On Mon, Jul 06, 2015 at 09:17:49PM +0900, Sergey Senozhatsky wrote: > Compaction returns back to zram the number of migrated objects, > which is quite uninformative -- we have objects of different > sizes so user space cannot obtain any valuable data from that > number. Change compaction to operate in terms of pages and > return back to compaction issuer the number of pages that > were freed during compaction. So from now on `num_compacted' > column in zram<id>/mm_stat represents more meaningful value: > the number of freed (compacted) pages.
Fair enough. The main reason I introduced num_migrated is to investigate the effieciency of compaction. ie, num_freed / num_migrated. However, I didn't put num_freed at that time so I can't get my goal with only num_migrated. We could put new knob num_compacted as well as num_migrated but I don't think we need it now. Zram's compaction would be much efficient compared to VM's compaction because we don't have any non-movable objects in zspages and we can account exact number of free slots. So, I want to change name from num_migrated to num_compacted and maintain only it which is more useful for admin, you said. It's not far since we introduced num_migrated so I don't think change name wouldn't be a big problem for userspace,(I hope). > > Return first_page's fullness_group from putback_zspage(), > so we now for sure know that putback_zspage() has issued > free_zspage() and we must update compaction stats. > > Update documentation. > > Signed-off-by: Sergey Senozhatsky <[email protected]> > --- > Documentation/blockdev/zram.txt | 3 ++- > mm/zsmalloc.c | 27 +++++++++++++++++---------- > 2 files changed, 19 insertions(+), 11 deletions(-) > > diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt > index c4de576..71f4744 100644 > --- a/Documentation/blockdev/zram.txt > +++ b/Documentation/blockdev/zram.txt > @@ -144,7 +144,8 @@ mem_used_max RW the maximum amount memory zram > have consumed to > store compressed data > mem_limit RW the maximum amount of memory ZRAM can use to store > the compressed data > -num_migrated RO the number of objects migrated migrated by compaction > +num_migrated RO the number of pages freed during compaction > + (available only via zram<id>/mm_stat node) > compact WO trigger memory compaction > > WARNING > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index e0f508a..a761733 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -245,7 +245,7 @@ struct zs_pool { > /* Allocation flags used when growing pool */ > gfp_t flags; > atomic_long_t pages_allocated; > - /* How many objects were migrated */ > + /* How many pages were migrated (freed) */ > unsigned long num_migrated; > > #ifdef CONFIG_ZSMALLOC_STAT > @@ -1596,8 +1596,6 @@ struct zs_compact_control { > /* Starting object index within @s_page which used for live object > * in the subpage. */ > int index; > - /* How many of objects were migrated */ > - int nr_migrated; > }; > > static int migrate_zspage(struct zs_pool *pool, struct size_class *class, > @@ -1634,7 +1632,6 @@ static int migrate_zspage(struct zs_pool *pool, struct > size_class *class, > record_obj(handle, free_obj); > unpin_tag(handle); > obj_free(pool, class, used_obj); > - cc->nr_migrated++; > } > > /* Remember last position in this iteration */ > @@ -1660,8 +1657,17 @@ static struct page *isolate_target_page(struct > size_class *class) > return page; > } > > -static void putback_zspage(struct zs_pool *pool, struct size_class *class, > - struct page *first_page) > +/* > + * putback_zspage - add @first_page into right class's fullness list > + * @pool: target pool > + * @class: destination class > + * @first_page: target page > + * > + * Return @fist_page's fullness_group > + */ > +static enum fullness_group putback_zspage(struct zs_pool *pool, > + struct size_class *class, > + struct page *first_page) > { > enum fullness_group fullness; > > @@ -1679,6 +1685,8 @@ static void putback_zspage(struct zs_pool *pool, struct > size_class *class, > > free_zspage(first_page); > } > + > + return fullness; > } > > static struct page *isolate_source_page(struct size_class *class) > @@ -1720,7 +1728,6 @@ static void __zs_compact(struct zs_pool *pool, struct > size_class *class) > struct page *src_page; > struct page *dst_page = NULL; > > - cc.nr_migrated = 0; > spin_lock(&class->lock); > while ((src_page = isolate_source_page(class))) { > > @@ -1749,7 +1756,9 @@ static void __zs_compact(struct zs_pool *pool, struct > size_class *class) > break; > > putback_zspage(pool, class, dst_page); > - putback_zspage(pool, class, src_page); > + if (putback_zspage(pool, class, src_page) == ZS_EMPTY) > + pool->num_migrated += > + get_pages_per_zspage(class->size); > spin_unlock(&class->lock); > cond_resched(); > spin_lock(&class->lock); > @@ -1758,8 +1767,6 @@ static void __zs_compact(struct zs_pool *pool, struct > size_class *class) > if (src_page) > putback_zspage(pool, class, src_page); > > - pool->num_migrated += cc.nr_migrated; > - > spin_unlock(&class->lock); > } > > -- > 2.5.0.rc0.3.g912bd49 > -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
