kerneltrap.org.
When I get some hard figures
on their performance, I'll put them up here.
The copyright on these patches is held by
Network Storage Solutions, Inc,
who are now
in
Chapter 11 bankruptcy proceedings
[though that link is dead].
They've released them under a BSD license,
see the subr_cluster.c file.
The notice should look real familiar.
I've updated the patches to apply against NetBSD-current as of early February 2004. There's only one patch file in this set.
The following striken out info is on the mechanics of applying the older patches from 2002.
There's 2 parts. There would be just one part
if I had known how to get cvs diff to work
like diff -N, but at the time
I made the patch, I didn't.
(Some kind soul has since
told me how that's done.
)
They apply to NetBSD-current as of 4 Sep 2002.
First,
there's
a patch to download and apply:
clust-diff.
The diff was taken from the sys/ directory
so run patch from there, something like:
csh% cd /usr/src/sys csh% patch < cluster-diffThis diff has been hand-edited to remove some stuff that isn't relevant. If the diff is cocked up, let me know.
Second, there's
a new kernel source file to add:
subr_cluster.c.
Install it like:
csh% cp subr_cluster.c /usr/src/sys/kern
I think the
subr_cluster.c
code might better belong in
subr_disk.c,
with its prototypes in
<sys/disk.h>.
However, the
hysterical porpoises are happy where it is for now, in its own
file with prototypes in
<sys/buf.h>.
Some kernel options of interest:
SD_CLUSTER |
Enables clustering by the sd driver.
I've tested this and it works |
WD_CLUSTER |
Enables clustering by the wd driver.
I haven't tested this, yet, but the code looks
an awful lot like the sd, so I'm
betting it works. Of course, I haven't compiled it,
yet.
|
MAX_CLUSTERS |
Default number of buffers allowed to be clustered together; defaults to the number of pages that fit in MAXPHYS (16 on an i386) on the assumption that you ordinarily transfer at least a page of data at a time |
MAX_CLUSTEREDVA |
Default amount of virtual memory mapped by clusters; defaults to 32M |
CLUSTER_STATS |
Enable this flag if you want the stats listed in the next table
enabled for non-DIAGNOSTIC kernels
|
MAX_CLUSTEREDVA should probably be
scaled to some percentage of total VA.
Some globals of interest:
dosdcluster |
Boolean controlling whether clusters are built
by the |
dowdcluster |
Ditto for the |
max_clusters |
Maximum number of buffers that can be clustered together
into a single disk xfer;
defaults to MAX_CLUSTERS, above
|
max_clusteredva |
Total amount of virtual address space mapped by clusters;
defaults to MAX_CLUSTEREDVA, above
|
totalclusters |
Counts the number of clusters built by the disk driver |
currentclusters |
The current number of clusters in transit to/from the disk |
missedclusters |
A count of the number of clusters that could have been built, but weren't because of a resource shortage like not enough RAM |
DIAGNOSTIC kernels
or those compiled with the CLUSTER_STATS option.
Ideally, all would be sysctl'ed and per-disk.
And mebbe a global max on the VA used by clusters
would be good, too.