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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 8F7CB180028 X-Rspam-User: X-Stat-Signature: exj9bm18cfuofm773ph4g77ynscb7juf X-Rspamd-Server: rspam03 X-HE-Tag: 1710343892-558033 X-HE-Meta: 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 mYe6chj8 OVbR3MIYySLrMzyrZbJ55vveACKDn4QsdvYCnfyhGn16twpF/MGfRXGBSCZ7Pav0ZQnzPlYcTVI5SMgKy4RYYzSEFnbe7KfRlhG4JfNxDK+QmQ+Hhv1YApNs2Eg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 13, 2024 at 3:04=E2=80=AFPM Matthew Wilcox wrote: > > On Wed, Mar 06, 2024 at 10:24:18AM -0800, Suren Baghdasaryan wrote: > > When a non-compound multi-order page is freed, it is possible that a > > speculative reference keeps the page pinned. In this case we free all > > pages except for the first page, which will be freed later by the last > > put_page(). However put_page() ignores the order of the page being free= d, > > treating it as a 0-order page. This creates a memory accounting imbalan= ce > > because the pages freed in __free_pages() do not have their own alloc_t= ag > > and their memory was accounted to the first page. To fix this the first > > page should adjust its allocation size counter when "tail" pages are fr= eed. > > It's not "ignored". It's not available! > > Better wording: > > However the page passed to put_page() is indisinguishable from an > order-0 page, so it cannot do the accounting, just as it cannot free > the subsequent pages. Do the accounting here, where we free the pages. > > (I'm sure further improvements are possible) > > > +static inline void pgalloc_tag_sub_bytes(struct alloc_tag *tag, unsign= ed int order) > > +{ > > + if (mem_alloc_profiling_enabled() && tag) > > + this_cpu_sub(tag->counters->bytes, PAGE_SIZE << order); > > +} > > This is a terribly named function. And it's not even good for what we > want to use it for. > > static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned = int nr) > { > if (mem_alloc_profiling_enabled() && tag) > this_cpu_sub(tag->counters->bytes, PAGE_SIZE * nr); > } > > > +++ b/mm/page_alloc.c > > @@ -4697,12 +4697,21 @@ void __free_pages(struct page *page, unsigned i= nt order) > > { > > /* get PageHead before we drop reference */ > > int head =3D PageHead(page); > > + struct alloc_tag *tag =3D pgalloc_tag_get(page); > > > > if (put_page_testzero(page)) > > free_the_page(page, order); > > else if (!head) > > - while (order-- > 0) > > + while (order-- > 0) { > > free_the_page(page + (1 << order), order); > > + /* > > + * non-compound multi-order page accounts all all= ocations > > + * to the first page (just like compound one), th= erefore > > + * we need to adjust the allocation size of the f= irst > > + * page as its order is ignored when put_page() f= rees it. > > + */ > > + pgalloc_tag_sub_bytes(tag, order); > > - else if (!head > + else if (!head) { > + pgalloc_tag_sub_pages(1 << order - 1); > while (order-- > 0) > free_the_page(page + (1 << order), order); > + } > > It doesn't need a comment, it's obvious what you're doing. All suggestions seem fine to me. I'll adjust the next version accordingly. Thanks for reviewing and the feedback! >