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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id i12sm1199593lfv.220.2021.03.22.15.36.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 15:36:21 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 22 Mar 2021 23:36:19 +0100 To: "Matthew Wilcox (Oracle)" Cc: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Uladzislau Rezki , Nicholas Piggin Subject: Re: [PATCH 2/2] mm/vmalloc: Use kvmalloc to allocate the table of pages Message-ID: <20210322223619.GA56503@pc638.lan> References: <20210322193820.2140045-1-willy@infradead.org> <20210322193820.2140045-2-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210322193820.2140045-2-willy@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 22, 2021 at 07:38:20PM +0000, Matthew Wilcox (Oracle) wrote: > If we're trying to allocate 4MB of memory, the table will be 8KiB in size > (1024 pointers * 8 bytes per pointer), which can usually be satisfied > by a kmalloc (which is significantly faster). Instead of changing this > open-coded implementation, just use kvmalloc(). > > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/vmalloc.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 96444d64129a..32b640a84250 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2802,13 +2802,8 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, > gfp_mask |= __GFP_HIGHMEM; > > /* Please note that the recursion is strictly bounded. */ > - if (array_size > PAGE_SIZE) { > - pages = __vmalloc_node(array_size, 1, nested_gfp, node, > + pages = kvmalloc_node_caller(array_size, nested_gfp, node, > area->caller); > - } else { > - pages = kmalloc_node(array_size, nested_gfp, node); > - } > - > if (!pages) { > free_vm_area(area); > return NULL; > -- > 2.30.2 Makes sense to me. Though i expected a bigger difference: # patch single CPU, 4MB allocation, loops: 1000000 avg: 85293854 usec # default single CPU, 4MB allocation, loops: 1000000 avg: 89275857 usec One question. Should we care much about fragmentation? I mean with the patch, allocations > 2MB will do request to SLAB bigger then PAGE_SIZE. Thanks! -- Vlad Rezki