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author | scottl <scottl@FreeBSD.org> | 2001-08-05 07:26:31 +0000 |
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committer | scottl <scottl@FreeBSD.org> | 2001-08-05 07:26:31 +0000 |
commit | 1f57f122959daa995b130f2ba0b9056fdd5e5a91 (patch) | |
tree | 756fd851980d0f4ace15ed87994ea04d49781cd5 /share/man | |
parent | 101574484ae8075461f71a6171097761a0c0042d (diff) | |
download | FreeBSD-src-1f57f122959daa995b130f2ba0b9056fdd5e5a91.zip FreeBSD-src-1f57f122959daa995b130f2ba0b9056fdd5e5a91.tar.gz |
Once again throw out the calculation of si_iosize_max and set it to 64K.
Although it can go higher, it is not safe to so do on arrays with many
members. Compromise by adding a tunable, "hw.aac.iosize_max" that can be
set at boottime. Also document in the aac(4) manpage.
MFC after: 4 weeks
Diffstat (limited to 'share/man')
-rw-r--r-- | share/man/man4/aac.4 | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/share/man/man4/aac.4 b/share/man/man4/aac.4 index 3988c4d..22167b9 100644 --- a/share/man/man4/aac.4 +++ b/share/man/man4/aac.4 @@ -100,6 +100,18 @@ disk/container interface .It Pa /boot/kernel/aac.ko aac loadable module .El +.Sh TUNING +The read-only sysctl +.Va hw.aac.iosize_max +defautls to 65536 and may be set at boot time to another value via +.Xr loader 8 . +This value determines the maximum data transfer size allowed +to/from an array. Setting it higher will result in better performance, +especially for large sequential access patterns. BEWARE: internal limitations +of the card limit this value to 64K for arrays with many members. While it +may be safe to raise this value, do so AT YOUR OWN RISK. Note also that +performance peaks at a value of 96K, and drops off dramatically at 128K, due +to other limitations of the card. .Sh DIAGNOSTICS Compiling with .Dv AAC_DEBUG |