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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id q24sm2782098ljg.117.2021.02.09.11.49.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Feb 2021 11:49:39 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 9 Feb 2021 20:49:37 +0100 To: Serapheim Dimitropoulos Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, osandov@osandov.com, urezki@gmail.com, serapheim@delphix.com Subject: Re: [PATCH v2] mm/vmalloc: use rb_tree instead of list for vread() lookups Message-ID: <20210209194937.GA2452@pc638.lan> References: <20210209190253.108763-1-serapheim@delphix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210209190253.108763-1-serapheim@delphix.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > vread() has been linearly searching vmap_area_list for looking up > vmalloc areas to read from. These same areas are also tracked by > a rb_tree (vmap_area_root) which offers logarithmic lookup. > > This patch modifies vread() to use the rb_tree structure instead > of the list and the speedup for heavy /proc/kcore readers can > be pretty significant. Below are the wall clock measurements of > a Python application that leverages the drgn debugging library > to read and interpret data read from /proc/kcore. > > Before the patch: > ----- > $ time sudo sdb -e 'dbuf | head 3000 | wc' > (unsigned long)3000 > > real 0m22.446s > user 0m2.321s > sys 0m20.690s > ----- > > With the patch: > ----- > $ time sudo sdb -e 'dbuf | head 3000 | wc' > (unsigned long)3000 > > real 0m2.104s > user 0m2.043s > sys 0m0.921s > ----- > > Signed-off-by: Serapheim Dimitropoulos > --- > Changed in v2: > > - Use __find_vmap_area() for initial lookup but keep iteration via > va->list. > > mm/vmalloc.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 49ab9b6c001d..eb133d000394 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2860,7 +2860,10 @@ long vread(char *buf, char *addr, unsigned long count) > count = -(unsigned long) addr; > > spin_lock(&vmap_area_lock); > - list_for_each_entry(va, &vmap_area_list, list) { > + va = __find_vmap_area((unsigned long)addr); > + if (!va) > + goto finished; > + list_for_each_entry_from(va, &vmap_area_list, list) { > if (!count) > break; > > -- > 2.17.1 > Much better :) Reviewed-by: Uladzislau Rezki (Sony) -- Vlad Rezki