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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.1.0 Subject: Re: [PATCH v2 15/16] slab: Allocate frozen pages Content-Language: en-US To: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org Cc: William Kucharski , David Hildenbrand , Mel Gorman References: <20220809171854.3725722-1-willy@infradead.org> <20220809171854.3725722-16-willy@infradead.org> From: Vlastimil Babka In-Reply-To: <20220809171854.3725722-16-willy@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660134673; a=rsa-sha256; cv=none; b=ow0PjmwPug5XC7lCSYuf2dNxava+Dj6cCUSMpd3bu5FLs7rRvjyR4NMURlnHebHbuVUlIp 2HM7s4FmQONkePlAljAeHiFayobqGpWh3yBfkHK+RBfBURfFZZMkJ35nX9u9l+r/bsPr5r qOLqh6ft1eVtbTJJOczzUumM4o6Yh6Q= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="tE/e7Qme"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=Wz0Hk8zM; spf=pass (imf16.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660134673; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IjzcMyggWiy2h/3B1NeX6fwYPAJ5wIr3G+LqU3YS1Vc=; b=HZSCpW2GRdNkiSXDNiDG2p5wZRFV43yGiBcOuJRUvqi2B1TA90rBcY8q9IQoqRpKck79Ch 2klez/e1boLE1jaznqdl+ukvvudYU2t2U23R4EFjjYFlR2ibM/fjTn+zv+teMRdendmZ7r apElmZq3oyX1xIEW0ZYFNfPU+2qL66o= X-Rspamd-Queue-Id: 55B15180047 X-Rspam-User: X-Rspamd-Server: rspam11 Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="tE/e7Qme"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=Wz0Hk8zM; spf=pass (imf16.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Stat-Signature: 3feqj8gte9x14af739nr5iykqd1c1art X-HE-Tag: 1660134673-979499 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: On 8/9/22 19:18, Matthew Wilcox (Oracle) wrote: > Since slab does not use the page refcount, it can allocate and > free frozen pages, saving one atomic operation per free. > > Signed-off-by: Matthew Wilcox (Oracle) > Reviewed-by: William Kucharski AFAICS the problem of has_unmovable_pages() is not addressed: https://lore.kernel.org/all/40d658da-6220-e05e-ba0b-d95c82f6bfb3@redhat.com/ But I don't think it's sustainable approach to enhance the checks there with PageSlab() and then with whatever other user will adopt allocating frozen pages in the future. I guess it would be better to just be able to detect pages on pcplist without false positives. A new page type? Maybe the overhead of managing it would be negligible as we set page->index anyway for migratetype? > --- > mm/slab.c | 23 +++++++++++------------ > 1 file changed, 11 insertions(+), 12 deletions(-) > > diff --git a/mm/slab.c b/mm/slab.c > index 10e96137b44f..e7603d23c6c9 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -1355,23 +1355,23 @@ slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid) > static struct slab *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, > int nodeid) > { > - struct folio *folio; > + struct page *page; > struct slab *slab; > > flags |= cachep->allocflags; > > - folio = (struct folio *) __alloc_pages_node(nodeid, flags, cachep->gfporder); > - if (!folio) { > + page = __alloc_frozen_pages(flags, cachep->gfporder, nodeid, NULL); > + if (!page) { > slab_out_of_memory(cachep, flags, nodeid); > return NULL; > } > > - slab = folio_slab(folio); > + __SetPageSlab(page); > + slab = (struct slab *)page; > > account_slab(slab, cachep->gfporder, cachep, flags); > - __folio_set_slab(folio); > /* Record if ALLOC_NO_WATERMARKS was set when allocating the slab */ > - if (sk_memalloc_socks() && page_is_pfmemalloc(folio_page(folio, 0))) > + if (sk_memalloc_socks() && page_is_pfmemalloc(page)) > slab_set_pfmemalloc(slab); > > return slab; > @@ -1383,18 +1383,17 @@ static struct slab *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, > static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab) > { > int order = cachep->gfporder; > - struct folio *folio = slab_folio(slab); > + struct page *page = (struct page *)slab; > > - BUG_ON(!folio_test_slab(folio)); > __slab_clear_pfmemalloc(slab); > - __folio_clear_slab(folio); > - page_mapcount_reset(folio_page(folio, 0)); > - folio->mapping = NULL; > + __ClearPageSlab(page); > + page_mapcount_reset(page); > + page->mapping = NULL; > > if (current->reclaim_state) > current->reclaim_state->reclaimed_slab += 1 << order; > unaccount_slab(slab, order, cachep); > - __free_pages(folio_page(folio, 0), order); > + free_frozen_pages(page, order); > } > > static void kmem_rcu_free(struct rcu_head *head)