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Btrfs: Fix streaming read performance with checksumming on

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Large streaming reads make for large bios, which means each entry on the
list async work queues represents a large amount of data.  IO
congestion throttling on the device was kicking in before the async
worker threads decided a single thread was busy and needed some help.

The end result was that a streaming read would result in a single CPU
running at 100% instead of balancing the work off to other CPUs.

This patch also changes the pre-IO checksum lookup done by reads to
work on a per-bio basis instead of a per-page.  This results in many
extra btree lookups on large streaming reads.  Doing the checksum lookup
right before bio submit allows us to reuse searches while processing
adjacent offsets.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2008-07-31 15:42:53 -04:00
parent 37d1aeee39
commit 61b4944018
5 changed files with 99 additions and 54 deletions
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2
fs/btrfs/async-thread.c
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@ -160,7 +160,7 @@ void btrfs_init_workers(struct btrfs_workers *workers, int max)
INIT_LIST_HEAD(&workers->idle_list);
spin_lock_init(&workers->lock);
workers->max_workers = max;
workers->idle_thresh = 64;
workers->idle_thresh = 32;
}
/*