On Tue, May 27, 2014 at 08:53:00PM -0700, Hugh Dickins wrote: > On Mon, 26 May 2014, Chen Yucong wrote: > > > For cheap seek, when we scan the region between si->lowset_bit > > and scan_base, if san_base is greater than si->highest_bit, the > > scan operation between si->highest_bit and scan_base is not > > unnecessary. > > > > This patch can be used to avoid scanning invalidated region for > > cheap seek. > > > > Signed-off-by: Chen Yucong <slaoub@xxxxxxxxx> > > I was going to suggest that you are adding a little code to a common > path, in order to optimize a very unlikely case: which does not seem > worthwhile to me. > > But digging a little deeper, I think you have hit upon something more > interesting (though still in no need of your patch): it looks to me > like that is not even a common path, but dead code. > > Shaohua, am I missing something, or does all SWP_SOLIDSTATE "seek is > cheap" now go your si->cluster_info scan_swap_map_try_ssd_cluster() > route? So that the "last_in_cluster < scan_base" loop in the body > of scan_swap_map() is just redundant, and should have been deleted? Sorry for the delay, you are right. SSD case always goes scan_swap_map_try_ssd_cluster, otherwise we just scan from lowest_bit to highest_bit, so the "last_in_cluster < scan_base" loop is dead. Yucong, can you resent a patch to delete it as Hugh suggested? Thanks, Shaohua -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>