diff options
author | Ingo Molnar <mingo@elte.hu> | 2008-10-12 15:05:39 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-10-12 15:05:39 +0200 |
commit | a9b9e81c915e4a57ac3b21d1a7fa7ff184639780 (patch) | |
tree | 98304395fbb5b9c74fca35b196cd414c1949f280 /Documentation/block | |
parent | a8b71a2810386a5ac8f43d2095fe3355f0d8db37 (diff) | |
parent | fd048088306656824958e7783ffcee27e241b361 (diff) |
Merge branch 'linus' into x86/memory-corruption-check
Diffstat (limited to 'Documentation/block')
-rw-r--r-- | Documentation/block/deadline-iosched.txt | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/Documentation/block/deadline-iosched.txt b/Documentation/block/deadline-iosched.txt index c23cab13c3d..72576769e0f 100644 --- a/Documentation/block/deadline-iosched.txt +++ b/Documentation/block/deadline-iosched.txt @@ -30,12 +30,18 @@ write_expire (in ms) Similar to read_expire mentioned above, but for writes. -fifo_batch +fifo_batch (number of requests) ---------- -When a read request expires its deadline, we must move some requests from -the sorted io scheduler list to the block device dispatch queue. fifo_batch -controls how many requests we move. +Requests are grouped into ``batches'' of a particular data direction (read or +write) which are serviced in increasing sector order. To limit extra seeking, +deadline expiries are only checked between batches. fifo_batch controls the +maximum number of requests per batch. + +This parameter tunes the balance between per-request latency and aggregate +throughput. When low latency is the primary concern, smaller is better (where +a value of 1 yields first-come first-served behaviour). Increasing fifo_batch +generally improves throughput, at the cost of latency variation. writes_starved (number of dispatches) |