/*++

Copyright (c) 2008-2010 Alexandr A. Telyatnikov (Alter)

Module Name:
    id_probe.cpp

Abstract:
    This module handles comamnd queue reordering and channel load balance

Author:
    Alexander A. Telyatnikov (Alter)

Environment:
    kernel mode only

Notes:

    THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
    IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
    IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
    NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Revision History:

--*/

#include "stdafx.h"

/*
    Get cost of insertion Req1 before Req2
 */
LONGLONG
NTAPI
UniataGetCost(
    PHW_LU_EXTENSION LunExt,
    IN PATA_REQ AtaReq1,
    IN PATA_REQ AtaReq2
    )
{
    BOOLEAN write1;
    BOOLEAN write2;
    UCHAR flags1;
    UCHAR flags2;
    LONGLONG cost;
    // can't insert Req1 before tooooo old Req2
    if(!AtaReq2->ttl)
        return REORDER_COST_TTL;
    // check if reorderable
    flags1 = AtaReq1->Flags;
    flags2 = AtaReq2->Flags;
    if(!((flags2 & flags1) & REQ_FLAG_REORDERABLE_CMD))
        return REORDER_COST_DENIED;
    // if at least one Req is WRITE, target areas
    // can not intersect
    write1 = (flags1 & REQ_FLAG_RW_MASK) == REQ_FLAG_WRITE;
    write2 = (flags2 & REQ_FLAG_RW_MASK) == REQ_FLAG_WRITE;
    cost = AtaReq1->lba+AtaReq1->bcount - AtaReq2->lba;
    if( write1 || write2 ) {
        // check for intersection
        if((AtaReq1->lba < AtaReq2->lba+AtaReq2->bcount) &&
           (AtaReq1->lba+AtaReq1->bcount > AtaReq2->lba)) {
            // Intersection...
            return REORDER_COST_INTERSECT;
        }
    }
    if(cost < 0) {
        cost *= (1-LunExt->SeekBackMCost);
    } else {
        cost *= (LunExt->SeekBackMCost-1);
    }
    if( write1 == write2 ) {
        return cost;
    }
    return (cost * LunExt->RwSwitchMCost) + LunExt->RwSwitchCost;
} // end UniataGetCost()

/*
    Insert command to proper place of command queue
    Perform reorder if necessary
 */
VOID
NTAPI
UniataQueueRequest(
    IN PHW_CHANNEL chan,
    IN PSCSI_REQUEST_BLOCK Srb
    )
{
    PATA_REQ AtaReq = (PATA_REQ)(Srb->SrbExtension);
    PATA_REQ AtaReq1;
    PATA_REQ AtaReq2;

    LONGLONG best_cost;
    LONGLONG new_cost;
    LONGLONG new_cost1;
    LONGLONG new_cost2;
    PATA_REQ BestAtaReq1;

    BOOLEAN use_reorder = chan->UseReorder/*EnableReorder*/;
#ifdef QUEUE_STATISTICS
    BOOLEAN reordered = FALSE;
#endif //QUEUE_STATISTICS

    PHW_LU_EXTENSION LunExt = chan->lun[GET_LDEV(Srb) & 1];
    AtaReq->Srb = Srb;

/*
#ifdef _DEBUG
    if(!LunExt) {
        PrintNtConsole("q: chan = %#x, dev %#x\n", chan, GET_LDEV(Srb));
        int i;
        for(i=0; i<1000; i++) {
            AtapiStallExecution(5*1000);
        }
        return;
    }
#endif //_DEBUG
*/
    // check if queue is empty
    if(LunExt->queue_depth) {
        AtaReq->ttl = (UCHAR)(max(LunExt->queue_depth, MIN_REQ_TTL));

        // init loop
        BestAtaReq1 =
        AtaReq2 = LunExt->last_req;

        if(use_reorder &&
           (Srb->SrbFlags & SRB_FLAGS_QUEUE_ACTION_ENABLE)) {
            switch(Srb->QueueAction) {
            case SRB_ORDERED_QUEUE_TAG_REQUEST:
                use_reorder = FALSE;
#ifdef QUEUE_STATISTICS
                chan->TryReorderTailCount++;
#endif //QUEUE_STATISTICS
                break;
            case SRB_HEAD_OF_QUEUE_TAG_REQUEST:
                BestAtaReq1 = LunExt->first_req;
                best_cost = -REORDER_COST_RESELECT;
#ifdef QUEUE_STATISTICS
                chan->TryReorderHeadCount++;
#endif //QUEUE_STATISTICS
                break;
            case SRB_SIMPLE_TAG_REQUEST:
            default:
                best_cost = UniataGetCost(LunExt, BestAtaReq1, AtaReq);
                use_reorder |= TRUE;
            }
        } else
        if(use_reorder) {
            best_cost = UniataGetCost(LunExt, BestAtaReq1, AtaReq);
        }

        if(use_reorder) {

#ifdef QUEUE_STATISTICS
            chan->TryReorderCount++;
#endif //QUEUE_STATISTICS

