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    <div class="moz-cite-prefix">I just realized that a change I'm
      thinking about for a while would solve your problem as well, but
      keep concurrent allocation possible.<br>
      <br>
      See ttm_mem_evict_first() unlocks the BO after evicting it:<br>
      <blockquote type="cite">        ttm_bo_del_from_lru(bo);<br>
                spin_unlock(&glob->lru_lock);<br>
        <br>
                ret = ttm_bo_evict(bo, ctx);<br>
                if (locked) {<br>
                        ttm_bo_unreserve(bo); <-------- here<br>
                } else {<br>
                        spin_lock(&glob->lru_lock);<br>
                        ttm_bo_add_to_lru(bo);<br>
                        spin_unlock(&glob->lru_lock);<br>
                }<br>
        <br>
                kref_put(&bo->list_kref, ttm_bo_release_list);<br>
      </blockquote>
      <br>
      The effect is that in your example process C can not only beat
      process B once, but many many times because we run into a
      ping/pong situation where B evicts resources while C moves them
      back in.<br>
      <br>
      For a while now I'm thinking about dropping those reservations
      only after the original allocation succeeded.<br>
      <br>
      The effect would be that process C can still beat process B
      initially, but sooner or process B would evict some resources from
      process C as well and then it can succeed with its allocation.<br>
      <br>
      The problem is for this approach to work we need to core change to
      the ww_mutexes to be able to handle this efficiently.<br>
      <br>
      Regards,<br>
      Christian.<br>
      <br>
      Am 26.01.2018 um 14:59 schrieb Christian König:<br>
    </div>
    <blockquote type="cite"
      cite="mid:e3ed22b7-ca1a-09d0-47a0-204affef780f@amd.com">
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
      <div class="moz-cite-prefix">I know, but this has the same effect.
        You prevent concurrent allocation from happening.<br>
        <br>
        What we could do is to pipeline reusing of deleted memory as
        well, this makes it less likely to cause the problem you are
        seeing because the evicting processes doesn't need to block for
        deleted BOs any more.<br>
        <br>
        But that other processes can grab memory during eviction is
        intentional. Otherwise greedy processes would completely
        dominate command submission.<br>
        <br>
        Regards,<br>
        Christian.<br>
        <br>
        Am 26.01.2018 um 14:50 schrieb Zhou, David(ChunMing):<br>
      </div>
      <blockquote type="cite" cite="mid:smartisan1516974623698">
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        <div name="smartisanmessageid" id="smartisan1516974623698"><font
            color="#333333">I don't want to prevent all, my new approach
            is to prevent the later allocation is trying and ahead of
            front to get the memory space that the front made from
            eviction. <br>
          </font><br>
          <br>
          <span id="smartisan_signature" style="font-size:0.8em;
            display:inline; color:#888888">
            <p dir="ltr">发自坚果 Pro</p>
          </span>
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          <div class="quote">
            <div style="margin:0 0px; font-size:105%"><font
                style="line-height:1.4" color="#629140"><span>Christian
                  K鰊ig <a class="moz-txt-link-rfc2396E"
                    href="mailto:ckoenig.leichtzumerken@gmail.com"
                    moz-do-not-send="true"><ckoenig.leichtzumerken@gmail.com></a>
                  于 2018年1月26日 下午9:24写道:</span></font></div>
            <br type="attribution">
          </div>
        </div>
        <div>
          <div class="moz-cite-prefix">Yes, exactly that's the problem.<br>
            <br>
            See when you want to prevent a process B from allocating the
            memory process A has evicted, you need to prevent all
            concurrent allocation.<br>
            <br>
            And we don't do that because it causes a major performance
            drop.<br>
            <br>
            Regards,<br>
            Christian.<br>
            <br>
            Am 26.01.2018 um 14:21 schrieb Zhou, David(ChunMing):<br>
          </div>
          <blockquote type="cite">
            <meta content="text/html; charset=utf-8">
            <div name="smartisanmessageid" id="smartisan1516972869817"><font
                color="#333333">You patch will prevent concurrent
                allocation, and will result in allocation performance
                drop much.</font><br>
              <br>
              <span id="smartisan_signature" style="font-size:0.8em;
                display:inline; color:#888888">
                <p dir="ltr">发自坚果 Pro</p>
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              <div class="quote">
                <div style="margin:0 0px; font-size:105%"><font
                    style="line-height:1.4" color="#629140"><span>Christian
                      K鰊ig <a class="moz-txt-link-rfc2396E"
                        href="mailto:ckoenig.leichtzumerken@gmail.com"
                        moz-do-not-send="true"><ckoenig.leichtzumerken@gmail.com></a>
                      于 2018年1月26日 下午9:04写道:</span></font></div>
                <br type="attribution">
              </div>
            </div>
            <div>
              <div class="moz-cite-prefix">Attached is what you actually
                want to do cleanly implemented. But as I said this is a
                NO-GO.<br>
                <br>
                Regards,<br>
                Christian.<br>
                <br>
                Am 26.01.2018 um 13:43 schrieb Christian König:<br>
