diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/block/biodoc.txt | 5 | ||||
| -rw-r--r-- | Documentation/cgroups/blkio-controller.txt | 30 | ||||
| -rw-r--r-- | Documentation/iostats.txt | 17 |
3 files changed, 9 insertions, 43 deletions
diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt index b9a83dd24732..2a7b38c832c7 100644 --- a/Documentation/block/biodoc.txt +++ b/Documentation/block/biodoc.txt @@ -963,11 +963,6 @@ elevator_dispatch_fn* fills the dispatch queue with ready requests. elevator_add_req_fn* called to add a new request into the scheduler -elevator_queue_empty_fn returns true if the merge queue is empty. - Drivers shouldn't use this, but rather check - if elv_next_request is NULL (without losing the - request if one exists!) - elevator_former_req_fn elevator_latter_req_fn These return the request before or after the one specified in disk sort order. Used by the diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt index 4ed7b5ceeed2..465351d4cf85 100644 --- a/Documentation/cgroups/blkio-controller.txt +++ b/Documentation/cgroups/blkio-controller.txt @@ -140,7 +140,7 @@ Proportional weight policy files - Specifies per cgroup weight. This is default weight of the group on all the devices until and unless overridden by per device rule. (See blkio.weight_device). - Currently allowed range of weights is from 100 to 1000. + Currently allowed range of weights is from 10 to 1000. - blkio.weight_device - One can specify per cgroup per device rules using this interface. @@ -343,34 +343,6 @@ Common files among various policies CFQ sysfs tunable ================= -/sys/block/<disk>/queue/iosched/group_isolation ------------------------------------------------ - -If group_isolation=1, it provides stronger isolation between groups at the -expense of throughput. By default group_isolation is 0. In general that -means that if group_isolation=0, expect fairness for sequential workload -only. Set group_isolation=1 to see fairness for random IO workload also. - -Generally CFQ will put random seeky workload in sync-noidle category. CFQ -will disable idling on these queues and it does a collective idling on group -of such queues. Generally these are slow moving queues and if there is a -sync-noidle service tree in each group, that group gets exclusive access to -disk for certain period. That means it will bring the throughput down if -group does not have enough IO to drive deeper queue depths and utilize disk -capacity to the fullest in the slice allocated to it. But the flip side is -that even a random reader should get better latencies and overall throughput -if there are lots of sequential readers/sync-idle workload running in the -system. - -If group_isolation=0, then CFQ automatically moves all the random seeky queues -in the root group. That means there will be no service differentiation for -that kind of workload. This leads to better throughput as we do collective -idling on root sync-noidle tree. - -By default one should run with group_isolation=0. If that is not sufficient -and one wants stronger isolation between groups, then set group_isolation=1 -but this will come at cost of reduced throughput. - /sys/block/<disk>/queue/iosched/slice_idle ------------------------------------------ On a faster hardware CFQ can be slow, especially with sequential workload. diff --git a/Documentation/iostats.txt b/Documentation/iostats.txt index f6dece5b7014..c76c21d87e85 100644 --- a/Documentation/iostats.txt +++ b/Documentation/iostats.txt @@ -1,8 +1,6 @@ I/O statistics fields --------------- -Last modified Sep 30, 2003 - Since 2.4.20 (and some versions before, with patches), and 2.5.45, more extensive disk statistics have been introduced to help measure disk activity. Tools such as sar and iostat typically interpret these and do @@ -46,11 +44,12 @@ the above example, the first field of statistics would be 446216. By contrast, in 2.6 if you look at /sys/block/hda/stat, you'll find just the eleven fields, beginning with 446216. If you look at /proc/diskstats, the eleven fields will be preceded by the major and -minor device numbers, and device name. Each of these formats provide +minor device numbers, and device name. Each of these formats provides eleven fields of statistics, each meaning exactly the same things. All fields except field 9 are cumulative since boot. Field 9 should -go to zero as I/Os complete; all others only increase. Yes, these are -32 bit unsigned numbers, and on a very busy or long-lived system they +go to zero as I/Os complete; all others only increase (unless they +overflow and wrap). Yes, these are (32-bit or 64-bit) unsigned long +(native word size) numbers, and on a very busy or long-lived system they may wrap. Applications should be prepared to deal with that; unless your observations are measured in large numbers of minutes or hours, they should not wrap twice before you notice them. @@ -96,11 +95,11 @@ introduced when changes collide, so (for instance) adding up all the read I/Os issued per partition should equal those made to the disks ... but due to the lack of locking it may only be very close. -In 2.6, there are counters for each cpu, which made the lack of locking -almost a non-issue. When the statistics are read, the per-cpu counters -are summed (possibly overflowing the unsigned 32-bit variable they are +In 2.6, there are counters for each CPU, which make the lack of locking +almost a non-issue. When the statistics are read, the per-CPU counters +are summed (possibly overflowing the unsigned long variable they are summed to) and the result given to the user. There is no convenient -user interface for accessing the per-cpu counters themselves. +user interface for accessing the per-CPU counters themselves. Disks vs Partitions ------------------- |