            // walk through command queue and find the best
            // place for insertion of the command
            while ((AtaReq1 = AtaReq2->prev_req)) {
                new_cost1 = UniataGetCost(LunExt, AtaReq1, AtaReq);
                new_cost2 = UniataGetCost(LunExt, AtaReq, AtaReq2);

#ifdef QUEUE_STATISTICS
                if(new_cost1 == REORDER_COST_INTERSECT ||
                   new_cost2 == REORDER_COST_INTERSECT)
                    chan->IntersectCount++;
#endif //QUEUE_STATISTICS

                if(new_cost2 > REORDER_COST_RESELECT)
                    break;

                // for now I see nothing bad in RESELECT here
                //ASSERT(new_cost1 <= REORDER_COST_RESELECT);

                new_cost = UniataGetCost(LunExt, AtaReq1, AtaReq2);
                new_cost = new_cost1 + new_cost2 - new_cost;

                // check for Stop Reordering
                if(new_cost > REORDER_COST_RESELECT*3)
                    break;

                if(new_cost < best_cost) {
                    best_cost = new_cost;
                    BestAtaReq1 = AtaReq1;
#ifdef QUEUE_STATISTICS
                    reordered = TRUE;
#endif //QUEUE_STATISTICS
                }
                AtaReq2 = AtaReq1;
            }
#ifdef QUEUE_STATISTICS
            if(reordered)
                chan->ReorderCount++;
#endif //QUEUE_STATISTICS
        }
        // Insert Req between Req2 & Req1
        AtaReq2 = BestAtaReq1->next_req;
        if(AtaReq2) {
            AtaReq2->prev_req = AtaReq;
            AtaReq->next_req = AtaReq2;
        } else {
            AtaReq->next_req = NULL;
            LunExt->last_req = AtaReq;
        }
//        LunExt->last_req->next_req = AtaReq;
        BestAtaReq1->next_req = AtaReq;
//        AtaReq->prev_req = LunExt->last_req;
        AtaReq->prev_req = BestAtaReq1;

        AtaReq1 = AtaReq;
        while((AtaReq1 = AtaReq1->next_req)) {
            //ASSERT(AtaReq1->ttl);
            AtaReq1->ttl--;
        }

    } else {
        // empty queue
        AtaReq->ttl = 0;
        AtaReq->prev_req =
        AtaReq->next_req = NULL;
        LunExt->first_req =
        LunExt->last_req = AtaReq;
    }
    LunExt->queue_depth++;
    chan->queue_depth++;
    chan->DeviceExtension->queue_depth++;
    // check if this is the 1st request in queue
    if(chan->queue_depth == 1) {
        chan->cur_req = LunExt->first_req;
    }

#ifdef QUEUE_STATISTICS
    //ASSERT(LunExt->queue_depth);
    chan->QueueStat[min(MAX_QUEUE_STAT, LunExt->queue_depth)-1]++;
#endif //QUEUE_STATISTICS
/*
    ASSERT(chan->queue_depth ==
            (chan->lun[0]->queue_depth + chan->lun[1]->queue_depth));
    ASSERT(!chan->queue_depth || chan->cur_req);
*/
    return;
} // end UniataQueueRequest()

/*
    Remove request from queue and get next request
 */
VOID
NTAPI
UniataRemoveRequest(
    IN PHW_CHANNEL chan,
    IN PSCSI_REQUEST_BLOCK Srb
    )
{
    if(!Srb)
        return;
    if(!chan)
        return;

    PATA_REQ AtaReq = (PATA_REQ)(Srb->SrbExtension);
    //PHW_DEVICE_EXTENSION deviceExtension = chan->DeviceExtension;

    ULONG cdev = GET_LDEV(Srb) & 1;
    PHW_LU_EXTENSION LunExt = chan->lun[cdev];

    if(!LunExt)
        return;

/*
    ASSERT(chan->queue_depth ==
            (chan->lun[0]->queue_depth + chan->lun[1]->queue_depth));
    ASSERT(!chan->queue_depth || chan->cur_req);
*/
    // check if queue for the device is empty
    if(!LunExt->queue_depth)
        return;