              </div>
              <blockquote type="cite">
                <div class="moz-cite-prefix">
                  <blockquote type="cite">After my investigation, this
                    issue should be detect of TTM design self, which
                    breaks scheduling balance.<br>
                  </blockquote>
                  Yeah, but again. This is indented design we can't
                  change easily.<br>
                  <br>
                  Regards,<br>
                  Christian.<br>
                  <br>
                  Am 26.01.2018 um 13:36 schrieb Zhou, David(ChunMing):<br>
                </div>
                <blockquote type="cite">
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                  <div>
                    <div name="x_smartisanmessageid"
                      id="x_smartisan1516970199102"><font
                        color="#333333">I am off work, so reply mail by
                        phone, the format could not be text.<br>
                      </font><br>
                      back to topic itself:<br>
                      the problem indeed happen on amdgpu driver,
                      someone reports me that application runs with two
                      instances, the performance are different.<br>
                      I also reproduced the issue with unit
                      test(bo_eviction_test). They always think our
                      scheduler isn't working as expected.<br>
                      <br>
                      After my investigation, this issue should be
                      detect of TTM design self, which breaks scheduling
                      balance.<br>
                      <br>
                      Further, if we run containers for our gpu,
                      container A could run high score, container B runs
                      low score with same benchmark.<br>
                      <br>
                      So this is bug that we need fix.<br>
                      <br>
                      Regards,<br>
                      David Zhou<br>
                      <br>
                      <span id="x_smartisan_signature"
                        style="font-size:0.8em; display:inline;
                        color:#888888">
                        <p dir="ltr">发自坚果 Pro</p>
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                      <div class="x_quote">
                        <div style="margin:0 0px; font-size:105%"><font
                            style="line-height:1.4" color="#629140"><span>Christian
                              K鰊ig <a class="moz-txt-link-rfc2396E"
                                href="mailto:ckoenig.leichtzumerken@gmail.com"
                                moz-do-not-send="true"><ckoenig.leichtzumerken@gmail.com></a>
                              于 2018年1月26日 下午6:31写道:</span></font></div>
                        <br type="attribution">
                      </div>
                    </div>
                  </div>
                  <font size="2"><span style="font-size:11pt">
                      <div class="PlainText">Am 26.01.2018 um 11:22
                        schrieb Chunming Zhou:<br>
                        > there is a scheduling balance issue about
                        get node like:<br>
                        > a. process A allocates full memory and use
                        it for submission.<br>
                        > b. process B tries to allocates memory,
                        will wait for process A BO idle in eviction.<br>
                        > c. process A completes the job, process B
                        eviction will put process A BO node,<br>
                        > but in the meantime, process C is comming
                        to allocate BO, whill directly get node
                        successfully, and do submission,<br>
                        > process B will again wait for process C BO
                        idle.<br>
                        > d. repeat the above setps, process B could
                        be delayed much more.<br>
                        ><br>
                        > later allocation must not be ahead of front
                        in same place.<br>
                        <br>
                        Again NAK to the whole approach.<br>
                        <br>
                        At least with amdgpu the problem you described
                        above never occurs <br>
                        because evictions are pipelined operations. We
                        could only block for <br>
                        deleted regions to become free.<br>
                        <br>
                        But independent of that incoming memory requests
                        while we make room for <br>
                        eviction are intended to be served first.<br>
                        <br>
                        Changing that is certainly a no-go cause that
                        would favor memory hungry <br>
                        applications over small clients.<br>
                        <br>
                        Regards,<br>
                        Christian.<br>
                        <br>
                        ><br>
                        > Change-Id:
                        I3daa892e50f82226c552cc008a29e55894a98f18<br>
                        > Signed-off-by: Chunming Zhou <a
                          class="moz-txt-link-rfc2396E"
                          href="mailto:david1.zhou@amd.com"
                          moz-do-not-send="true">
                          <david1.zhou@amd.com></a><br>
                        > ---<br>
                        >   drivers/gpu/drm/ttm/ttm_bo.c    | 69
                        +++++++++++++++++++++++++++++++++++++++--<br>
