* Why do flush page cache twice when change TT's cache attribute
@ 2012-03-19 15:11 Scott Fang
2012-03-19 15:13 ` Scott Fang
2012-03-19 17:22 ` Jerome Glisse
0 siblings, 2 replies; 6+ messages in thread
From: Scott Fang @ 2012-03-19 15:11 UTC (permalink / raw)
To: dri-devel
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In function ttm_tt_set_caching
,,,,,,,
if (ttm->caching_state == tt_cached)
drm_clflush_pages(ttm->pages, ttm->num_pages);
for (i = 0; i < ttm->num_pages; ++i) {
cur_page = ttm->pages[i];
if (likely(cur_page != NULL)) {
ret = ttm_tt_set_page_caching(cur_page,
ttm->caching_state,
c_state);
if (unlikely(ret != 0))
goto out_err;
}
}
ttm->caching_state = c_state;
return 0;
drm_clflush_pages flush cache one time.
then in the following function
ttm_tt_set_page_caching->set_memory_wc->change_page_attr_set:
in this function may flush page cache again.
Does the code do some abundant flush, or there is some trick to these codes?
Thanks for the answer in advance.
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Why do flush page cache twice when change TT's cache attribute
2012-03-19 15:11 Why do flush page cache twice when change TT's cache attribute Scott Fang
@ 2012-03-19 15:13 ` Scott Fang
2012-03-19 17:22 ` Jerome Glisse
1 sibling, 0 replies; 6+ messages in thread
From: Scott Fang @ 2012-03-19 15:13 UTC (permalink / raw)
To: dri-devel
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typo error. abundant=>redundant
2012/3/19 Scott Fang <donnie.fang@gmail.com>
> In function ttm_tt_set_caching
> ,,,,,,,
>
> if (ttm->caching_state == tt_cached)
> drm_clflush_pages(ttm->pages, ttm->num_pages);
>
> for (i = 0; i < ttm->num_pages; ++i) {
> cur_page = ttm->pages[i];
> if (likely(cur_page != NULL)) {
> ret = ttm_tt_set_page_caching(cur_page,
> ttm->caching_state,
> c_state);
> if (unlikely(ret != 0))
> goto out_err;
> }
> }
>
> ttm->caching_state = c_state;
>
> return 0;
>
>
> drm_clflush_pages flush cache one time.
> then in the following function ttm_tt_set_page_caching->set_memory_wc->change_page_attr_set:
> in this function may flush page cache again.
>
> Does the code do some redundant flush, or there is some trick to these
> codes?
>
> Thanks for the answer in advance.
>
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Why do flush page cache twice when change TT's cache attribute
2012-03-19 15:11 Why do flush page cache twice when change TT's cache attribute Scott Fang
2012-03-19 15:13 ` Scott Fang
@ 2012-03-19 17:22 ` Jerome Glisse
2012-03-20 2:15 ` Scott Fang
1 sibling, 1 reply; 6+ messages in thread
From: Jerome Glisse @ 2012-03-19 17:22 UTC (permalink / raw)
To: Scott Fang; +Cc: dri-devel
On Mon, 2012-03-19 at 23:11 +0800, Scott Fang wrote:
> In function ttm_tt_set_caching
> ,,,,,,,
>
> if (ttm->caching_state == tt_cached)
> drm_clflush_pages(ttm->pages, ttm->num_pages);
>
> for (i = 0; i < ttm->num_pages; ++i) {
> cur_page = ttm->pages[i];
> if (likely(cur_page != NULL)) {
> ret = ttm_tt_set_page_caching(cur_page,
> ttm->caching_state,
> c_state);
> if (unlikely(ret != 0))
> goto out_err;
> }
> }
>
> ttm->caching_state = c_state;
>
> return 0;
>
>
> drm_clflush_pages flush cache one time.
> then in the following function
> ttm_tt_set_page_caching->set_memory_wc->change_page_attr_set: in this
> function may flush page cache again.
>
> Does the code do some abundant flush, or there is some trick to these
> codes?
>
> Thanks for the answer in advance.
Yes there might be redundant flushing.
Cheers,
Jerome
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Why do flush page cache twice when change TT's cache attribute
2012-03-19 17:22 ` Jerome Glisse
@ 2012-03-20 2:15 ` Scott Fang
2012-03-20 15:33 ` Konrad Rzeszutek Wilk
0 siblings, 1 reply; 6+ messages in thread
From: Scott Fang @ 2012-03-20 2:15 UTC (permalink / raw)
To: Jerome Glisse; +Cc: dri-devel
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Can I do the optimization like:
if (ttm->caching_state == tt_cached)
- drm_clflush_pages(ttm->pages, ttm->num_pages);
+ for (i = 0; i < ttm->num_pages; ++i)
+ if (PageHighMem(ttm->pages[i]))
+ drm_clflush_pages(&ttm->pages[i], 1);
only do flush cache when high memory and leave the linear memory flush in
function set_memory_uc/wc?
2012/3/20 Jerome Glisse <j.glisse@gmail.com>
> On Mon, 2012-03-19 at 23:11 +0800, Scott Fang wrote:
> > In function ttm_tt_set_caching
> > ,,,,,,,
> >
> > if (ttm->caching_state == tt_cached)
> > drm_clflush_pages(ttm->pages, ttm->num_pages);
> >
> > for (i = 0; i < ttm->num_pages; ++i) {
> > cur_page = ttm->pages[i];
> > if (likely(cur_page != NULL)) {
> > ret = ttm_tt_set_page_caching(cur_page,
> > ttm->caching_state,
> > c_state);
> > if (unlikely(ret != 0))
> > goto out_err;
> > }
> > }
> >
> > ttm->caching_state = c_state;
> >
> > return 0;
> >
> >
> > drm_clflush_pages flush cache one time.
