From: Michael Ellerman <patch-notifications@ellerman•id.au>
To: Nicholas Piggin <npiggin@gmail•com>, linuxppc-dev@lists•ozlabs.org
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux•vnet.ibm.com>,
Nicholas Piggin <npiggin@gmail•com>
Subject: Re: [v2,5/7] powerpc/64s/radix: Optimize flush_tlb_range
Date: Tue, 14 Nov 2017 22:12:16 +1100 (AEDT) [thread overview]
Message-ID: <3yblG84gfXz9t16@ozlabs.org> (raw)
In-Reply-To: <20171107075309.20500-6-npiggin@gmail.com>
On Tue, 2017-11-07 at 07:53:07 UTC, Nicholas Piggin wrote:
> Currently for radix, flush_tlb_range flushes the entire PID, because
> the Linux mm code does not tell us about page size here for THP vs
> regular pages. This is quite sub-optimal for small mremap / mprotect
> / change_protection.
>
> So implement va range flushes with two flush passes, one for each
> page size (regular and THP). The second flush has an order of matnitude
> fewer tlbie instructions than the first, so it is a relatively small
> additional cost.
>
> There is still room for improvement here with some changes to generic
> APIs, particularly if there are mostly THP pages to be invalidated,
> the small page flushes could be reduced.
>
> Time to mprotect 1 page of memory (after mmap, touch):
> vanilla 2.9us 1.8us
> patched 1.2us 1.6us
>
> Time to mprotect 30 pages of memory (after mmap, touch):
> vanilla 8.2us 7.2us
> patched 6.9us 17.9us
>
> Time to mprotect 34 pages of memory (after mmap, touch):
> vanilla 9.1us 8.0us
> patched 9.0us 8.0us
>
> 34 pages is the point at which the invalidation switches from va
> to entire PID, which tlbie can do in a single instruction. This is
> why in the case of 30 pages, the new code runs slower for this test.
> This is a deliberate tradeoff already present in the unmap and THP
> promotion code, the idea is that the benefit from avoiding flushing
> entire TLB for this PID on all threads in the system.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail•com>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/cbf09c837720f72f5e63ab7a2d331e
cheers
next prev parent reply other threads:[~2017-11-14 11:12 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-07 7:53 [PATCH v2 0/7] powerpc/64s/radix TLB flush fixes and performance improvements Nicholas Piggin
2017-11-07 7:53 ` [PATCH v2 1/7] powerpc/64s/radix: tlbie improve preempt handling Nicholas Piggin
2017-11-07 7:53 ` [PATCH v2 2/7] powerpc/64s/radix: Fix process table entry cache invalidation Nicholas Piggin
2017-11-07 7:53 ` [PATCH v2 3/7] powerpc/64s/radix: optimize TLB range flush barriers Nicholas Piggin
2017-11-14 11:12 ` [v2,3/7] " Michael Ellerman
2017-11-07 7:53 ` [PATCH v2 4/7] powerpc/64s/radix: Implement _tlbie(l)_va_range flush functions Nicholas Piggin
2017-11-14 11:12 ` [v2, " Michael Ellerman
2017-11-07 7:53 ` [PATCH v2 5/7] powerpc/64s/radix: Optimize flush_tlb_range Nicholas Piggin
2017-11-14 11:12 ` Michael Ellerman [this message]
2017-11-07 7:53 ` [PATCH v2 6/7] powerpc/64s/radix: Introduce local single page ceiling for TLB range flush Nicholas Piggin
2017-11-14 11:12 ` [v2, " Michael Ellerman
2017-11-07 7:53 ` [PATCH v2 7/7] powerpc/64s/radix: Improve TLB flushing for page table freeing Nicholas Piggin
2017-11-14 11:12 ` [v2, " Michael Ellerman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3yblG84gfXz9t16@ozlabs.org \
--to=patch-notifications@ellerman$(echo .)id.au \
--cc=aneesh.kumar@linux$(echo .)vnet.ibm.com \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=npiggin@gmail$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox