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* blkio: Implement dynamic io controlling policy registrationVivek Goyal2009-12-041-1/+13
| | | | | | | | | | | | | | | | | | | | o One of the goals of block IO controller is that it should be able to support mulitple io control policies, some of which be operational at higher level in storage hierarchy. o To begin with, we had one io controlling policy implemented by CFQ, and I hard coded the CFQ functions called by blkio. This created issues when CFQ is compiled as module. o This patch implements a basic dynamic io controlling policy registration functionality in blkio. This is similar to elevator functionality where ioschedulers register the functions dynamically. o Now in future, when more IO controlling policies are implemented, these can dynakically register with block IO controller. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Export some symbols from blkio as its user CFQ can be a moduleVivek Goyal2009-12-041-2/+2
| | | | | | | | | o blkio controller is inside the kernel and cfq makes use of interfaces exported by blkio. CFQ can be a module too, hence export symbols used by CFQ. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: make nonrot check logic consistentShaohua Li2009-12-041-1/+2
| | | | | | | | | | | cfq_arm_slice_timer() has logic to disable idle window for SSD device. The same thing should be done at cfq_select_queue() too, otherwise we will still see idle window. This makes the nonrot check logic consistent in cfq. Tests in a intel SSD with low_latency knob close, below patch can triple disk thoughput for muti-thread sequential read. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: move IO controller declerations to a header fileJens Axboe2009-12-041-0/+1
| | | | | | | They should not be declared inside some other file that's not related to CFQ. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Wait on sync-noidle queue even if rq_noidle = 1Vivek Goyal2009-12-031-1/+2
| | | | | | | | | | | | | | | | | o rq_noidle() is supposed to tell cfq that do not expect a request after this one, hence don't idle. But this does not seem to work very well. For example for direct random readers, rq_noidle = 1 but there is next request coming after this. Not idling, leads to a group not getting its share even if group_isolation=1. o The right solution for this issue is to scan the higher layers and set right flag (WRITE_SYNC or WRITE_ODIRECT). For the time being, this single line fix helps. This should not have any significant impact when we are not using cgroups. I will later figure out IO paths in higher layer and fix it. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Implement group_isolation tunableVivek Goyal2009-12-031-1/+36
| | | | | | | | | | | | | | | | | | | | | | | | | o If a group is running only a random reader, then it will not have enough traffic to keep disk busy and we will reduce overall throughput. This should result in better latencies for random reader though. If we don't idle on random reader service tree, then this random reader will experience large latencies if there are other groups present in system with sequential readers running in these. o One solution suggested by corrado is that by default keep the random readers or sync-noidle workload in root group so that during one dispatch round we idle only once on sync-noidle tree. This means that all the sync-idle workload queues will be in their respective group and we will see service differentiation in those but not on sync-noidle workload. o Provide a tunable group_isolation. If set, this will make sure that even sync-noidle queues go in their respective group and we wait on these. This provides stronger isolation between groups but at the expense of throughput if group does not have enough traffic to keep the disk busy. o By default group_isolation = 0 Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Determine async workload length based on total number of queuesVivek Goyal2009-12-031-5/+31
| | | | | | | | | | | | | | o Async queues are not per group. Instead these are system wide and maintained in root group. Hence their workload slice length should be calculated based on total number of queues in the system and not just queues in the root group. o As root group's default weight is 1000, make sure to charge async queue more in terms of vtime so that it does not get more time on disk because root group has higher weight. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Wait for cfq queue to get backlogged if group is emptyVivek Goyal2009-12-031-5/+29
| | | | | | | | | | | | | o If a queue consumes its slice and then gets deleted from service tree, its associated group will also get deleted from service tree if this was the only queue in the group. That will make group loose its share. o For the queues on which we have idling on and if these have used their slice, wait a bit for these queues to get backlogged again and then expire these queues so that group does not loose its share. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Propagate cgroup weight updation to cfq groupsVivek Goyal2009-12-031-0/+6
| | | | | | | o Propagate blkio cgroup weight updation to associated cfq groups. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Drop the reference to queue once the task changes cgroupVivek Goyal2009-12-031-0/+39