    // check if request is under processing (busy)
    if(!AtaReq->ReqState)
        return;

    // remove reqest from queue
    if(AtaReq->prev_req) {
        AtaReq->prev_req->next_req =
            AtaReq->next_req;
    } else {
        LunExt->first_req = AtaReq->next_req;
    }
    if(AtaReq->next_req) {
        AtaReq->next_req->prev_req =
            AtaReq->prev_req;
    } else {
        LunExt->last_req = AtaReq->prev_req;
    }
    LunExt->queue_depth--;
    chan->queue_depth--;
    chan->DeviceExtension->queue_depth--;
    // set LastWrite flag for Lun
    LunExt->last_write = ((AtaReq->Flags & REQ_FLAG_RW_MASK) == REQ_FLAG_WRITE);

    // get request from longest queue to balance load
    if(chan->lun[0]->queue_depth * (chan->lun[0]->LunSelectWaitCount+1) >
       chan->lun[1]->queue_depth * (chan->lun[1]->LunSelectWaitCount+1)) {
        cdev = 0;
    } else {
        cdev = 1;
    }
/*    // prevent too long wait for actively used device
    if(chan->lun[cdev ^ 1]->queue_depth &&
       chan->lun[cdev ^ 1]->LunSelectWaitCount >= chan->lun[cdev]->queue_depth) {
        cdev = cdev ^ 1;
    }*/
    // get next request for processing
    chan->cur_req = chan->lun[cdev]->first_req;
    chan->cur_cdev = cdev;
    if(!chan->lun[cdev ^ 1]->queue_depth) {
        chan->lun[cdev ^ 1]->LunSelectWaitCount=0;
    } else {
        chan->lun[cdev ^ 1]->LunSelectWaitCount++;
    }
    chan->lun[cdev]->LunSelectWaitCount=0;

//    chan->first_req->prev_req = NULL;
    AtaReq->ReqState = REQ_STATE_NONE;
/*
    ASSERT(chan->queue_depth ==
            (chan->lun[0]->queue_depth + chan->lun[1]->queue_depth));
    ASSERT(!chan->queue_depth || chan->cur_req);
*/
    return;
} // end UniataRemoveRequest()

/*
    Get currently processed request
    (from head of the queue)
 */
PSCSI_REQUEST_BLOCK
NTAPI
UniataGetCurRequest(
    IN PHW_CHANNEL chan
    )
{
//    if(!chan->lun[]->queue_depth) {
    if(!chan || !chan->cur_req) {
        return NULL;
    }

    return chan->cur_req->Srb;
} // end UniataGetCurRequest()

/*
    Get next channel to be serviced
    (used in simplex mode only)
 */
PHW_CHANNEL
NTAPI
UniataGetNextChannel(
    IN PHW_CHANNEL chan
    )
{
    ULONG c=0, _c;
    PHW_DEVICE_EXTENSION deviceExtension;
    ULONG best_c;
    ULONG cost_c;

    deviceExtension = chan->DeviceExtension;

    if(!deviceExtension->simplexOnly) {
        return chan;
    }
    KdPrint2((PRINT_PREFIX "UniataGetNextChannel:\n"));
    best_c = -1;
    cost_c = 0;
    for(_c=0; _c<deviceExtension->NumberChannels; _c++) {
        c = (_c+deviceExtension->FirstChannelToCheck) % deviceExtension->NumberChannels;
        chan = &deviceExtension->chan[c];
        if(chan->queue_depth &&
           chan->queue_depth * (chan->ChannelSelectWaitCount+1) >
           cost_c) {
            best_c = c;
            cost_c = chan->queue_depth * (chan->ChannelSelectWaitCount+1);
        }
    }
    if(best_c == CHAN_NOT_SPECIFIED) {
        KdPrint2((PRINT_PREFIX "  empty queues\n"));
        return NULL;
    }
    deviceExtension->FirstChannelToCheck = c;
    for(_c=0; _c<deviceExtension->NumberChannels; _c++) {
        chan = &deviceExtension->chan[_c];
        if(_c == best_c) {
            chan->ChannelSelectWaitCount = 0;
            continue;
        }
        chan->ChannelSelectWaitCount++;
        if(!chan->queue_depth) {
            chan->ChannelSelectWaitCount = 0;
        } else {
            chan->ChannelSelectWaitCount++;
        }
    }
    KdPrint2((PRINT_PREFIX "  select chan %d\n", best_c));
    return &deviceExtension->chan[best_c];
} // end UniataGetNextChannel()
