Hi Sergey, On Mon, Apr 18, 2016 at 10:04:08AM +0900, Sergey Senozhatsky wrote: > Hello Minchan, > > On (03/30/16 16:12), Minchan Kim wrote: > [..] > > @@ -1835,23 +1827,31 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) > > if (!migrate_zspage(pool, class, &cc)) > > break; > > > > - putback_zspage(pool, class, dst_page); > > + VM_BUG_ON_PAGE(putback_zspage(pool, class, > > + dst_page) == ZS_EMPTY, dst_page); > > can this VM_BUG_ON_PAGE() condition ever be true? I guess it is remained thing after I rebased to catch any mistake. But I'm heavily chainging this part. Please review next version instead of this after a few days. :) > > > } > > /* Stop if we couldn't find slot */ > > if (dst_page == NULL) > > break; > > - putback_zspage(pool, class, dst_page); > > - if (putback_zspage(pool, class, src_page) == ZS_EMPTY) > > + VM_BUG_ON_PAGE(putback_zspage(pool, class, > > + dst_page) == ZS_EMPTY, dst_page); > > hm... this VM_BUG_ON_PAGE(dst_page) is sort of confusing. under what > circumstances it can be true? > > a minor nit, it took me some time (need some coffee I guess) to > correctly parse this macro wrapper > > VM_BUG_ON_PAGE(putback_zspage(pool, class, > dst_page) == ZS_EMPTY, dst_page); > > may be do it like: > fullness = putback_zspage(pool, class, dst_page); > VM_BUG_ON_PAGE(fullness == ZS_EMPTY, dst_page); > > > well, if we want to VM_BUG_ON_PAGE() at all. there haven't been any > problems with compaction, is there any specific reason these macros > were added? > > > > > + if (putback_zspage(pool, class, src_page) == ZS_EMPTY) { > > pool->stats.pages_compacted += class->pages_per_zspage; > > - spin_unlock(&class->lock); > > + spin_unlock(&class->lock); > > + free_zspage(pool, class, src_page); > > do we really need to free_zspage() out of class->lock? > wouldn't something like this > > if (putback_zspage(pool, class, src_page) == ZS_EMPTY) { > pool->stats.pages_compacted += class->pages_per_zspage; > free_zspage(pool, class, src_page); > } > spin_unlock(&class->lock); > > be simpler? The reason I did out of class->lock is deadlock between page_lock and class->lock with upcoming page migration. However, as I said, I'm now heavily changing the part. :) > > besides, free_zspage() now updates class stats out of class lock, > not critical but still. > > -ss > > > + } else { > > + spin_unlock(&class->lock); > > + } > > + > > cond_resched(); > > spin_lock(&class->lock); > > } > > > > if (src_page) > > - putback_zspage(pool, class, src_page); > > + VM_BUG_ON_PAGE(putback_zspage(pool, class, > > + src_page) == ZS_EMPTY, src_page); > > > > spin_unlock(&class->lock); > > } -- 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>