                        >   include/drm/ttm/ttm_bo_api.h    |  7
                        +++++<br>
                        >   include/drm/ttm/ttm_bo_driver.h |  7
                        +++++<br>
                        >   3 files changed, 80 insertions(+), 3
                        deletions(-)<br>
                        ><br>
                        > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
                        b/drivers/gpu/drm/ttm/ttm_bo.c<br>
                        > index d33a6bb742a1..558ec2cf465d 100644<br>
                        > --- a/drivers/gpu/drm/ttm/ttm_bo.c<br>
                        > +++ b/drivers/gpu/drm/ttm/ttm_bo.c<br>
                        > @@ -841,6 +841,58 @@ static int
                        ttm_bo_add_move_fence(struct ttm_buffer_object
                        *bo,<br>
                        >        return 0;<br>
                        >   }<br>
                        >   <br>
                        > +static void ttm_man_init_waiter(struct
                        ttm_bo_waiter *waiter,<br>
                        > +                             struct
                        ttm_buffer_object *bo,<br>
                        > +                             const struct
                        ttm_place *place)<br>
                        > +{<br>
                        > +     waiter->tbo = bo;<br>
                        > +     memcpy((void *)&waiter->place,
                        (void *)place, sizeof(*place));<br>
                        > +     INIT_LIST_HEAD(&waiter->list);<br>
                        > +}<br>
                        > +<br>
                        > +static void ttm_man_add_waiter(struct
                        ttm_mem_type_manager *man,<br>
                        > +                            struct
                        ttm_bo_waiter *waiter)<br>
                        > +{<br>
                        > +     if (!waiter)<br>
                        > +             return;<br>
                        > +     spin_lock(&man->wait_lock);<br>
                        > +     list_add_tail(&waiter->list,
                        &man->waiter_list);<br>
                        > +     spin_unlock(&man->wait_lock);<br>
                        > +}<br>
                        > +<br>
                        > +static void ttm_man_del_waiter(struct
                        ttm_mem_type_manager *man,<br>
                        > +                            struct
                        ttm_bo_waiter *waiter)<br>
                        > +{<br>
                        > +     if (!waiter)<br>
                        > +             return;<br>
                        > +     spin_lock(&man->wait_lock);<br>
                        > +     if
                        (!list_empty(&waiter->list))<br>
                        > +            
                        list_del(&waiter->list);<br>
                        > +     spin_unlock(&man->wait_lock);<br>
                        > +     kfree(waiter);<br>
                        > +}<br>
                        > +<br>
                        > +int ttm_man_check_bo(struct
                        ttm_mem_type_manager *man,<br>
                        > +                  struct ttm_buffer_object
                        *bo,<br>
                        > +                  const struct ttm_place
                        *place)<br>
                        > +{<br>
                        > +     struct ttm_bo_waiter *waiter, *tmp;<br>
                        > +<br>
                        > +     spin_lock(&man->wait_lock);<br>
                        > +     list_for_each_entry_safe(waiter, tmp,
                        &man->waiter_list, list) {<br>
                        > +             if ((bo != waiter->tbo)
                        &&<br>
                        > +                 ((place->fpfn >=
                        waiter->place.fpfn &&<br>
                        > +                   place->fpfn <=
                        waiter->place.lpfn) ||<br>
                        > +                  (place->lpfn <=
                        waiter->place.lpfn && place->lpfn
                        >=<br>
                        > +                  
                        waiter->place.fpfn)))<br>
                        > +                 goto later_bo;<br>
                        > +     }<br>
                        > +     spin_unlock(&man->wait_lock);<br>
                        > +     return true;<br>
                        > +later_bo:<br>
                        > +     spin_unlock(&man->wait_lock);<br>
                        > +     return false;<br>
                        > +}<br>
                        >   /**<br>
                        >    * Repeatedly evict memory from the LRU
                        for @mem_type until we create enough<br>
                        >    * space, or we've evicted everything and
                        there isn't enough space.<br>
                        > @@ -853,17 +905,26 @@ static int
                        ttm_bo_mem_force_space(struct ttm_buffer_object
                        *bo,<br>
                        >   {<br>
                        >        struct ttm_bo_device *bdev =
                        bo->bdev;<br>
                        >        struct ttm_mem_type_manager *man =
                        &bdev->man[mem_type];<br>
                        > +     struct ttm_bo_waiter waiter;<br>
                        >        int ret;<br>
                        >   <br>
                        > +     ttm_man_init_waiter(&waiter, bo,
                        place);<br>
                        > +     ttm_man_add_waiter(man, &waiter);<br>
                        >        do {<br>
                        >                ret =
