From: "Burakov, Anatoly" <anatoly.burakov@intel.com> To: Alejandro Lucero <alejandro.lucero@netronome.com> Cc: dev <dev@dpdk.org>, dpdk stable <stable@dpdk.org> Subject: Re: [dpdk-dev] [PATCH 17.11] mem: fix memory initialization time Date: Fri, 16 Nov 2018 15:56:16 +0000 Message-ID: <f8fbaac5-c385-f8f4-df3e-6def6a162ed0@intel.com> (raw) In-Reply-To: <CAD+H992sDbY77ajcNaeF5oYsU5=R-mjTiC3VG748GLZX3kxkTQ@mail.gmail.com> On 16-Nov-18 2:42 PM, Alejandro Lucero wrote: > > > On Fri, Nov 16, 2018 at 1:35 PM Burakov, Anatoly > <anatoly.burakov@intel.com <mailto:anatoly.burakov@intel.com>> wrote: > > On 16-Nov-18 12:49 PM, Alejandro Lucero wrote: > > > > > > On Thu, Nov 15, 2018 at 1:16 PM Burakov, Anatoly > > <anatoly.burakov@intel.com <mailto:anatoly.burakov@intel.com> > <mailto:anatoly.burakov@intel.com > <mailto:anatoly.burakov@intel.com>>> wrote: > > > > On 12-Nov-18 11:18 AM, Alejandro Lucero wrote: > > > When using large amount of hugepage based memory, doing > all the > > > hugepages mapping can take quite significant time. > > > > > > The problem is hugepages being initially mmaped to virtual > addresses > > > which will be tried later for the final hugepage mmaping. > This causes > > > the final mapping requiring calling mmap with another hint > > address which > > > can happen several times, depending on the amount of memory to > > mmap, and > > > which each mmmap taking more than a second. > > > > > > This patch changes the hint for the initial hugepage > mmaping using > > > a starting address which will not collide with the final > mmaping. > > > > > > Fixes: 293c0c4b957f ("mem: use address hint for mapping > hugepages") > > > > > > Signed-off-by: Alejandro Lucero > <alejandro.lucero@netronome.com <mailto:alejandro.lucero@netronome.com> > > <mailto:alejandro.lucero@netronome.com > <mailto:alejandro.lucero@netronome.com>>> > > > --- > > > > Hi Alejandro, > > > > I'm not sure i understand the purpose. When final mapping is > performed, > > we reserve new memory area, and map pages into it. (i don't quite > > understand why we unmap the area before mapping pages, but > it's how > > it's > > always been and i didn't change it in the legacy code) > > > > Which addresses are causing the collision? > > > > > > Because the hint for the final mapping is at 4GB address, and the > > hugepages are initially individually mapped starting at low virtual > > addresses, when the memory to map is 4GB or higher, the hugepages > will > > end using that hint address and higher. The more the hugepages to > mmap, > > the more addresses above the hint address are used, and the more > mmaps > > failed for getting the virtual addresses for the final mmap. > > Yes, but i still don't understand what the problem is. > > Before the final mapping, all of the pages get unmapped. They no longer > occupy any VA space at all. Then, we create a VA-area the size of > IOVA-contiguous chunk we have, but then we also unmap *that* (again, no > idea why we actually do that, but that's how it works). So, the final > mapping is performed with the knowledge that there are no pages at > specified addresses, and mapping for specified addresses is performed > when the first mapping has already been unmapped. > > As far as i understand, at no point do we hold addresses for initial > and > final mappings concurrently. So, where does the conflict come in? > > > Are you sure about this? Because I can see calling > unmap_all_hugepage_init happens after the second call to map_all_hugepages. > > Maybe you are looking at the legacy code in a newer version which is not > exactly doing the same steps. Ah yes, you're right - we do remap the pages before we unmap the original mappings. This patch perfect makes sense then. It'd still collide with mappings with --base-virtaddr set to the same address, but it's not going to fail (just be slow again), so it's OK. Acked-by: Anatoly Burakov <anatoly.burakov@intel.com> > > > > > -- > > Thanks, > > Anatoly > > > > > -- > Thanks, > Anatoly > -- Thanks, Anatoly
prev parent reply other threads:[~2018-11-16 15:56 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-11-12 11:18 Alejandro Lucero 2018-11-12 11:26 ` [dpdk-dev] [dpdk-stable] " Eelco Chaudron 2018-11-14 12:45 ` Eelco Chaudron 2018-11-15 13:16 ` [dpdk-dev] " Burakov, Anatoly 2018-11-16 12:49 ` Alejandro Lucero 2018-11-16 13:35 ` Burakov, Anatoly 2018-11-16 14:42 ` Alejandro Lucero 2018-11-16 15:56 ` Burakov, Anatoly [this message]
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