From: Michal Hocko <mhocko@kernel.org>
To: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-nvdimm@lists.01.org, davem@davemloft.net,
pavel.tatashin@microsoft.com, mingo@kernel.org,
kirill.shutemov@linux.intel.com, dan.j.williams@intel.com,
dave.jiang@intel.com, rppt@linux.vnet.ibm.com,
willy@infradead.org, vbabka@suse.cz, khalid.aziz@oracle.com,
ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net,
yi.z.zhang@linux.intel.com
Subject: Re: [mm PATCH v6 6/7] mm: Add reserved flag setting to set_page_links
Date: Wed, 5 Dec 2018 21:42:47 +0100 [thread overview]
Message-ID: <20181205204247.GY1286@dhcp22.suse.cz> (raw)
In-Reply-To: <19c9f0fe83a857d5858c386a08ca2ddeba7cf27b.camel@linux.intel.com>
On Wed 05-12-18 09:55:17, Alexander Duyck wrote:
> On Wed, 2018-12-05 at 18:22 +0100, Michal Hocko wrote:
> > On Fri 30-11-18 13:53:18, Alexander Duyck wrote:
> > > Modify the set_page_links function to include the setting of the reserved
> > > flag via a simple AND and OR operation. The motivation for this is the fact
> > > that the existing __set_bit call still seems to have effects on performance
> > > as replacing the call with the AND and OR can reduce initialization time.
> > >
> > > Looking over the assembly code before and after the change the main
> > > difference between the two is that the reserved bit is stored in a value
> > > that is generated outside of the main initialization loop and is then
> > > written with the other flags field values in one write to the page->flags
> > > value. Previously the generated value was written and then then a btsq
> > > instruction was issued.
> > >
> > > On my x86_64 test system with 3TB of persistent memory per node I saw the
> > > persistent memory initialization time on average drop from 23.49s to
> > > 19.12s per node.
> >
> > I have tried to explain why the whole reserved bit doesn't make much
> > sense in this code several times already. You keep ignoring that and
> > that is highly annoying. Especially when you add a tricky code to
> > optimize something that is not really needed.
> >
> > Based on that I am not going to waste my time on other patches in this
> > series to review and give feedback which might be ignored again.
>
> I got your explanation. However Andrew had already applied the patches
> and I had some outstanding issues in them that needed to be addressed.
> So I thought it best to send out this set of patches with those fixes
> before the code in mm became too stale. I am still working on what to
> do about the Reserved bit, and plan to submit it as a follow-up set.
From my experience Andrew can drop patches between different versions of
the patchset. Things can change a lot while they are in mmotm and under
the discussion.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-12-05 20:42 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-30 21:52 [mm PATCH v6 0/7] Deferred page init improvements Alexander Duyck
2018-11-30 21:52 ` [mm PATCH v6 1/7] mm: Use mm_zero_struct_page from SPARC on all 64b architectures Alexander Duyck
2018-11-30 21:52 ` [mm PATCH v6 2/7] mm: Drop meminit_pfn_in_nid as it is redundant Alexander Duyck
2018-11-30 21:53 ` [mm PATCH v6 3/7] mm: Implement new zone specific memblock iterator Alexander Duyck
2018-11-30 21:53 ` [mm PATCH v6 4/7] mm: Initialize MAX_ORDER_NR_PAGES at a time instead of doing larger sections Alexander Duyck
2018-11-30 21:53 ` [mm PATCH v6 5/7] mm: Move hot-plug specific memory init into separate functions and optimize Alexander Duyck
2018-11-30 21:53 ` [mm PATCH v6 6/7] mm: Add reserved flag setting to set_page_links Alexander Duyck
2018-12-05 17:22 ` Michal Hocko
2018-12-05 17:55 ` Alexander Duyck
2018-12-05 20:42 ` Michal Hocko [this message]
2019-03-12 22:07 ` Andrew Morton
2019-03-12 22:50 ` Alexander Duyck
2019-03-13 16:33 ` Andrew Morton
2019-03-13 17:07 ` Alexander Duyck
2018-11-30 21:53 ` [mm PATCH v6 7/7] mm: Use common iterator for deferred_init_pages and deferred_free_pages Alexander Duyck
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