| | | | | | | | | o If a task changes cgroup, drop reference to the cfqq associated with io context and set cfqq pointer stored in ioc to NULL so that upon next request arrival we will allocate a new queue in new group. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Provide some isolation between groupsVivek Goyal2009-12-031-10/+20
| | | | | | | | | | | | | o Do not allow following three operations across groups for isolation. - selection of co-operating queues - preemtpions across groups - request merging across groups. o Async queues are currently global and not per group. Allow preemption of an async queue if a sync queue in other group gets backlogged. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Export disk time and sectors used by a group to user spaceVivek Goyal2009-12-031-3/+16
| | | | | | | | | | | o Export disk time and sector used by a group to user space through cgroup interface. o Also export a "dequeue" interface to cgroup which keeps track of how many a times a group was deleted from service tree. Helps in debugging. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Some debugging aids for CFQVivek Goyal2009-12-031-1/+18
| | | | | | | o Some debugging aids for CFQ. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Take care of cgroup deletion and cfq group reference countingVivek Goyal2009-12-031-0/+95
| | | | | | | | | | o One can choose to change elevator or delete a cgroup. Implement group reference counting so that both elevator exit and cgroup deletion can take place gracefully. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Nauman Rafique <nauman@google.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Dynamic cfq group creation based on cgroup tasks belongs toVivek Goyal2009-12-031-11/+100
| | | | | | | | | | | | o Determine the cgroup IO submitting task belongs to and create the cfq group if it does not exist already. o Also link cfqq and associated cfq group. o Currently all async IO is mapped to root group. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Group time used accounting and workload context save restoreVivek Goyal2009-12-031-0/+79
| | | | | | | | | | | | | | o This patch introduces the functionality to do the accounting of group time when a queue expires. This time used decides which is the group to go next. o Also introduce the functionlity to save and restore the workload type context with-in group. It might happen that once we expire the cfq queue and group, a different group will schedule in and we will lose the context of the workload type. Hence save and restore it upon queue expiry. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Implement per cfq group latency target and busy queue avgVivek Goyal2009-12-031-20/+45
| | | | | | | | | | | o So far we had 300ms soft target latency system wide. Now with the introduction of cfq groups, divide that latency by number of groups so that one can come up with group target latency which will be helpful in determining the workload slice with-in group and also the dynamic slice length of the cfq queue. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Introduce per cfq group weights and vdisktime calculationsVivek Goyal2009-12-031-1/+61
| | | | | | | | | o Bring in the per cfq group weight and how vdisktime is calculated for the group. Also bring in the functionality of updating the min_vdisktime of the group service tree. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Introduce the root service tree for cfq groupsVivek Goyal2009-12-031-3/+134
| | | | | | | | | o So far we just had one cfq_group in cfq_data. To create space for more than one cfq_group, we need to have a service tree of groups where all the groups can be queued if they have active cfq queues backlogged in these. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Keep queue on service tree until we expire itVivek Goyal2009-12-031-21/+49
| | | | | | | | | | | | | o Currently cfqq deletes a queue from service tree if it is empty (even if we might idle on the queue). This patch keeps the queue on service tree hence associated group remains on the service tree until we decide that we are not going to idle on the queue and expire it. o This just helps in time accounting for queue/group and in implementation of rest of the patches. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Implement macro to traverse each service tree in groupVivek Goyal2009-12-031-16/+25
| | | | | | | | | | | o Implement a macro to traverse each service tree in the group. This avoids usage of double for loop and special condition for idle tree 4 times. o Macro is little twisted because of special handling of idle class service tree. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Introduce the notion of cfq groupsVivek Goyal2009-12-031-33/+75
| | | | | | | | | | | | | | | | | | | | | | | | o This patch introduce the notion of cfq groups. Soon we will can have multiple groups of different weights in the system. o Various service trees (prioclass and workload type trees), will become per cfq group. So hierarchy looks as follows. cfq_groups | workload type | cfq queue o When an scheduling decision has to be taken, first we select the cfq group then workload with-in the group and then cfq queue with-in the workload type. o This patch just makes various workload service tree per cfq group and introduce the function to be able to choose a group for scheduling. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* blkio: Set must_dispatch only if we decided to not dispatch the requestVivek Goyal2009-12-031-3/+3
