git: kernel - Improve cluster_read()
commit 6b84c93eb3b1e5815f00edf82f94fa12b79a9cc1
Author: Matthew Dillon <dillon@apollo.backplane.com>
Date: Mon Feb 8 09:51:05 2010 -0800
kernel - Improve cluster_read()
* The cluster_read() code was tripping over itself due to a findblk()
call which caused it to believe it had found a buffer hole when it
really found a busy buffer.
Redo the code to use the FINDBLK_TEST flag to locate the next buffer
hole. Also add a shortcut to support efficient coding for larger
read-ahead values.
* Change the single-read-ahead in cluster_read() to a multiple-read-ahead
based on the maxra parameter. Before we just did a single read-ahead
and even though this was a cluster read it still created a situation
where the next cluster_read(0 operation would stall on previous read-ahead
before issuing the next one. In otherwords, it wasn't pipelining requests
as well asit could.
This change tries to keep at least two read-aheads in progress so when
the next cluster_read() stalls on the first one the second one is still
in the pipeline after it unstalls, allowing it to issue the third one
to keep the pipeline hot.
* These changes improve SSD swapcache operation as well as normal HD
cluster_read() pipelining. In addition the read-ahead is now sufficient
to keep the pipeline hot across a 2 x Swap (interleaved) setup.
Summary of changes:
sys/kern/vfs_cluster.c | 88 ++++++++++++++++++++++++++++++------------------
1 files changed, 55 insertions(+), 33 deletions(-)
http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/6b84c93eb3b1e5815f00edf82f94fa12b79a9cc1
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