On Wed, Jan 13, 2021 at 11:12 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Wed, Jan 13, 2021 at 11:08:56AM +0800, huang ying wrote: > > On Wed, Jan 13, 2021 at 10:47 AM Linus Torvalds > > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Tue, Jan 12, 2021 at 6:43 PM Huang Ying <ying.huang@xxxxxxxxx> wrote: > > > > > > > > So in this patch, at the end of wp_page_copy(), the old unused swap > > > > cache page will be tried to be freed. > > > > > > I'd much rather free it later when needed, rather than when you're in > > > a COW section. > > > > Unused swap cache isn't unused file cache. Nobody can reuse them > > directly before freeing them firstly. It will make COW a little > > faster via keeping them. But I think the overhead to free them isn't > > high. While keeping them in system will confuse users (users will > > expect file cache to use free memory, but not expect unused swap cache > > to use much free memory), make the swap space more fragmented, and add > > system overall overhead (scanning LRU list, etc.). > > Couldn't we just move it to the tail of the LRU list so it's reclaimed > first? Or is locking going to be a problem here? Yes. That's a way to reduce the disturbance to the page reclaiming. For LRU lock contention, is it sufficient to use another pagevec? Best Regards, Huang, Ying
