On Mon, Aug 05, 2024 at 12:06:24PM +0800, Alex Shi wrote: > > > On 8/3/24 2:52 AM, Vishal Moola wrote: > > On Mon, Jul 29, 2024 at 07:25:13PM +0800, alexs@xxxxxxxxxx wrote: > >> From: Alex Shi <alexs@xxxxxxxxxx> > > > >> + static_assert(offsetof(struct page, pg) == offsetof(struct zpdesc, zp)) > >> + > >> +ZPDESC_MATCH(flags, flags); > >> +ZPDESC_MATCH(lru, lru); > >> +ZPDESC_MATCH(mapping, mops); > >> +ZPDESC_MATCH(index, next); > >> +ZPDESC_MATCH(index, handle); > >> +ZPDESC_MATCH(private, zspage); > >> +#ifdef CONFIG_MEMCG > >> +ZPDESC_MATCH(memcg_data, memcg_data); > >> +#endif > >> +#undef ZPDESC_MATCH > >> +static_assert(sizeof(struct zpdesc) <= sizeof(struct page)); > >> + > >> +#define zpdesc_page(zp) (_Generic((zp), \ > >> + const struct zpdesc *: (const struct page *)(zp), \ > >> + struct zpdesc *: (struct page *)(zp))) > >> + > >> +#define zpdesc_folio(zp) (_Generic((zp), \ > >> + const struct zpdesc *: (const struct folio *)(zp), \ > >> + struct zpdesc *: (struct folio *)(zp))) > >> + > >> +#define page_zpdesc(p) (_Generic((p), \ > >> + const struct page *: (const struct zpdesc *)(p), \ > >> + struct page *: (struct zpdesc *)(p))) > >> + > >> +#endif > > > > I'm don't think we need both page and folio cast functions for zpdescs. > > Sticking to pages will probably suffice (and be easiest) since all APIs > > zsmalloc cares about are already defined. > > > > We can stick to 1 "middle-man" descriptor for zpdescs since zsmalloc > > uses those pages as space to track zspages and nothing more. We'll likely > > end up completely removing it from zsmalloc once we can allocate > > memdescs on their own: It seems most (if not all) of the "indirect" members > > of zpdesc are used as indicators to the rest of core-mm telling them not to > > mess with that memory. > > Yes, that is also my first attempt to skip folio part, but I found we could got > 6.3% object size reduced on zsmalloc.o file, from 37.2KB to 34.9KB, if we use > folio series lock and folio_get/put functions. That saving come from compound_head > check skipping. > So I wrapped them carefully in zpdesc series functions in zpdesc.h file. > They should be easy replaced when we use memdescs in the future. Could we keep them > a while, or ? IMO, Its alright to keep both pages and folios due to the size reduction. However if we do keep both, it should be clearer that we Want zpdescs to be order-0 pages, and the only reason we have folios is that compound_head() size reduction (and nothing more). I think a comment by the zpdesc_folio() macro will suffice. > Thanks > Alex >