| | | | | | | | o must_dispatch flag should be set only if we decided not to run the queue and dispatch the request. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: no dispatch limit for single queueShaohua Li2009-12-031-2/+2
| | | | | | | | | | | | | | Since commit 2f5cb7381b737e24c8046fd4aeab571fb71315f5, each queue can send up to 4 * 4 requests if only one queue exists. I wonder why we have such limit. Device supports tag can send more requests. For example, AHCI can send 31 requests. Test (direct aio randread) shows the limits reduce about 4% disk thoughput. On the other hand, since we send one request one time, if other queue pop when current is sending more than cfq_quantum requests, current queue will stop send requests soon after one request, so sounds there is no big latency. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* Revert "cfq: Make use of service count to estimate the rb_key offset"Jens Axboe2009-11-301-6/+2
| | | | | | | | | | This reverts commit 3586e917f2c7df769d173c4ec99554cb40a911e5. Corrado Zoccolo <czoccolo@gmail.com> correctly points out, that we need consistency of rb_key offset across groups. This means we cannot properly use the per-service_tree service count. Revert this change. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: fix corner cases in idling logicCorrado Zoccolo2009-11-261-10/+22
| | | | | | | | | | | | | | | | | | Idling logic was disabled in some corner cases, leading to unfair share for noidle queues. * the idle timer was not armed if there were other requests in the driver. unfortunately, those requests could come from other workloads, or queues for which we don't enable idling. So we will check only pending requests from the active queue * rq_noidle check on no-idle queue could disable the end of tree idle if the last completed request was rq_noidle. Now, we will disable that idle only if all the queues served in the no-idle tree had rq_noidle requests. Reported-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: idling on deep seeky sync queuesCorrado Zoccolo2009-11-261-1/+12
| | | | | | | | | | | | | | | | Seeky sync queues with large depth can gain unfairly big share of disk time, at the expense of other seeky queues. This patch ensures that idling will be enabled for queues with I/O depth at least 4, and small think time. The decision to enable idling is sticky, until an idle window times out without seeing a new request. The reasoning behind the decision is that, if an application is using large I/O depth, it is already optimized to make full utilization of the hardware, and therefore we reserve a slice of exclusive use for it. Reported-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: fix no-idle preemption logicCorrado Zoccolo2009-11-261-2/+3
| | | | | | | | | | | | | | | | An incoming no-idle queue should preempt the active no-idle queue only if the active queue is idling due to service tree empty. Previous code was buggy in two ways: * it relied on service_tree field to be set on the active queue, while it is not set when the code is idling for a new request * it didn't check for the service tree empty condition, so could lead to LIFO behaviour if multiple queues with depth > 1 were preempting each other on an non-NCQ device. Reported-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: fix ncq detection codeCorrado Zoccolo2009-11-261-9/+15
| | | | | | | | | | | | | | | | | | | | | | CFQ's detection of queueing devices initially assumes a queuing device and detects if the queue depth reaches a certain threshold. However, it will reconsider this choice periodically. Unfortunately, if device is considered not queuing, CFQ will force a unit queue depth for some workloads, thus defeating the detection logic. This leads to poor performance on queuing hardware, since the idle window remains enabled. Given this premise, switching to hw_tag = 0 after we have proved at least once that the device is NCQ capable is not a good choice. The new detection code starts in an indeterminate state, in which CFQ behaves as if hw_tag = 1, and then, if for a long observation period we never saw large depth, we switch to hw_tag = 0, otherwise we stick to hw_tag = 1, without reconsidering it again. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: cleanup unreachable codeCorrado Zoccolo2009-11-261-13/+0
| | | | | | | | | | | | | | | cfq_should_idle returns false for no-idle queues that are not the last, so the control flow will never reach the removed code in a state that satisfies the if condition. The unreachable code was added to emulate previous cfq behaviour for non-NCQ rotational devices. My tests show that even without it, the performances and fairness are comparable with previous cfq, thanks to the fact that all seeky queues are grouped together, and that we idle at the end of the tree. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq: Make use of service count to estimate the rb_key offsetGui Jianfeng2009-11-261-2/+6
