Ops, Sorry for missing Yosry and Nhat. How stupid I am! Here is the first patch on lore: https://lore.kernel.org/all/20240628031138.429622-1-alexs@xxxxxxxxxx/ Sorry for this! Alex On 7/1/24 11:03 AM, Alex Shi wrote: > > > On 6/30/24 9:45 PM, Hyeonggon Yoo wrote: >> On Fri, Jun 28, 2024 at 12:06 PM <alexs@xxxxxxxxxx> wrote: >>> >>> From: Alex Shi <alexs@xxxxxxxxxx> >>> >>> The 1st patch introduces new memory decriptor zpdesc and rename >>> zspage.first_page to zspage.first_zpdesc, no functional change. >>> >>> Originally-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> >>> Signed-off-by: Alex Shi <alexs@xxxxxxxxxx> >>> --- >>> mm/zpdesc.h | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++ >>> mm/zsmalloc.c | 19 ++++++++--------- >>> 2 files changed, 66 insertions(+), 9 deletions(-) >>> create mode 100644 mm/zpdesc.h >> >> Hi Alex, thanks for your effort in pushing this forward! >> >>> diff --git a/mm/zpdesc.h b/mm/zpdesc.h >>> new file mode 100644 >>> index 000000000000..a1ab5ebaa936 >>> --- /dev/null >>> +++ b/mm/zpdesc.h >>> @@ -0,0 +1,56 @@ >>> +/* SPDX-License-Identifier: GPL-2.0 */ >>> +/* zpdesc.h: zswap.zpool memory descriptor >>> + * >>> + * Written by Alex Shi <alexs@xxxxxxxxxx> >>> + * Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> >>> + */ >>> +#ifndef __MM_ZPDESC_H__ >>> +#define __MM_ZPDESC_H__ >>> + >>> +/* >>> + * struct zpdesc - Memory descriptor for zpool memory, now is for zsmalloc >>> + * @flags: Page flags, PG_private: identifies the first component page >>> + * @lru: Indirected used by page migration >> >> maybe Indirected -> Indirectly? > > Hi Yoo, > > Thanks for comments! Yes Indirectly is better. I will update it in next version. > >> >>> + * @next: Next zpdesc in a zspage in zsmalloc zpool >>> + * @handle: For huge zspage in zsmalloc zpool >>> + * @zspage: Pointer to zspage in zsmalloc >>> + * >>> + * This struct overlays struct page for now. Do not modify without a good >>> + * understanding of the issues. >>> + */ >>> +struct zpdesc { >>> + unsigned long flags; >>> + struct list_head lru; >>> + unsigned long _zp_pad_1; >> >> for understanding, I think it'd be better to replace _zp_pad_1 with movable ops, >> because mops reuses this 'mapping' field. > > Right, 'mops' looks a bit more clear. > >> >>> + union { >>> + /* Next zpdescs in a zspage in zsmalloc zpool */ >>> + struct zpdesc *next; >>> + /* For huge zspage in zsmalloc zpool */ >>> + unsigned long handle; >>> + }; >>> + struct zspage *zspage; >> >> There was a discussion with Yosry on including memcg_data on zpdesc >> even if it's not used at the moment. >> >> Maybe you can look at: >> https://lore.kernel.org/linux-mm/CAB=+i9Quz9iP2-Lq=oQfKVVnzPDtOaKMm=hUPbnRg5hRxH+qaA@xxxxxxxxxxxxxx/ > > Thanks for notice. > The memcg_data isn't used for zpdesc. And I have a bit confusion since Yosry said: "I think to drop memcg_data we need to enlighten the code that ...". So we actually don't need to have this unused member, is this right, Yosry? > >> >>> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c >>> index fec1a39e5bbe..67bb80b7413a 100644 >>> --- a/mm/zsmalloc.c >>> +++ b/mm/zsmalloc.c >>> @@ -13,17 +13,17 @@ >>> >>> /* >>> * Following is how we use various fields and flags of underlying >>> - * struct page(s) to form a zspage. >>> + * struct zpdesc(page) to form a zspage. >>> * >>> - * Usage of struct page fields: >>> - * page->private: points to zspage >>> - * page->index: links together all component pages of a zspage >>> + * Usage of struct zpdesc fields: >>> + * zpdesc->zspage: points to zspage >>> + * zpdesc->next: links together all component pages of a zspage >>> * For the huge page, this is always 0, so we use this field >>> * to store handle. >>> * page->page_type: PG_zsmalloc, lower 16 bit locate the first object >>> * offset in a subpage of a zspage >>> * >>> - * Usage of struct page flags: >>> + * Usage of struct zpdesc(page) flags: >>> * PG_private: identifies the first component page >>> * PG_owner_priv_1: identifies the huge component page >> >> the comment for PG_owner_priv_1 can safely be removed as it's not used >> after commit a41ec880aa7b ("zsmalloc: move huge compressed obj from >> page to zspage") > > Right, thanks for info! > >> >>> @@ -948,7 +949,7 @@ static void create_page_chain(struct size_class *class, struct zspage *zspage, >>> set_page_private(page, (unsigned long)zspage); >>> page->index = 0; >>> if (i == 0) { >>> - zspage->first_page = page; >>> + zspage->first_zpdesc = page_zpdesc(page); >>> SetPagePrivate(page); >>> if (unlikely(class->objs_per_zspage == 1 && >>> class->pages_per_zspage == 1)) >>> @@ -1325,7 +1326,7 @@ static unsigned long obj_malloc(struct zs_pool *pool, >>> link->handle = handle; >>> else >>> /* record handle to page->index */ >>> - zspage->first_page->index = handle; >>> + zspage->first_zpdesc->handle = handle; >> >> FYI this line seems to conflict with >> bcc6116e39f512 ("mm/zsmalloc: move record_obj() into obj_malloc()") >> on mm-unstable. > > yes, a new commit made this conflict. will update this in next version. > > Thanks > Alex >> >> Best, >> Hyeonggon
