Presentation describing the logic behind adding dynamic memory allocation to
UFS dirhash
can be found at:
EuroBSDCon 2008 - Nick Barkas - Dynamic memory allocation for dirhash in
UFS2
http://www.za.freebsd.org/multimedia/tag-nick_barkas.html
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Observation relevant to tuning vfs.ufs.dirhash_maxmem:
When swap is in use
dirhash_mem hovers between 10% and 20% of dirhash_maxmem
due to frequent scavenging.
This indicates active dirhash_mem effectively behaves differently during low
memory,
and that the dirhash_reclaimage setting is
I have seen significant benefits from setting the UFS dirhash cache tuneables
to effective values,
and I believe all FreeBSD users will see at least a small benefit as well.
The ball for establishing production defaults appears to have been dropped
in 2008.
I am suggesting we pick it up and
Here is a more recent dialog between the developers.
quote
Nick Barkas
http://markmail.org/message/3sufphda2exjmhnq#query:+page:1+mid:3sufphda2exjmhnq+state:results
On Wed, May 27, 2009 at 12:36:49PM +0200, Nick Barkas wrote:
Some time during the next week or so, I plan on committing the
After scouring the internet,
it seems that no one else has done a great deal of testing of UFS2 dirhash
defaults lately.
As the dirhash feature has effectively been tested for regressions,
I would like to propose setting the default dirhash values to my original
recommendation:
Torfinn Ingolfsen-5 wrote
On Tue, 27 Aug 2013 23:58:10 -0400
Robert Burmeister lt;
Robert.Burmeister@
gt; wrote:
As 64 bit platforms tend to have more RAM and use ZFS,
Do you have any numbers for the 64 bit platforms tend to use ZFS?
PCBSD and OSX both default to ZFS for their 64 bit
I believe that increasing the following values by 10 would benefit
most FreeBSD users without disadvantage.
vfs.ufs.dirhash_maxmem: 2097152 to 20971520
vfs.ufs.dirhash_reclaimage: 5 to 50 or 60
vfs.ufs.dirhash_maxmem is further autotuned based on available
physical memory.
See r214359
Ivan Voras-7 wrote
On 28/08/2013 05:58, Robert Burmeister wrote:
On 8/27/2013 9:40 AM, Sergey Kandaurov wrote:
On 27 August 2013 16:41, Robert Burmeister
lt;
Robert.Burmeister@
gt; wrote:
I believe that increasing the following values by 10 would benefit
most FreeBSD users without
For previous benchmarks on the effect of the dirhash cache see:
https://wiki.freebsd.org/DirhashDynamicMemory
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Dewayne Geraghty-4 wrote
I'll bump vfs.ufs.dirhash_reclaimage to 60, it's worth it.
From the analysis perforned in 2009, and referenced earlier by Robert,
this
https://wiki.freebsd.org/DirhashDynamicMemory and other material at this
site,
indicates that the reclaimage interval is workload
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