| | | | | | | | | | | For the moment, different workload cfq queues are put into different service trees. But CFQ still uses "busy_queues" to estimate rb_key offset when inserting a cfq queue into a service tree. I think this isn't appropriate, and it should make use of service tree count to do this estimation. This patch is for for-2.6.33 branch. Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* block: jiffies fixesRandy Dunlap2009-11-111-0/+1
| | | | | | | | | Use HZ-independent calculation of milliseconds. Add jiffies.h where it was missing since functions or macros from it are used. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: fix next_rq computationCorrado Zoccolo2009-11-081-6/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Cfq has a bug in computation of next_rq, that affects transition between multiple sequential request streams in a single queue (e.g.: two sequential buffered writers of the same priority), causing the alternation between the two streams for a transient period. 8,0 1 18737 0.260400660 5312 D W 141653311 + 256 8,0 1 20839 0.273239461 5400 D W 141653567 + 256 8,0 1 20841 0.276343885 5394 D W 142803919 + 256 8,0 1 20843 0.279490878 5394 D W 141668927 + 256 8,0 1 20845 0.292459993 5400 D W 142804175 + 256 8,0 1 20847 0.295537247 5400 D W 141668671 + 256 8,0 1 20849 0.298656337 5400 D W 142804431 + 256 8,0 1 20851 0.311481148 5394 D W 141668415 + 256 8,0 1 20853 0.314421305 5394 D W 142804687 + 256 8,0 1 20855 0.318960112 5400 D W 142804943 + 256 The fix makes sure that the next_rq is computed from the last dispatched request, and not affected by merging. 8,0 1 37776 4.305161306 0 D W 141738087 + 256 8,0 1 37778 4.308298091 0 D W 141738343 + 256 8,0 1 37780 4.312885190 0 D W 141738599 + 256 8,0 1 37782 4.315933291 0 D W 141738855 + 256 8,0 1 37784 4.319064459 0 D W 141739111 + 256 8,0 1 37786 4.331918431 5672 D W 142803007 + 256 8,0 1 37788 4.334930332 5672 D W 142803263 + 256 8,0 1 37790 4.337902723 5672 D W 142803519 + 256 8,0 1 37792 4.342359774 5672 D W 142803775 + 256 8,0 1 37794 4.345318286 0 D W 142804031 + 256 Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: get rid of the coop_preempt flagJens Axboe2009-11-041-19/+2
| | | | | | | We need to rework this logic post the cooperating cfq_queue merging, for now just get rid of it and Jeff Moyer will fix the fall out. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* cfq-iosched: fix merge errorJens Axboe2009-11-031-1/+0
| | | | | | | We ended up with testing the same condition twice, pretty pointless. Remove that first if. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* Merge branch 'for-linus' into for-2.6.33Jens Axboe2009-11-031-2/+20
|\ | | | | | | | | | | | | Conflicts: block/cfq-iosched.c Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| * cfq-iosched: limit coop preemptionShaohua Li2009-11-031-2/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | CFQ has an optimization for cooperated applications. if several io-context have close requests, they will get boost. But the optimization get abused. Considering thread a, b, which work on one file. a reads sectors s, s+2, s+4, ...; b reads sectors s+1, s+3, s +5, ... Both a and b are sequential read, so they can open idle window. a reads a sector s and goes to idle window and wakeup b. b reads sector s+1, since in current implementation, cfq_should_preempt() thinks a and b are cooperators, b will preempt a. b then reads sector s+1 and goes to idle window and wakeup a. for the same reason, a will preempt b and reads s+2. a and b will continue the circle. The circle will be very long, and a and b will occupy whole disk queue. Other applications will nearly have no chance to run. Fix this limiting coop preempt until a queue is scheduled normally again. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Acked-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| * cfq-iosched: fix bad return value cfq_should_preempt()Jens Axboe2009-11-031-1/+1
| | | | | | | | | | | | | | | | Commit a6151c3a5c8e1ff5a28450bc8d6a99a2a0add0a7 inadvertently reversed a preempt condition check, potentially causing a performance regression. Make the meta check correct again. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* | Merge branch 'cfq-2.6.33' into for-2.6.33Jens Axboe2009-11-031-52/+321
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| * | cfq-iosched: fix style issue in cfq_get_avg_queues()Jens Axboe2009-10-281-2/+2
| | | | | | | | | | | | | | | | | | Line breaks and bad brace placement. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| * | cfq-iosched: fairness for sync no-idle queuesCorrado Zoccolo2009-10-281-32/+168
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently no-idle queues in cfq are not serviced fairly: even if they can only dispatch a small number of requests at a time, they have to compete with idling queues to be serviced, experiencing large latencies. We should notice, instead, that no-idle queues are the ones that would benefit most from having low latency, in fact they are any of: * processes with large think times (e.g. interactive ones like file managers) * seeky (e.g. programs faulting in their code at startup) * or marked as no-idle from upper levels, to improve latencies of those requests. This patch improves the fairness and latency for those queues, by: * separating sync idle, sync no-idle and async queues in separate service_trees, for each priority * service all no-idle queues together * and idling when the last no-idle queue has been serviced, to anticipate for more no-idle work * the timeslices allotted for idle and no-idle service_trees are computed proportionally to the number of processes in each set. Servicing all no-idle queues together should have a performance boost for NCQ-capable drives, without compromising fairness. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| * | cfq-iosched: enable idling for last queue on priority classCorrado Zoccolo2009-10-281-3/+31
