From: Mika Kuoppala <mika.kuoppala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Cc: igt-dev@lists.freedesktop.org, matthew.auld@intel.com
Subject: Re: [igt-dev] [Intel-gfx] [PATCH i-g-t 1/3] i915/gem_userptr_blits: Only mlock the memfd once, not the arena
Date: Wed, 16 Jan 2019 12:35:59 +0200 [thread overview]
Message-ID: <87o98gyjn4.fsf@gaia.fi.intel.com> (raw)
In-Reply-To: <154763269626.30063.2897361111833119934@skylake-alporthouse-com>
Chris Wilson <chris@chris-wilson.co.uk> writes:
> Quoting Mika Kuoppala (2019-01-16 09:47:27)
>> Chris Wilson <chris@chris-wilson.co.uk> writes:
>>
>> > We multiply the memfd 64k to create a 2G arena which we then attempt to
>> > write into after marking read-only. Howver, when it comes to unlock the
>>
>> s/Howver/However
>>
>> > arena after the test, performance tanks as the kernel tries to resolve
>> > the 64k repeated mappings onto the same set of pages. (Must not be a
>> > very common operation!) We can get away with just mlocking the backing
>> > store to prevent its eviction, which should prevent the arena mapping
>> > from being freed as well.
>>
>> hmm should. How are they bound?
>
> All I'm worried about are the allocs for the pud/pmd etc, which aiui are
> not freed until the pte are removed and the pte shouldn't be reaped
> because the struct page are locked. However, I haven't actually verified
> that mlocking the underlying pages is enough to be sure that the page
> tables of the various mappings are safe from eviction. On the other
> hand, munlock_vma_range doesn't scale to the abuse we put it to, and
> that is causing issues for CI!
If we can dodge it with this, great.
Noticed there is also typo in preceeding code,
the comment when mapping the arena. s/usuable/usable.
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
_______________________________________________
igt-dev mailing list
igt-dev@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/igt-dev
WARNING: multiple messages have this Message-ID (diff)
From: Mika Kuoppala <mika.kuoppala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Cc: igt-dev@lists.freedesktop.org, matthew.auld@intel.com
Subject: Re: [PATCH i-g-t 1/3] i915/gem_userptr_blits: Only mlock the memfd once, not the arena
Date: Wed, 16 Jan 2019 12:35:59 +0200 [thread overview]
Message-ID: <87o98gyjn4.fsf@gaia.fi.intel.com> (raw)
In-Reply-To: <154763269626.30063.2897361111833119934@skylake-alporthouse-com>
Chris Wilson <chris@chris-wilson.co.uk> writes:
> Quoting Mika Kuoppala (2019-01-16 09:47:27)
>> Chris Wilson <chris@chris-wilson.co.uk> writes:
>>
>> > We multiply the memfd 64k to create a 2G arena which we then attempt to
>> > write into after marking read-only. Howver, when it comes to unlock the
>>
>> s/Howver/However
>>
>> > arena after the test, performance tanks as the kernel tries to resolve
>> > the 64k repeated mappings onto the same set of pages. (Must not be a
>> > very common operation!) We can get away with just mlocking the backing
>> > store to prevent its eviction, which should prevent the arena mapping
>> > from being freed as well.
>>
>> hmm should. How are they bound?
>
> All I'm worried about are the allocs for the pud/pmd etc, which aiui are
> not freed until the pte are removed and the pte shouldn't be reaped
> because the struct page are locked. However, I haven't actually verified
> that mlocking the underlying pages is enough to be sure that the page
> tables of the various mappings are safe from eviction. On the other
> hand, munlock_vma_range doesn't scale to the abuse we put it to, and
> that is causing issues for CI!
If we can dodge it with this, great.
Noticed there is also typo in preceeding code,
the comment when mapping the arena. s/usuable/usable.
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
next prev parent reply other threads:[~2019-01-16 10:35 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 9:35 [igt-dev] [PATCH i-g-t 1/3] i915/gem_userptr_blits: Only mlock the memfd once, not the arena Chris Wilson
2019-01-16 9:35 ` Chris Wilson
2019-01-16 9:35 ` [igt-dev] [PATCH i-g-t 2/3] i915/gem_cpu_reloc: Use a self-modifying chained batch Chris Wilson
2019-01-16 9:35 ` Chris Wilson
2019-01-16 14:22 ` [igt-dev] [Intel-gfx] " Mika Kuoppala
2019-01-16 14:22 ` Mika Kuoppala
2019-01-16 14:30 ` [igt-dev] [Intel-gfx] " Chris Wilson
2019-01-16 14:30 ` Chris Wilson
2019-01-16 14:49 ` [igt-dev] [Intel-gfx] " Mika Kuoppala
2019-01-16 14:49 ` Mika Kuoppala
2019-01-16 9:35 ` [igt-dev] [PATCH i-g-t 3/3] igt/drv_missed_irq: Skip if the kernel reports no rings available to test Chris Wilson
2019-01-16 9:35 ` Chris Wilson
2019-01-16 14:30 ` [igt-dev] [Intel-gfx] " Mika Kuoppala
2019-01-16 14:30 ` Mika Kuoppala
2019-01-16 9:47 ` [igt-dev] [Intel-gfx] [PATCH i-g-t 1/3] i915/gem_userptr_blits: Only mlock the memfd once, not the arena Mika Kuoppala
2019-01-16 9:47 ` Mika Kuoppala
2019-01-16 9:58 ` [Intel-gfx] " Chris Wilson
2019-01-16 9:58 ` Chris Wilson
2019-01-16 10:35 ` Mika Kuoppala [this message]
2019-01-16 10:35 ` Mika Kuoppala
2019-01-16 10:46 ` [igt-dev] [Intel-gfx] " Chris Wilson
2019-01-16 10:46 ` Chris Wilson
2019-01-16 10:27 ` [igt-dev] ✓ Fi.CI.BAT: success for series starting with [i-g-t,1/3] " Patchwork
2019-01-16 11:58 ` [igt-dev] ✓ Fi.CI.IGT: " Patchwork
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