From: Pavel Tatashin <pasha.tatashin@soleen.com>
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, mhocko@suse.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 v5 3/7] mm: Implement new zone specific memblock iterator
Date: Fri, 9 Nov 2018 19:11:16 -0500 [thread overview]
Message-ID: <20181110001116.gtg7vxz2erbrnxc2@xakep.localdomain> (raw)
In-Reply-To: <d511ee6a18da13b9543557db783e6ff3327ca87b.camel@linux.intel.com>
> > > + unsigned long epfn = PFN_DOWN(epa);
> > > + unsigned long spfn = PFN_UP(spa);
> > > +
> > > + /*
> > > + * Verify the end is at least past the start of the zone and
> > > + * that we have at least one PFN to initialize.
> > > + */
> > > + if (zone->zone_start_pfn < epfn && spfn < epfn) {
> > > + /* if we went too far just stop searching */
> > > + if (zone_end_pfn(zone) <= spfn)
> > > + break;
> >
> > Set *idx = U64_MAX here, then break. This way after we are outside this
> > while loop idx is always equals to U64_MAX.
>
> Actually I think what you are asking for is the logic that is outside
> of the while loop we are breaking out of. So if you check at the end of
> the function there is the bit of code with the comment "signal end of
> iteration" where I end up setting *idx to ULLONG_MAX, *out_spfn to
> ULONG_MAX, and *out_epfn to 0.
>
> The general idea I had with the function is that you could use either
> the index or spfn < epfn checks to determine if you keep going or not.
Yes, I meant to remove that *idx = U64_MAX after the loop, it is
confusing to have a loop:
while (*idx != U64_MAX) {
...
}
*idx = U64_MAX;
So, it is better to set idx to U643_MAX inside the loop before the
break.
>
> >
> > > +
> > > + if (out_spfn)
> > > + *out_spfn = max(zone->zone_start_pfn, spfn);
> > > + if (out_epfn)
> > > + *out_epfn = min(zone_end_pfn(zone), epfn);
> >
> > Don't we need to verify after adjustment that out_spfn != out_epfn, so
> > there is at least one PFN to initialize?
>
> We have a few checks that I believe prevent that. Before we get to this
> point we have verified the following:
> zone->zone_start < epfn
> spfn < epfn
>
> The other check that should be helping to prevent that is the break
> statement above that is forcing us to exit if spfn is somehow already
> past the end of the zone, that essentially maps out:
> spfn < zone_end_pfn(zone)
>
> So the only check we don't have is:
> zone->zone_start < zone_end_pfn(zone)
>
> If I am not mistaken that is supposed to be a given is it not? I would
> assume we don't have any zones that are completely empty or inverted
> that would be called here do we?
if (zone_end_pfn(zone) <= spfn) won't break
Equal sign in <= here takes care of the case I was thinking. Yes, logic looks good.
Thank you
Pasha
next prev parent reply other threads:[~2018-11-10 0:11 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 21:19 [mm PATCH v5 0/7] Deferred page init improvements Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 1/7] mm: Use mm_zero_struct_page from SPARC on all 64b architectures Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 2/7] mm: Drop meminit_pfn_in_nid as it is redundant Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 3/7] mm: Implement new zone specific memblock iterator Alexander Duyck
2018-11-09 23:26 ` Pavel Tatashin
2018-11-09 23:58 ` Alexander Duyck
2018-11-10 0:11 ` Pavel Tatashin [this message]
2018-11-05 21:19 ` [mm PATCH v5 4/7] mm: Initialize MAX_ORDER_NR_PAGES at a time instead of doing larger sections Alexander Duyck
2018-11-10 1:02 ` Pavel Tatashin
2018-11-19 18:53 ` Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 5/7] mm: Move hot-plug specific memory init into separate functions and optimize Alexander Duyck
2018-11-10 2:07 ` Pavel Tatashin
2018-11-05 21:19 ` [mm PATCH v5 6/7] mm: Add reserved flag setting to set_page_links Alexander Duyck
2018-11-10 2:11 ` Pavel Tatashin
2018-11-05 21:20 ` [mm PATCH v5 7/7] mm: Use common iterator for deferred_init_pages and deferred_free_pages Alexander Duyck
2018-11-10 4:13 ` Pavel Tatashin
2018-11-12 15:12 ` Alexander Duyck
2018-11-09 21:15 ` [mm PATCH v5 0/7] Deferred page init improvements Pavel Tatashin
2018-11-09 23:14 ` Alexander Duyck
2018-11-10 0:00 ` Pavel Tatashin
2018-11-10 0:46 ` Alexander Duyck
2018-11-10 1:16 ` Pavel Tatashin
2018-11-12 19:10 ` Alexander Duyck
2018-11-12 20:37 ` Pavel Tatashin
2018-11-12 16:25 ` Daniel Jordan
2018-11-14 15:07 ` Michal Hocko
2018-11-14 19:12 ` Pavel Tatashin
2018-11-14 21:35 ` Michal Hocko
2018-11-15 0:50 ` Alexander Duyck
2018-11-15 1:55 ` Mike Rapoport
2018-11-15 19:09 ` Mike Rapoport
2018-11-15 8:10 ` Michal Hocko
2018-11-15 16:02 ` Alexander Duyck
2018-11-15 16:40 ` Michal Hocko
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