diff options
| author | Len Brown <len.brown@intel.com> | 2008-10-22 23:57:26 -0400 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2008-10-23 00:11:07 -0400 |
| commit | 057316cc6a5b521b332a1d7ccc871cd60c904c74 (patch) | |
| tree | 4333e608da237c73ff69b10878025cca96dcb4c8 /Documentation/block/deadline-iosched.txt | |
| parent | 3e2dab9a1c2deb03c311eb3f83466009147ed4d3 (diff) | |
| parent | 2515ddc6db8eb49a79f0fe5e67ff09ac7c81eab4 (diff) | |
Merge branch 'linus' into test
Conflicts:
MAINTAINERS
arch/x86/kernel/acpi/boot.c
arch/x86/kernel/acpi/sleep.c
drivers/acpi/Kconfig
drivers/pnp/Makefile
drivers/pnp/quirks.c
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/block/deadline-iosched.txt')
| -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) |