On 3/3/23 13:52, Alexander Halbuer wrote:
> On 2/21/23 11:27, Vlastimil Babka wrote:
>> Incidentally, did you observe any improvements by [2] with your test,
>> especially as the batch freeing side also no longer does checking under zone
>> lock?
>>
>> Thanks!
>>
>
> I finally managed to repeat the benchmark to see the effects of
> disabling alloc and free sanity checks by default ("mm, page_alloc:
> reduce page alloc/free sanity checks"; results below).
Thanks for the measurements!
> Average huge page allocation latency drastically reduces by over 90% in
> the single core case. However i can't see any real improvements for the
> free operation.
Ah, I see now why huge page freeing didn't improve. It's because
bulkfree_pcp_prepare() was calling free_page_is_bad(page) thus checking just
the head page. So the tail pages were not actually checked. Just another
detail of how the checking wasn't thorough anyway.
> ---
>
> Measurement results for the batch allocation benchmark for different
> core counts: Internally used functions are alloc_pages_node() for
> allocation (get) and __free_pages() for free (put).
>
> Compared kernel versions are from the mm-unstable branch:
> - Reference version (without the mentioned patch):
> daf4bcbf2b72 ("mm: cma: make kobj_type structure constant")
> - Patched version:
> 60114678f165 ("mm-page_alloc-reduce-page-alloc-free-sanity-checks-fix")
>
> Normale pages
> +-------+------+-------+---------+------+-------+---------+
> | cores | base | patch | diff | base | patch | diff |
> | | get | get | get | put | put | put |
> | | (ns) | (ns) | | (ns) | (ns) | |
> +-------+------+-------+---------+------+-------+---------+
> | 1 | 122 | 118 | (-3.3%) | 118 | 116 | (-1.7%) |
> | 2 | 133 | 130 | (-2.3%) | 130 | 123 | (-5.4%) |
> | 3 | 136 | 132 | (-2.9%) | 175 | 162 | (-7.4%) |
> | 4 | 161 | 149 | (-7.5%) | 241 | 226 | (-6.2%) |
> | 6 | 247 | 228 | (-7.7%) | 366 | 344 | (-6.0%) |
> | 8 | 331 | 304 | (-8.2%) | 484 | 456 | (-5.8%) |
> | 10 | 416 | 390 | (-6.2%) | 615 | 578 | (-6.0%) |
> | 12 | 502 | 472 | (-6.0%) | 727 | 687 | (-5.5%) |
> | 14 | 584 | 552 | (-5.5%) | 862 | 816 | (-5.3%) |
> | 16 | 669 | 632 | (-5.5%) | 967 | 923 | (-4.6%) |
> | 20 | 833 | 787 | (-5.5%) | 1232 | 1164 | (-5.5%) |
> | 24 | 999 | 944 | (-5.5%) | 1462 | 1384 | (-5.3%) |
> +-------+------+-------+---------+------+-------+---------+
>
> Huge Pages
> +-------+------+-------+----------+-------+-------+---------+
> | cores | base | patch | diff | base | patch | diff |
> | | get | get | get | put | put | put |
> | | (ns) | (ns) | | (ns) | (ns) | |
> +-------+------+-------+----------+-------+-------+---------+
> | 1 | 3148 | 177 | (-94.4%) | 2946 | 2872 | (-2.5%) |
> | 2 | 3404 | 596 | (-82.5%) | 3318 | 3306 | (-0.4%) |
> | 3 | 3581 | 950 | (-73.5%) | 3401 | 3358 | (-1.3%) |
> | 4 | 3651 | 1284 | (-64.8%) | 3562 | 3616 | (1.5%) |
> | 6 | 3568 | 1929 | (-45.9%) | 4478 | 4564 | (1.9%) |
> | 8 | 3605 | 2328 | (-35.4%) | 5658 | 5546 | (-2.0%) |
> | 10 | 4093 | 2935 | (-28.3%) | 6758 | 6457 | (-4.5%) |
> | 12 | 4778 | 3540 | (-25.9%) | 7698 | 7565 | (-1.7%) |
> | 14 | 5565 | 4097 | (-26.4%) | 8748 | 8810 | (0.7%) |
> | 16 | 6364 | 4725 | (-25.8%) | 9942 | 10103 | (1.6%) |
> | 20 | 8014 | 5915 | (-26.2%) | 12509 | 12772 | (2.1%) |
> | 24 | 8732 | 7138 | (-18.3%) | 15217 | 15433 | (1.4%) |
> +-------+------+-------+----------+-------+-------+---------+
>
>>>
>>> [1] https://lore.kernel.org/lkml/1d468148-936f-8816-eb71-1662f2d4945b@xxxxxxx/
>>> [2] https://lore.kernel.org/linux-mm/20230216095131.17336-1-vbabka@xxxxxxx/
