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cfq: improve fsync performance for small files

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Fsync performance for small files achieved by cfq on high-end disks is
lower than what deadline can achieve, due to idling introduced between
the sync write happening in process context and the journal commit.

Moreover, when competing with a sequential reader, a process writing
small files and fsync-ing them is starved.

This patch fixes the two problems by:
- marking journal commits as WRITE_SYNC, so that they get the REQ_NOIDLE
  flag set,
- force all queues that have REQ_NOIDLE requests to be put in the noidle
  tree.

Having the queue associated to the fsync-ing process and the one associated
 to journal commits in the noidle tree allows:
- switching between them without idling,
- fairness vs. competing idling queues, since they will be serviced only
  after the noidle tree expires its slice.

Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Tested-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Corrado Zoccolo
2010-09-20 15:24:50 +02:00
committed by Jens Axboe
parent 6d0aed7a38
commit 749ef9f842
3 changed files with 6 additions and 16 deletions
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2
fs/jbd/commit.c
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@@ -318,7 +318,7 @@ void journal_commit_transaction(journal_t *journal)
int first_tag = 0;
int tag_flag;
int i;
int write_op = WRITE;
int write_op = WRITE_SYNC;
/*
* First job: lock down the current transaction and wait for