On Thu, Mar 19, 2015 at 11:39:20AM +0000, Yinghao Xie wrote: > From 159d74b5a8f3d0f07e18ddad74b7025cf17dcc69 Mon Sep 17 00:00:00 2001 > From: Yinghao Xie <[email protected]> > Date: Thu, 19 Mar 2015 19:32:25 +0800 > Subject: [PATCH] mm/zsmalloc.c: count in handle's size when calculating > size_class's pages_per_zspage > > 1. Fix wastage calculation; > 2. Indirect handle introduced extra ZS_HANDLE_SIZE size for each object,it's > transparent > for upper function, but a size_class's total objects will changed: > take the 43rd class which class_size = 32 + 43 * 16 = 720 as example: > 4096 * 1 % 720 = 496 > 4096 * 2 % 720 = 272 > 4096 * 3 % 720 = 48 > 4096 * 4 %720 = 544 > after handle introduced,class_size + ZS_HANDLE_SIZE (4 on 32bit) = 724 > 4096 * 1 % 724 = 476 > 4096 * 2 % 724 = 228 > 4096 * 3 % 724 = 704 > 4096 * 4 % 724 = 456 > Clearly, ZS_HANDLE_SIZE should be considered when calculating > pages_per_zspage;
Zsmalloc adds ZS_SIZE_HANDLE to size user passed before getting size_class so we don't need to change size_class to calculate optimal pages for zspage. > > 3. in get_size_class_index(), min(zs_size_classes - 1, idx) insures a huge > class's > index <= zs_size_classes - 1, so it's no need to check again; Sorry, I don't get it, either. > > Signed-off-by: Yinghao Xie <[email protected]> > --- > mm/zsmalloc.c | 15 ++++++--------- > 1 file changed, 6 insertions(+), 9 deletions(-) > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index 461243e..64c379b 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -760,7 +760,8 @@ out: > * to form a zspage for each size class. This is important > * to reduce wastage due to unusable space left at end of > * each zspage which is given as: > - * wastage = Zp - Zp % size_class > + * wastage = Zp % (class_size + ZS_HANDLE_SIZE) > + * usage = Zp - wastage > * where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ... > * > * For example, for size class of 3/8 * PAGE_SIZE, we should > @@ -773,6 +774,9 @@ static int get_pages_per_zspage(int class_size) > /* zspage order which gives maximum used size per KB */ > int max_usedpc_order = 1; > > + if (class_size > ZS_MAX_ALLOC_SIZE) > + class_size = ZS_MAX_ALLOC_SIZE; > + > for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) { > int zspage_size; > int waste, usedpc; > @@ -1426,11 +1430,6 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t > size) > /* extra space in chunk to keep the handle */ > size += ZS_HANDLE_SIZE; > class = pool->size_class[get_size_class_index(size)]; > - /* In huge class size, we store the handle into first_page->private */ > - if (class->huge) { > - size -= ZS_HANDLE_SIZE; > - class = pool->size_class[get_size_class_index(size)]; > - } > > spin_lock(&class->lock); > first_page = find_get_zspage(class); > @@ -1856,9 +1855,7 @@ struct zs_pool *zs_create_pool(char *name, gfp_t flags) > struct size_class *class; > > size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA; > - if (size > ZS_MAX_ALLOC_SIZE) > - size = ZS_MAX_ALLOC_SIZE; > - pages_per_zspage = get_pages_per_zspage(size); > + pages_per_zspage = get_pages_per_zspage(size + ZS_HANDLE_SIZE); > > /* > * size_class is used for normal zsmalloc operation such > -- > 1.7.9.5 -- 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/
