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[62.201.165.239]) by smtp.gmail.com with ESMTPSA id u3-v6sm898646edo.44.2018.07.20.03.03.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Jul 2018 03:03:27 -0700 (PDT) Received: by techadventures.net (Postfix, from userid 1000) id 2CD751241D6; Fri, 20 Jul 2018 12:03:27 +0200 (CEST) Date: Fri, 20 Jul 2018 12:03:27 +0200 From: Oscar Salvador To: Michal Hocko Cc: akpm@linux-foundation.org, pasha.tatashin@oracle.com, vbabka@suse.cz, aaron.lu@intel.com, iamjoonsoo.kim@lge.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Oscar Salvador Subject: Re: [PATCH v2 3/5] mm/page_alloc: Optimize free_area_init_core Message-ID: <20180720100327.GA19478@techadventures.net> References: <20180719132740.32743-1-osalvador@techadventures.net> <20180719132740.32743-4-osalvador@techadventures.net> <20180719134417.GC7193@dhcp22.suse.cz> <20180719140327.GB10988@techadventures.net> <20180719151555.GH7193@dhcp22.suse.cz> <20180719205235.GA14010@techadventures.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180719205235.GA14010@techadventures.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 19, 2018 at 10:52:35PM +0200, Oscar Salvador wrote: > On Thu, Jul 19, 2018 at 05:15:55PM +0200, Michal Hocko wrote: > > Your changelog doesn't really explain the motivation. Does the change > > help performance? Is this a pure cleanup? > > Hi Michal, > > Sorry to not have explained this better from the very beginning. > > It should help a bit in performance terms as we would be skipping those > condition checks and assignations for zones that do not have any pages. > It is not a huge win, but I think that skipping code we do not really need to run > is worh to have. > > > The function is certainly not an example of beauty. It is more an > > example of changes done on top of older ones without much thinking. But > > I do not see your change would make it so much better. I would consider > > it a much nicer cleanup if it was split into logical units each doing > > one specific thing. > > About the cleanup, I thought that moving that block of code to a separate function > would make the code easier to follow. > If you think that this is still not enough, I can try to split it and see the outcome. I tried to split it innto three logical blocks: - Substract memmap pages - Substract dma reserves - Account kernel pages (nr_kernel_pages and nr_total_pages) Is this something that makes sense to you: diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 10b754fba5fa..1397dcdd4a3c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6237,6 +6237,47 @@ static void pgdat_init_kcompactd(struct pglist_data *pgdat) static void pgdat_init_kcompactd(struct pglist_data *pgdat) {} #endif +static void account_kernel_pages(enum zone_type j, unsigned long freesize, + unsigned long memmap_pages) +{ + if (!is_highmem_idx(j)) + nr_kernel_pages += freesize; + /* Charge for highmem memmap if there are enough kernel pages */ + else if (nr_kernel_pages > memmap_pages * 2) + nr_kernel_pages -= memmap_pages; + nr_all_pages += freesize; +} + +static unsigned long substract_dma_reserves(unsigned long freesize) +{ + /* Account for reserved pages */ + if (freesize > dma_reserve) { + freesize -= dma_reserve; + printk(KERN_DEBUG " %s zone: %lu pages reserved\n", + zone_names[0], dma_reserve); + } + + return freesize; +} + +static unsigned long substract_memmap_pages(unsigned long freesize, unsigned long memmap_pages) +{ + /* + * Adjust freesize so that it accounts for how much memory + * is used by this zone for memmap. This affects the watermark + * and per-cpu initialisations + */ + if (freesize >= memmap_pages) { + freesize -= memmap_pages; + if (memmap_pages) + printk(KERN_DEBUG " %s zone: %lu pages used for memmap\n", + zone_names[j], memmap_pages); + } else + pr_warn(" %s zone: %lu pages exceeds freesize %lu\n", + zone_names[j], memmap_pages, freesize); + return freesize; +} + /* * Set up the zone data structures: * - mark all pages reserved @@ -6267,44 +6308,20 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat) for (j = 0; j < MAX_NR_ZONES; j++) { struct zone *zone = pgdat->node_zones + j; - unsigned long size, freesize, memmap_pages; + unsigned long size = zone->spanned_pages + unsigned long freesize = zone->present_pages; unsigned long zone_start_pfn = zone->zone_start_pfn; - size = zone->spanned_pages; - freesize = zone->present_pages; - - /* - * Adjust freesize so that it accounts for how much memory - * is used by this zone for memmap. This affects the watermark - * and per-cpu initialisations - */ - memmap_pages = calc_memmap_size(size, freesize); - if (!is_highmem_idx(j)) { - if (freesize >= memmap_pages) { - freesize -= memmap_pages; - if (memmap_pages) - printk(KERN_DEBUG - " %s zone: %lu pages used for memmap\n", - zone_names[j], memmap_pages); - } else - pr_warn(" %s zone: %lu pages exceeds freesize %lu\n", - zone_names[j], memmap_pages, freesize); - } + if (size) { + unsigned long memmap_pages = calc_memmap_size(size, freesize); + if (!is_highmem_idx(j)) + freesize = substract_memmap_pages(freesize, memmap_pages); - /* Account for reserved pages */ - if (j == 0 && freesize > dma_reserve) { - freesize -= dma_reserve; - printk(KERN_DEBUG " %s zone: %lu pages reserved\n", - zone_names[0], dma_reserve); + if (j == ZONE_DMA) + freesize = substract_dma_reserves(freesize); + account_kernel_pages(j, freesize, memmap_pages); } - if (!is_highmem_idx(j)) - nr_kernel_pages += freesize; - /* Charge for highmem memmap if there are enough kernel pages */ - else if (nr_kernel_pages > memmap_pages * 2) - nr_kernel_pages -= memmap_pages; - nr_all_pages += freesize; Thanks -- Oscar Salvador SUSE L3