On Wed, Feb 03, 2021 at 04:08:08PM +0530, Prathu Baronia wrote:
> Hey Ira,
> I looked at your below-mentioned patch and I agree that the
> above-mentioned functions also need modification similar to
> clear_user_highpage().
> Would it be okay with you if I send your patch again with a modified
> commit message by adding my data and maintaining your authorship?
> [1]https://lore.kernel.org/lkml/[email protected]/
Sure. I have not changed the patch at all from that version.
Andrew, will this be going through your tree? If not who?
If you take the above patch I can drop it from the series I'm about to submit
to convert btrfs kmaps.
Ira
> Regards,
> Prathu Baronia
>
> On Wed, Feb 3, 2021 at 1:33 AM Ira Weiny <[2][email protected]> wrote:
>
> On Tue, Feb 02, 2021 at 01:12:24PM +0530, Prathu Baronia wrote:
> > In !HIGHMEM cases, specially in 64-bit architectures, we don't need
> temp
> > mapping of pages. Hence, k(map|unmap)_atomic() acts as nothing more
> than
> > multiple barrier() calls, for example for a 2MB hugepage in
> > clear_huge_page() these are called 512 times i.e. to map and unmap
> each
> > subpage that means in total 2048 barrier calls. This called for
> > optimization. Simply getting VADDR from page in the form of
> kmap_local_*
> > APIs does the job for us.? We profiled clear_huge_page() using ftrace
> > and observed an improvement of 62%.
>
> Nice!
>
> >
> > Setup:-
> > Below data has been collected on Qualcomm's SM7250 SoC THP enabled
> > (kernel
> > v4.19.113) with only CPU-0(Cortex-A55) and CPU-7(Cortex-A76) switched
> on
> > and set to max frequency, also DDR set to perf governor.
> >
> > FTRACE Data:-
> >
> > Base data:-
> > Number of iterations: 48
> > Mean of allocation time: 349.5 us
> > std deviation: 74.5 us
> >
> > v1 data:-
> > Number of iterations: 48
> > Mean of allocation time: 131 us
> > std deviation: 32.7 us
> >
> > The following simple userspace experiment to allocate
> > 100MB(BUF_SZ) of pages and writing to it gave us a good insight,
> > we observed an improvement of 42% in allocation and writing timings.
> > -------------------------------------------------------------
> > Test code snippet
> > -------------------------------------------------------------
> >? ? ? ?clock_start();
> >? ? ? ?buf = malloc(BUF_SZ); /* Allocate 100 MB of memory */
> >
> >? ? ? ? ?for(i=0; i < BUF_SZ_PAGES; i++)
> >? ? ? ? ?{
> >? ? ? ? ? ? ? ? ?*((int *)(buf + (i*PAGE_SIZE))) = 1;
> >? ? ? ? ?}
> >? ? ? ?clock_end();
> > -------------------------------------------------------------
> >
> > Malloc test timings for 100MB anon allocation:-
> >
> > Base data:-
> > Number of iterations: 100
> > Mean of allocation time: 31831 us
> > std deviation: 4286 us
> >
> > v1 data:-
> > Number of iterations: 100
> > Mean of allocation time: 18193 us
> > std deviation: 4915 us
> >
> > Reported-by: Chintan Pandya <[3][email protected]>
> > Signed-off-by: Prathu Baronia <[4][email protected]>
>
> Reviewed-by: Ira Weiny <[5][email protected]>
>
> FWIW, I have the same change in a patch in my kmap() changes branch.?
> However,
> my patch also changes clear_highpage(), zero_user_segments(),
> copy_user_highpage(), and copy_highpage().
>
> Would changing those help you as well?
>
> Ira
>
> > ---
> >? include/linux/highmem.h | 4 ++--
> >? 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> > index d2c70d3772a3..444df139b489 100644
> > --- a/include/linux/highmem.h
> > +++ b/include/linux/highmem.h
> > @@ -146,9 +146,9 @@ static inline void
> invalidate_kernel_vmap_range(void *vaddr, int size)
> >? #ifndef clear_user_highpage
> >? static inline void clear_user_highpage(struct page *page, unsigned
> long vaddr)
> >? {
> > -? ? ?void *addr = kmap_atomic(page);
> > +? ? ?void *addr = kmap_local_page(page);
> >? ? ? ?clear_user_page(addr, vaddr, page);
> > -? ? ?kunmap_atomic(addr);
> > +? ? ?kunmap_local(addr);
> >? }
> >? #endif
> >?
> > --
> > 2.17.1
> >
>
> References
>
> Visible links
> 1. https://lore.kernel.org/lkml/[email protected]/
> 2. mailto:[email protected]
> 3. mailto:[email protected]
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