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<div class="moz-cite-prefix">
<blockquote type="cite">So I think preventing validation on same
place is a simpler way:<br>
process B bo's place is fpfn~lpfn, it will only try to evict LRU
BOs in that range, while eviction, we just prevent those
validation to this range(fpfn~lpfn), if out of this range, the
allocation/validation still can be go on.<br>
<br>
Any negative?<br>
</blockquote>
That won't work either. The most common use of fpfn~lpfn range is
to limit a BO to visible VRAM, the other use cases are to fullfil
hardware limitations.<br>
<br>
So blocking this would result in blocking all normal GTT and VRAM
allocations, adding a mutex to validate would have the same
effect.<br>
<br>
Regards,<br>
Christian.<br>
<br>
Am 31.01.2018 um 11:30 schrieb Chunming Zhou:<br>
</div>
<blockquote type="cite"
cite="mid:cdb7726b-a82d-494c-a98c-ca0100f323cc@amd.com">
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<p><br>
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<br>
<div class="moz-cite-prefix">On 2018年01月26日 22:35, Christian König
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:a6d78bba-bbe9-769b-f9d3-665cdd8c04da@gmail.com">
<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>
</div>
</blockquote>
For ping/pong case, I want to disable busy placement for
allocation period, only enable it for cs bo validation.<br>
<br>
<blockquote type="cite"
cite="mid:a6d78bba-bbe9-769b-f9d3-665cdd8c04da@gmail.com">
<div class="moz-cite-prefix"> <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>
</div>
</blockquote>
If it is from process C cs validation, process B still need evict
the resource only after process C command submission completion.<br>
<br>
<blockquote type="cite"
cite="mid:a6d78bba-bbe9-769b-f9d3-665cdd8c04da@gmail.com">
<div class="moz-cite-prefix"> <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>
</div>
</blockquote>
Yes, ww_mutex doesn't support this net lock, which easily deadlock
without ticket and class.<br>
<br>
So I think preventing validation on same place is a simpler way:<br>
process B bo's place is fpfn~lpfn, it will only try to evict LRU
BOs in that range, while eviction, we just prevent those
validation to this range(fpfn~lpfn), if out of this range, the
allocation/validation still can be go on.<br>
<br>
Any negative?<br>
<br>
Regards,<br>
David Zhou<br>
<blockquote type="cite"
cite="mid:a6d78bba-bbe9-769b-f9d3-665cdd8c04da@gmail.com">
<div class="moz-cite-prefix"> <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">
<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">
<meta content="text/html; charset=utf-8">
<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>
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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>
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<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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