On Sat, Mar 02, 2024 at 08:27:45AM +1300, Barry Song wrote: > From: Barry Song <v-songbaohua@xxxxxxxx> > > while sg_nents is 1, which is always true for the current kernel > as the only user - zswap is this case, we might have a chance to > remove memcpy, thus improve the performance. > Though sg_nents is 1, its buffer might cross two pages. If those > pages are highmem, we have no cheap way to map them to contiguous > virtual address because kmap doesn't support more than one page > (kmap single higmem page could be still expensive for tlb) and > vmap is expensive. > So we also test and enure page is not highmem in order to safely > use page_to_virt before removing the memcpy. The good news is > that in the most majority of cases, we are lowmem, and we are > always lowmem in those modern and popular hardware. > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Nhat Pham <nphamcs@xxxxxxxxx> > Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> > Tested-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> > --- > -v7: > * fix the problem pointed out by Herbert - flush all pages if dst > is longer than one page. > > crypto/scompress.c | 36 +++++++++++++++++++++++++++++------- > 1 file changed, 29 insertions(+), 7 deletions(-) Patch applied. Thanks. -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
