From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941245AbdAGJ2H (ORCPT ); Sat, 7 Jan 2017 04:28:07 -0500 Received: from mx2.suse.de ([195.135.220.15]:33375 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932214AbdAGJ1v (ORCPT ); Sat, 7 Jan 2017 04:27:51 -0500 Date: Sat, 7 Jan 2017 10:27:48 +0100 From: Michal Hocko To: Eric Dumazet Cc: Tom Herbert , linux-mm@kvack.org, LKML , edumazet@google.com Subject: Re: weird allocation pattern in alloc_ila_locks Message-ID: <20170107092746.GC5047@dhcp22.suse.cz> References: <20170106095115.GG5556@dhcp22.suse.cz> <20170106100433.GH5556@dhcp22.suse.cz> <20170106121642.GJ5556@dhcp22.suse.cz> <1483740889.9712.44.camel@edumazet-glaptop3.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1483740889.9712.44.camel@edumazet-glaptop3.roam.corp.google.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 06-01-17 14:14:49, Eric Dumazet wrote: > On Fri, 2017-01-06 at 13:16 +0100, Michal Hocko wrote: > > I was thinking about the rhashtable which was the source of the c&p and > > it can be simplified as well. > > --- > > From 555543604f5f020284ea85d928d52f6a55fde7ca Mon Sep 17 00:00:00 2001 > > From: Michal Hocko > > Date: Fri, 6 Jan 2017 13:12:31 +0100 > > Subject: [PATCH] rhashtable: simplify a strange allocation pattern > > > > alloc_bucket_locks allocation pattern is quite unusual. We are > > preferring vmalloc when CONFIG_NUMA is enabled which doesn't make much > > sense because there is no special NUMA locality handled in that code > > path. Let's just simplify the code and use kvmalloc helper, which is a > > transparent way to use kmalloc with vmalloc fallback, if the caller > > is allowed to block and use the flag otherwise. > > > > Signed-off-by: Michal Hocko > > --- > > lib/rhashtable.c | 13 +++---------- > > 1 file changed, 3 insertions(+), 10 deletions(-) > > > > diff --git a/lib/rhashtable.c b/lib/rhashtable.c > > index 32d0ad058380..4d3886b6ab7d 100644 > > --- a/lib/rhashtable.c > > +++ b/lib/rhashtable.c > > @@ -77,16 +77,9 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl, > > size = min_t(unsigned int, size, tbl->size >> 1); > > > > if (sizeof(spinlock_t) != 0) { > > - tbl->locks = NULL; > > -#ifdef CONFIG_NUMA > > - if (size * sizeof(spinlock_t) > PAGE_SIZE && > > - gfp == GFP_KERNEL) > > - tbl->locks = vmalloc(size * sizeof(spinlock_t)); > > -#endif > > - if (gfp != GFP_KERNEL) > > - gfp |= __GFP_NOWARN | __GFP_NORETRY; > > - > > - if (!tbl->locks) > > + if (gfpflags_allow_blocking(gfp_)) > > + tbl->locks = kvmalloc(size * sizeof(spinlock_t), gfp); > > + else > > tbl->locks = kmalloc_array(size, sizeof(spinlock_t), > > > I believe the intent was to get NUMA spreading, a bit like what we have > in alloc_large_system_hash() when hashdist == HASHDIST_DEFAULT Hmm, I am not sure this works as expected then. Because it is more likely that all pages backing the vmallocked area will come from the local node than spread around more nodes. Or did I miss your point? -- Michal Hocko SUSE Labs