> > then in the following function
> > ttm_tt_set_page_caching->set_memory_wc->change_page_attr_set: in this
> > function may flush page cache again.
> >
> > Does the code do some abundant flush, or there is some trick to these
> > codes?
> >
> > Thanks for the answer in advance.
>
> Yes there might be redundant flushing.
>
> Cheers,
> Jerome
>
>
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Why do flush page cache twice when change TT's cache attribute
2012-03-20 2:15 ` Scott Fang
@ 2012-03-20 15:33 ` Konrad Rzeszutek Wilk
2012-03-21 1:37 ` Scott Fang
0 siblings, 1 reply; 6+ messages in thread
From: Konrad Rzeszutek Wilk @ 2012-03-20 15:33 UTC (permalink / raw)
To: Scott Fang; +Cc: dri-devel
On Tue, Mar 20, 2012 at 10:15:02AM +0800, Scott Fang wrote:
> Can I do the optimization like:
>
> if (ttm->caching_state == tt_cached)
> - drm_clflush_pages(ttm->pages, ttm->num_pages);
> + for (i = 0; i < ttm->num_pages; ++i)
> + if (PageHighMem(ttm->pages[i]))
> + drm_clflush_pages(&ttm->pages[i], 1);
>
> only do flush cache when high memory and leave the linear memory flush in
> function set_memory_uc/wc?
So what are you trying to solve? I mean one way to fix this
is to do:
>
> 2012/3/20 Jerome Glisse <j.glisse@gmail.com>
>
> > On Mon, 2012-03-19 at 23:11 +0800, Scott Fang wrote:
> > > In function ttm_tt_set_caching
> > > ,,,,,,,
> > >
> > > if (ttm->caching_state == tt_cached)
> > > drm_clflush_pages(ttm->pages, ttm->num_pages);
goto out;
> > >
> > > for (i = 0; i < ttm->num_pages; ++i) {
> > > cur_page = ttm->pages[i];
> > > if (likely(cur_page != NULL)) {
> > > ret = ttm_tt_set_page_caching(cur_page,
> > > ttm->caching_state,
> > > c_state);
> > > if (unlikely(ret != 0))
> > > goto out_err;
> > > }
> > > }
> >
out:
> > > ttm->caching_state = c_state;
> > >
> > > return 0;
Is the problem with calling page change twice making the machine slow?
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Why do flush page cache twice when change TT's cache attribute
2012-03-20 15:33 ` Konrad Rzeszutek Wilk
@ 2012-03-21 1:37 ` Scott Fang
0 siblings, 0 replies; 6+ messages in thread
From: Scott Fang @ 2012-03-21 1:37 UTC (permalink / raw)
To: Konrad Rzeszutek Wilk; +Cc: dri-devel
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yes, flush page twice cause system slow in some CPU.
Meanwhile, set_memory_uc/wc doesn't only do flush page cache, but also
change page table attribute, so your solution seems to have some problem.
2012/3/20 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> On Tue, Mar 20, 2012 at 10:15:02AM +0800, Scott Fang wrote:
> > Can I do the optimization like:
> >
> > if (ttm->caching_state == tt_cached)
> > - drm_clflush_pages(ttm->pages, ttm->num_pages);
> > + for (i = 0; i < ttm->num_pages; ++i)
> > + if (PageHighMem(ttm->pages[i]))
> > + drm_clflush_pages(&ttm->pages[i], 1);
> >
> > only do flush cache when high memory and leave the linear memory flush in
> > function set_memory_uc/wc?
>
> So what are you trying to solve? I mean one way to fix this
> is to do:
> >
> > 2012/3/20 Jerome Glisse <j.glisse@gmail.com>
> >
> > > On Mon, 2012-03-19 at 23:11 +0800, Scott Fang wrote:
> > > > In function ttm_tt_set_caching
> > > > ,,,,,,,
> > > >
> > > > if (ttm->caching_state == tt_cached)
> > > > drm_clflush_pages(ttm->pages, ttm->num_pages);
> goto out;
> > > >
> > > > for (i = 0; i < ttm->num_pages; ++i) {
> > > > cur_page = ttm->pages[i];
> > > > if (likely(cur_page != NULL)) {
> > > > ret = ttm_tt_set_page_caching(cur_page,
> > > > ttm->caching_state,
> > > > c_state);
> > > > if (unlikely(ret != 0))
> > > > goto out_err;
> > > > }
> > > > }
> > >
> out:
> > > > ttm->caching_state = c_state;
> > > >
> > > > return 0;
>
> Is the problem with calling page change twice making the machine slow?
>
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^ permalink raw reply [flat|nested] 6+ messages in thread
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-- links below jump to the message on this page --
2012-03-19 15:11 Why do flush page cache twice when change TT's cache attribute Scott Fang
2012-03-19 15:13 ` Scott Fang
2012-03-19 17:22 ` Jerome Glisse
2012-03-20 2:15 ` Scott Fang
2012-03-20 15:33 ` Konrad Rzeszutek Wilk
2012-03-21 1:37 ` Scott Fang
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