant ... */
Quite simply, on MIPS, write()s into the buffer cache aren't coherent with the
on-chip data (or instruction, but irrelevant) cache.
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/