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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id 197sm779868ljf.70.2021.03.25.07.46.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Mar 2021 07:46:13 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 25 Mar 2021 15:46:11 +0100 To: Mel Gorman Cc: Uladzislau Rezki , Matthew Wilcox , Andrew Morton , Chuck Lever , Jesper Dangaard Brouer , Christoph Hellwig , Alexander Duyck , Vlastimil Babka , Ilias Apalodimas , LKML , Linux-Net , Linux-MM , Linux-NFS Subject: Re: [PATCH 0/9 v6] Introduce a bulk order-0 page allocator with two in-tree users Message-ID: <20210325144611.GA2582@pc638.lan> References: <20210325114228.27719-1-mgorman@techsingularity.net> <20210325125001.GW1719932@casper.infradead.org> <20210325132556.GS3697@techsingularity.net> <20210325140657.GA1908@pc638.lan> <20210325142624.GT3697@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210325142624.GT3697@techsingularity.net> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 25, 2021 at 02:26:24PM +0000, Mel Gorman wrote: > On Thu, Mar 25, 2021 at 03:06:57PM +0100, Uladzislau Rezki wrote: > > > On Thu, Mar 25, 2021 at 12:50:01PM +0000, Matthew Wilcox wrote: > > > > On Thu, Mar 25, 2021 at 11:42:19AM +0000, Mel Gorman wrote: > > > > > This series introduces a bulk order-0 page allocator with sunrpc and > > > > > the network page pool being the first users. The implementation is not > > > > > efficient as semantics needed to be ironed out first. If no other semantic > > > > > changes are needed, it can be made more efficient. Despite that, this > > > > > is a performance-related for users that require multiple pages for an > > > > > operation without multiple round-trips to the page allocator. Quoting > > > > > the last patch for the high-speed networking use-case > > > > > > > > > > Kernel XDP stats CPU pps Delta > > > > > Baseline XDP-RX CPU total 3,771,046 n/a > > > > > List XDP-RX CPU total 3,940,242 +4.49% > > > > > Array XDP-RX CPU total 4,249,224 +12.68% > > > > > > > > > > >From the SUNRPC traces of svc_alloc_arg() > > > > > > > > > > Single page: 25.007 us per call over 532,571 calls > > > > > Bulk list: 6.258 us per call over 517,034 calls > > > > > Bulk array: 4.590 us per call over 517,442 calls > > > > > > > > > > Both potential users in this series are corner cases (NFS and high-speed > > > > > networks) so it is unlikely that most users will see any benefit in the > > > > > short term. Other potential other users are batch allocations for page > > > > > cache readahead, fault around and SLUB allocations when high-order pages > > > > > are unavailable. It's unknown how much benefit would be seen by converting > > > > > multiple page allocation calls to a single batch or what difference it may > > > > > make to headline performance. > > > > > > > > We have a third user, vmalloc(), with a 16% perf improvement. I know the > > > > email says 21% but that includes the 5% improvement from switching to > > > > kvmalloc() to allocate area->pages. > > > > > > > > https://lore.kernel.org/linux-mm/20210323133948.GA10046@pc638.lan/ > > > > > > > > > > That's fairly promising. Assuming the bulk allocator gets merged, it would > > > make sense to add vmalloc on top. That's for bringing it to my attention > > > because it's far more relevant than my imaginary potential use cases. > > > > > For the vmalloc we should be able to allocating on a specific NUMA node, > > at least the current interface takes it into account. As far as i see > > the current interface allocate on a current node: > > > > static inline unsigned long > > alloc_pages_bulk_array(gfp_t gfp, unsigned long nr_pages, struct page **page_array) > > { > > return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, NULL, page_array); > > } > > > > Or am i missing something? > > > > No, you're not missing anything. Options would be to add a helper similar > alloc_pages_node or to directly call __alloc_pages_bulk specifying a node > and using GFP_THISNODE. prepare_alloc_pages() should pick the correct > zonelist containing only the required node. > IMHO, a helper something like *_node() would be reasonable. I see that many functions in "mm" have its own variants which explicitly add "_node()" prefix to signal to users that it is a NUMA aware calls. As for __alloc_pages_bulk(), i got it. Thanks! -- Vlad Rezki