From: Michal Hocko <mhocko@suse.com>
To: Ben Widawsky <ben.widawsky@intel.com>
Cc: Feng Tang <feng.tang@intel.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
David Rientjes <rientjes@google.com>,
Mel Gorman <mgorman@techsingularity.net>,
Mike Kravetz <mike.kravetz@oracle.com>,
Randy Dunlap <rdunlap@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>,
"Hansen, Dave" <dave.hansen@intel.com>,
Andi leen <ak@linux.intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>
Subject: Re: [PATCH v3 RFC 14/14] mm: speedup page alloc for MPOL_PREFERRED_MANY by adding a NO_SLOWPATH gfp bit
Date: Wed, 3 Mar 2021 18:14:30 +0100 [thread overview]
Message-ID: <YD/D9hckPOA+41+D@dhcp22.suse.cz> (raw)
In-Reply-To: <20210303163141.v5wu2sfo2zj2qqsw@intel.com>
On Wed 03-03-21 08:31:41, Ben Widawsky wrote:
> On 21-03-03 14:59:35, Michal Hocko wrote:
> > On Wed 03-03-21 21:46:44, Feng Tang wrote:
> > > On Wed, Mar 03, 2021 at 09:18:32PM +0800, Tang, Feng wrote:
> > > > On Wed, Mar 03, 2021 at 01:32:11PM +0100, Michal Hocko wrote:
> > > > > On Wed 03-03-21 20:18:33, Feng Tang wrote:
> > [...]
> > > > > > One thing I tried which can fix the slowness is:
> > > > > >
> > > > > > + gfp_mask &= ~(__GFP_DIRECT_RECLAIM | __GFP_KSWAPD_RECLAIM);
> > > > > >
> > > > > > which explicitly clears the 2 kinds of reclaim. And I thought it's too
> > > > > > hacky and didn't mention it in the commit log.
> > > > >
> > > > > Clearing __GFP_DIRECT_RECLAIM would be the right way to achieve
> > > > > GFP_NOWAIT semantic. Why would you want to exclude kswapd as well?
> > > >
> > > > When I tried gfp_mask &= ~__GFP_DIRECT_RECLAIM, the slowness couldn't
> > > > be fixed.
> > >
> > > I just double checked by rerun the test, 'gfp_mask &= ~__GFP_DIRECT_RECLAIM'
> > > can also accelerate the allocation much! though is still a little slower than
> > > this patch. Seems I've messed some of the tries, and sorry for the confusion!
> > >
> > > Could this be used as the solution? or the adding another fallback_nodemask way?
> > > but the latter will change the current API quite a bit.
> >
> > I haven't got to the whole series yet. The real question is whether the
> > first attempt to enforce the preferred mask is a general win. I would
> > argue that it resembles the existing single node preferred memory policy
> > because that one doesn't push heavily on the preferred node either. So
> > dropping just the direct reclaim mode makes some sense to me.
> >
> > IIRC this is something I was recommending in an early proposal of the
> > feature.
>
> My assumption [FWIW] is that the usecases we've outlined for multi-preferred
> would want more heavy pushing on the preference mask. However, maybe the uapi
> could dictate how hard to try/not try.
What does that mean and what is the expectation from the kernel to be
more or less cast in stone?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-03-03 19:29 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-03 10:20 [PATCH v3 00/14] Introduced multi-preference mempolicy Feng Tang
2021-03-03 10:20 ` [PATCH v3 01/14] mm/mempolicy: Add comment for missing LOCAL Feng Tang
2021-03-10 6:27 ` Feng Tang
2021-03-03 10:20 ` [PATCH v3 02/14] mm/mempolicy: convert single preferred_node to full nodemask Feng Tang
2021-03-03 10:20 ` [PATCH v3 03/14] mm/mempolicy: Add MPOL_PREFERRED_MANY for multiple preferred nodes Feng Tang
2021-03-03 10:20 ` [PATCH v3 04/14] mm/mempolicy: allow preferred code to take a nodemask Feng Tang
2021-03-03 10:20 ` [PATCH v3 05/14] mm/mempolicy: refactor rebind code for PREFERRED_MANY Feng Tang
2021-03-03 10:20 ` [PATCH v3 06/14] mm/mempolicy: kill v.preferred_nodes Feng Tang
2021-03-03 10:20 ` [PATCH v3 07/14] mm/mempolicy: handle MPOL_PREFERRED_MANY like BIND Feng Tang
2021-03-03 10:20 ` [PATCH v3 08/14] mm/mempolicy: Create a page allocator for policy Feng Tang
2021-03-03 10:20 ` [PATCH v3 09/14] mm/mempolicy: Thread allocation for many preferred Feng Tang
2021-03-03 10:20 ` [PATCH v3 10/14] mm/mempolicy: VMA " Feng Tang
2021-03-03 10:20 ` [PATCH v3 11/14] mm/mempolicy: huge-page " Feng Tang
2021-03-03 10:20 ` [PATCH v3 12/14] mm/mempolicy: Advertise new MPOL_PREFERRED_MANY Feng Tang
2021-03-03 10:20 ` [PATCH v3 13/14] mem/mempolicy: unify mpol_new_preferred() and mpol_new_preferred_many() Feng Tang
2021-03-03 10:20 ` [PATCH v3 RFC 14/14] mm: speedup page alloc for MPOL_PREFERRED_MANY by adding a NO_SLOWPATH gfp bit Feng Tang
2021-03-03 11:39 ` Michal Hocko
2021-03-03 12:07 ` Feng Tang
2021-03-03 12:18 ` Feng Tang
2021-03-03 12:32 ` Michal Hocko
2021-03-03 13:18 ` Feng Tang
2021-03-03 13:46 ` Feng Tang
2021-03-03 13:59 ` Michal Hocko
2021-03-03 16:31 ` Ben Widawsky
2021-03-03 16:48 ` Dave Hansen
2021-03-10 5:19 ` Feng Tang
2021-03-10 9:44 ` Michal Hocko
2021-03-10 11:49 ` Feng Tang
2021-03-03 17:14 ` Michal Hocko [this message]
2021-03-03 17:22 ` Ben Widawsky
2021-03-04 8:14 ` Feng Tang
2021-03-04 12:59 ` Michal Hocko
2021-03-05 2:21 ` Feng Tang
2021-03-04 12:57 ` Michal Hocko
2021-03-03 13:53 ` Michal Hocko
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