David Laight wrote:
> You could also just not do the copy!
> Although you need (say) asm volatile("\n",:::"memory") to
> stop it all being completely optimised away.
> That might show up a difference in the 'out_of_line' test
> where 15% on top on the data copies is massive - it may be
> that the
From: David Howells
> Sent: 15 September 2023 13:36
>
> David Laight wrote:
>
> > I was thinking of import_iovec() - or whatever its current
> > name is.
>
> That doesn't actually access the buffer described by the iovec[].
>
> > That really needs a single structure that contains the iov_iter
David Laight wrote:
> I was thinking of import_iovec() - or whatever its current
> name is.
That doesn't actually access the buffer described by the iovec[].
> That really needs a single structure that contains the iov_iter
> and the cache[] (which the caller pretty much always allocates
> in t
David Laight wrote:
> Isn't that going to be completely dominated by the cache fills
> from memory?
>
> I'd have thought you'd need to use something with a lot of
> small fragments so that the iteration code dominates the copy.
Okay, if I switch it to using MAP_ANON for the big 256MiB buffer, s
From: David Howells
> Sent: 15 September 2023 12:23
>
> David Laight wrote:
>
> > > > Some measurements can be made using readv() and writev()
> > > > on /dev/zero and /dev/null.
> > >
> > > Forget /dev/null; that doesn't actually engage any iteration code. The
> > > same
> > > for writing to
David Laight wrote:
> > > Some measurements can be made using readv() and writev()
> > > on /dev/zero and /dev/null.
> >
> > Forget /dev/null; that doesn't actually engage any iteration code. The same
> > for writing to /dev/zero. Reading from /dev/zero does its own iteration
> > thing
> > ra
From: David Howells
> Sent: 15 September 2023 11:10
>
> David Laight wrote:
>
> > > Add kunit tests to benchmark 256MiB copies to a UBUF iterator and an IOVEC
> > > iterator. This attaches a userspace VM with a mapped file in it
> > > temporarily to the test thread.
> >
> > Isn't that going to
David Laight wrote:
> > Add kunit tests to benchmark 256MiB copies to a UBUF iterator and an IOVEC
> > iterator. This attaches a userspace VM with a mapped file in it
> > temporarily to the test thread.
>
> Isn't that going to be completely dominated by the cache fills
> from memory?
Yes... b
From: David Howells
> Sent: 14 September 2023 23:15
>
> Add kunit tests to benchmark 256MiB copies to a UBUF iterator and an IOVEC
> iterator. This attaches a userspace VM with a mapped file in it
> temporarily to the test thread.
Isn't that going to be completely dominated by the cache fills
fr