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cfq can disable idling for queues in various circumstances. When workloads of different priorities are competing, if the higher priority queue has idling disabled, lower priority queues may steal its disk share. For example, in a scenario with an RT process performing seeky reads vs a BE process performing sequential reads, on an NCQ enabled hardware, with low_latency unset, the RT process will dispatch only the few pending requests every full slice of service for the BE process. The patch solves this issue by always performing idle on the last queue at a given priority class > idle. If the same process, or one that can pre-empt it (so at the same priority or higher), submits a new request within the idle window, the lower priority queue won't dispatch, saving the disk bandwidth for higher priority ones. Note: this doesn't touch the non_rotational + NCQ case (no hardware to test if this is a benefit in that case). Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| * | cfq-iosched: reimplement priorities using different service treesCorrado Zoccolo2009-10-281-34/+82
| | | | | | | | | | | | | | | | | | | | | | | | | | | We use different service trees for different priority classes. This allows a simplification in the service tree insertion code, that no longer has to consider priority while walking the tree. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| * | cfq-iosched: preparation to handle multiple service treesCorrado Zoccolo2009-10-281-11/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We embed a pointer to the service tree in each queue, to handle multiple service trees easily. Service trees are enriched with a counter. cfq_add_rq_rb is invoked after putting the rq in the fifo, to ensure that all fields in rq are properly initialized. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| * | cfq-iosched: adapt slice to number of processes doing I/OCorrado Zoccolo2009-10-281-2/+51
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the number of processes performing I/O concurrently increases, a fixed time slice per process will cause large latencies. This patch, if low_latency mode is enabled, will scale the time slice assigned to each process according to a 300ms target latency. In order to keep fairness among processes: * The number of active processes is computed using a special form of running average, that quickly follows sudden increases (to keep latency low), and decrease slowly (to have fairness in spite of rapid decreases of this value). To safeguard sequential bandwidth, we impose a minimum time slice (computed using 2*cfq_slice_idle as base, adjusted according to priority and async-ness). Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* | | cfq-iosched: simplify prio-unboost codeCorrado Zoccolo2009-11-021-5/+3
|/ / | | | | | | | | | | | | Eliminate redundant checks. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* | cfq-iosched: improve hw_tag detectionShaohua Li2009-10-271-0/+12
| | | | | | | | | | | | | | | | | | | | If active queue hasn't enough requests and idle window opens, cfq will not dispatch sufficient requests to hardware. In such situation, current code will zero hw_tag. But this is because cfq doesn't dispatch enough requests instead of hardware queue doesn't work. Don't zero hw_tag in such case. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* | cfq: break apart merged cfqqs if they stop cooperatingJeff Moyer2009-10-261-3/+76
| | | | | | | | | | | | | | | | | | cfq_queues are merged if they are issuing requests within the mean seek distance of one another. This patch detects when the coopearting stops and breaks the queues back up. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* | cfq: change the meaning of the cfqq_coop flagJeff Moyer2009-10-261-14/+6
| | | | | | | | | | | | | | | | | | | | | | | | The flag used to indicate that a cfqq was allowed to jump ahead in the scheduling order due to submitting a request close to the queue that just executed. Since closely cooperating queues are now merged, the flag holds little meaning. Change it to indicate that multiple queues were merged. This will later be used to allow the breaking up of merged queues when they are no longer cooperating. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* | cfq: merge cooperating cfq_queuesJeff Moyer2009-10-261-2/+87
| | | | | | | | | | | | | | | | | | | | | | | | When cooperating cfq_queues are detected currently, they are allowed to skip ahead in the scheduling order. It is much more efficient to automatically share the cfq_queue data structure between cooperating processes. Performance of the read-test2 benchmark (which is written to emulate the dump(8) utility) went from 12MB/s to 90MB/s on my SATA disk. NFS servers with multiple nfsd threads also saw performance increases. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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