Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 17 Nov 2023 11:44:10 -0500 | Subject | Re: [linus:master] [iov_iter] c9eec08bac: vm-scalability.throughput -16.9% regression |
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On Fri, 17 Nov 2023 at 11:32, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > The test case seems to be (from the profile) just a simple
Just to clarify: that's the test robot test case. David's test-case is just the simple KUnit test.
> do_iter_readv_writev -> > shmem_file_write_iter -> > generic_perform_write -> > copy_page_from_iter_atomic -> > memcpy_from_iter_mc
.. and more details: this is *not* the actual normal "write()" path, which would copy memory from user space, and that uses our "copy_user()" function etc.
No, the path leading up to this seems to be
worker_thread -> process_one_work -> loop_process_work -> lo_write_simple -> do_iter_write
which is why it uses a regular memcpy (ie it's a kernel buffer due to loop block device).
So the test robot load is kind of odd.
Not that I think that David's KUnit test is necessarily much of a real load either. so...
Linus
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