                        (*man->func->get_node)(man, bo, place,
                        mem);<br>
                        > -             if (unlikely(ret != 0))<br>
                        > +             if (unlikely(ret != 0)) {<br>
                        > +                    
                        ttm_man_del_waiter(man, &waiter);<br>
                        >                        return ret;<br>
                        > -             if (mem->mm_node)<br>
                        > +             }<br>
                        > +             if (mem->mm_node) {<br>
                        > +                    
                        ttm_man_del_waiter(man, &waiter);<br>
                        >                        break;<br>
                        > +             }<br>
                        >                ret =
                        ttm_mem_evict_first(bdev, mem_type, place, ctx);<br>
                        > -             if (unlikely(ret != 0))<br>
                        > +             if (unlikely(ret != 0)) {<br>
                        > +                    
                        ttm_man_del_waiter(man, &waiter);<br>
                        >                        return ret;<br>
                        > +             }<br>
                        >        } while (1);<br>
                        >        mem->mem_type = mem_type;<br>
                        >        return ttm_bo_add_move_fence(bo,
                        man, mem);<br>
                        > @@ -1450,6 +1511,8 @@ int
                        ttm_bo_init_mm(struct ttm_bo_device *bdev,
                        unsigned type,<br>
                        >        man->use_io_reserve_lru = false;<br>
                        >       
                        mutex_init(&man->io_reserve_mutex);<br>
                        >       
                        spin_lock_init(&man->move_lock);<br>
                        > +    
                        spin_lock_init(&man->wait_lock);<br>
                        > +    
                        INIT_LIST_HEAD(&man->waiter_list);<br>
                        >       
                        INIT_LIST_HEAD(&man->io_reserve_lru);<br>
                        >   <br>
                        >        ret =
                        bdev->driver->init_mem_type(bdev, type,
                        man);<br>
                        > diff --git a/include/drm/ttm/ttm_bo_api.h
                        b/include/drm/ttm/ttm_bo_api.h<br>
                        > index 2cd025c2abe7..0fce4dbd02e7 100644<br>
                        > --- a/include/drm/ttm/ttm_bo_api.h<br>
                        > +++ b/include/drm/ttm/ttm_bo_api.h<br>
                        > @@ -40,6 +40,7 @@<br>
                        >   #include <linux/mm.h><br>
                        >   #include <linux/bitmap.h><br>
                        >   #include <linux/reservation.h><br>
                        > +#include <drm/ttm/ttm_placement.h><br>
                        >   <br>
                        >   struct ttm_bo_device;<br>
                        >   <br>
                        > @@ -232,6 +233,12 @@ struct
                        ttm_buffer_object {<br>
                        >        struct mutex wu_mutex;<br>
                        >   };<br>
                        >   <br>
                        > +struct ttm_bo_waiter {<br>
                        > +     struct ttm_buffer_object *tbo;<br>
                        > +     struct ttm_place place;<br>
                        > +     struct list_head list;<br>
                        > +};<br>
                        > +<br>
                        >   /**<br>
                        >    * struct ttm_bo_kmap_obj<br>
                        >    *<br>
                        > diff --git
                        a/include/drm/ttm/ttm_bo_driver.h
                        b/include/drm/ttm/ttm_bo_driver.h<br>
                        > index 9b417eb2df20..dc6b8b4c9e06 100644<br>
                        > --- a/include/drm/ttm/ttm_bo_driver.h<br>
                        > +++ b/include/drm/ttm/ttm_bo_driver.h<br>
                        > @@ -293,6 +293,10 @@ struct
                        ttm_mem_type_manager {<br>
                        >        bool io_reserve_fastpath;<br>
                        >        spinlock_t move_lock;<br>
                        >   <br>
                        > +     /* waiters in list */<br>
                        > +     spinlock_t wait_lock;<br>
                        > +     struct list_head waiter_list;<br>
                        > +<br>
                        >        /*<br>
                        >         * Protected by @io_reserve_mutex:<br>
                        >         */<br>
                        > @@ -748,6 +752,9 @@ int
                        ttm_bo_mem_space(struct ttm_buffer_object *bo,<br>
                        >                     struct ttm_mem_reg
                        *mem,<br>
                        >                     struct
                        ttm_operation_ctx *ctx);<br>
                        >   <br>
                        > +int ttm_man_check_bo(struct
                        ttm_mem_type_manager *man,<br>
                        > +                  struct ttm_buffer_object
                        *bo,<br>
                        > +                  const struct ttm_place
                        *place);<br>
                        >   void ttm_bo_mem_put(struct
                        ttm_buffer_object *bo, struct ttm_mem_reg *mem);<br>
                        >   void ttm_bo_mem_put_locked(struct
                        ttm_buffer_object *bo,<br>
                        >                           struct
                        ttm_mem_reg *mem);<br>
                        <br>
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