From: Michael Ellerman <mpe@ellerman•id.au>
To: "Michal Suchánek" <msuchanek@suse•de>
Cc: linuxppc-dev@ozlabs•org, npiggin@gmail•com
Subject: Re: [PATCH 4/4] powerpc/64s: Support shrinking the SLB for debugging
Date: Sat, 19 Jan 2019 21:27:21 +1100 [thread overview]
Message-ID: <87won12b92.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20190119011314.45cb9864@naga>
Michal Suchánek <msuchanek@suse•de> writes:
> On Thu, 17 Jan 2019 23:13:28 +1100
> Michael Ellerman <mpe@ellerman•id.au> wrote:
>
>> On machines with 1TB segments and a 32-entry SLB it's quite hard to
>> cause sufficient SLB pressure to trigger bugs caused due to badly
>> timed SLB faults.
>>
>> We have seen this in the past and a few years ago added the
>> disable_1tb_segments command line option to force the use of 256MB
>> segments. However even this allows some bugs to slip through testing
>> if the SLB entry in question was recently accessed.
>>
>> So add a new command line parameter for debugging which shrinks the
>> SLB to the minimum size we can support. Currently that size is 3, two
>> bolted SLBs and 1 for dynamic use. This creates the maximal SLB
>
> Doesn't this violate the power of 2 requirement stated in 2/4?
Yes. Good point. This was originally a hack patch in my tree, back when
SLB_NUM_BOLTED was 3 and before Nick even added the slb_used_bitmap, so
back then it was a power of 2 but it also didn't matter :)
I think I'll rework the slb_full_bitmap patch anyway and remove the
power of 2 requirement, so then this patch will be OK.
Thanks for the review!
cheers
next prev parent reply other threads:[~2019-01-19 10:28 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-17 12:13 [PATCH 1/4] powerpc/64s: Always set mmu_slb_size using slb_set_size() Michael Ellerman
2019-01-17 12:13 ` [PATCH 2/4] powerpc/64s: Add slb_full_bitmap rather than hard-coding U32_MAX Michael Ellerman
2019-01-17 16:30 ` Segher Boessenkool
2019-01-18 12:28 ` Michael Ellerman
2019-01-18 23:12 ` Segher Boessenkool
2019-01-23 9:02 ` Aneesh Kumar K.V
2019-01-17 12:13 ` [PATCH 3/4] powerpc/64s: Move SLB init into hash_utils_64.c Michael Ellerman
2019-01-23 9:04 ` Aneesh Kumar K.V
2019-01-17 12:13 ` [PATCH 4/4] powerpc/64s: Support shrinking the SLB for debugging Michael Ellerman
2019-01-19 0:13 ` Michal Suchánek
2019-01-19 10:27 ` Michael Ellerman [this message]
2019-01-23 8:40 ` Nicholas Piggin
2019-01-23 9:10 ` Aneesh Kumar K.V
2019-01-23 8:59 ` [PATCH 1/4] powerpc/64s: Always set mmu_slb_size using slb_set_size() Aneesh Kumar K.V
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