Hi Huang,
On Thu, Dec 17, 2020 at 09:57:28AM +0800, Huang, Ying wrote:
> Hi, Minchan,
>
> In commit 0bcac06f27d7 ("mm, swap: skip swapcache for swapin of
> synchronous device"), swap cache management is skipped for super fast
> device with synchronous IO. That did help performance for these devices
> much at that time. But in commit aae466b0052e ("mm/swap: implement
> workingset detection for anonymous LRU"), swap cache is used to record
> workingset shadow value. So it needs to be operated anyway in swapin in
> common cases. Although lockless operation get_shadow_from_swap_cache()
> is used now, in swap_free() path, swap cache will be locked. So now, is
> it still necessary to skip swap cache logic in do_swap_page() for
> SWP_SYNCHRONOUS_IO? Maybe we can just simplify the logic?
Since we have xarray and better swap management(I believe) since then,
could you try to measure swap-in performance?
If the gain is negligible today, we definitely could drop it.
Thank you.
