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Re: [PATCH v11 44/60] PCI: Add alt_size ressource allocation support

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On Thu, Apr 7, 2016 at 5:56 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> I'm not excited about the whole "alternate aligment".
>
> Maybe the kernel should just accept the smaller alignment. If the
> minimum alignment we use is bigger than necessary, then we're just
> wrong about it, and perhaps we should just use the smaller alignment
> that the bios used.

Look like I did not make it clearly in this change log.

Current kernel code sizing is searching smallest alignment, so call it
min_align scheme.

Some bios is using different way: It use smallest size instead, but it
could have bigger alignment
than min_align, so I call it alt_size scheme.

PROs for min_align: it can be used to calculate upper parent bridges
easily and safely.
CONs for min_align: it could generate more bigger required size.

PROs for alt_size: it try to search smaller size, esp for under 4G mmio space.
CONs for alt_size: it could have much bigger alignment, and need to
calculate the upper
bridge alt_size carefully. We end it up with try out to search the
upper bridge alt_size.

Current min_align code still have other problem: it can not handle block that
size is bigger than alignment, and it would generate wrong/too big align/size.

In the patch set, We
1. fix the min_align scheme to use try out way to find right min_align even
block size if bigger than block alignment.
2. add alt_size scheme, it will search alt_size/alt_align, that have
smaller size
   a. compare that with min_align/min_size, if alt_size is not smaller
than min_size
       just dump alt_size. otherwise record alt_size.
   b. later if we fail to get allocation with min_align, we retry alt_size.

So we still keep the old way as usual, and only handle some extra
corner case like
1. BIOS use small size and big align allocation, and in kernel we are doing pci
device remove or rescan.
2. We have couple layers of bridges that min_align scheme is wasting space.
and we have tight mmio under 4G.

Please let me know if I describe it clearly this time, otherwise I
would extract sample output
from patches and post here.

Thanks

Yinghai

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[PATCH v11 00/60] PCI: Resource allocation cleanup for v4.7 Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 22/60] PCI: Get new realloc size for bridge for last try Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 42/60] PCI: Skip required+optional if there is no optional Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 25/60] PCI: Reuse res_to_dev_res() in reassign_resources_sorted() Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 29/60] PCI: Don't add too much optional size for hotplug bridge MMIO Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 35/60] PCI: Simplify res reference using in __assign_resources_sorted() Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 32/60] PCI: Rename pdev_sort_resources() to pdev_assign_resources_prepare() Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 34/60] PCI: Add debug printout during releasing partial assigned resources Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 26/60] PCI: Use correct align for optional only resources during sorting Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 38/60] PCI: Check if resource is allocated before trying to assign one Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 31/60] PCI: Remove duplicated code for resource sorting Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 56/60] PCI: Add debug print out for min_align and alt_size Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 12/60] PCI: Check pref compatible bit for mem64 resource of PCIe device Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 58/60] PCI: Introduce resource_disabled() Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 24/60] PCI: Cleanup res_to_dev_res() printout Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 39/60] PCI: Separate out save_resources()/restore_resources() Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 49/60] PCI: Don't add too much io port for hotplug bridge with old size Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 54/60] resources: Make allocate_resource() return best fit resource Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 46/60] PCI: Fix size calculation with old_size on rescan path Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 48/60] PCI: Move ISA io port align out of calculate_iosize() Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 02/60] alpha/PCI: Only check iomem_is_exclusive() for IORESOURCE_MEM, not IORESOURCE_IO Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 41/60] PCI: Separate required+optional assigning to another function Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 33/60] PCI: Treat ROM resource as optional during realloc Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:30 +0200
  [PATCH v11 28/60] PCI: Optimize bus align/size calculation for optional during sizing Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 04/60] sparc/PCI: Use correct offset for bus address to resource Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 23/60] PCI: Don't release sibling bridge resources during hotplug Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 05/60] sparc/PCI: Reserve legacy mmio after PCI mmio Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 53/60] PCI: Kill macro checking for bus io port sizing Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 03/60] PCI: Add pci_find_bus_resource() Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 11/60] OF/PCI: Add IORESOURCE_MEM_64 for 64-bit resource Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 06/60] sparc/PCI: Add IORESOURCE_MEM_64 for 64-bit resource in OF parsing Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 08/60] PCI: Kill wrong quirk about M7101 Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 14/60] PCI: Add has_mem64 for struct host_bridge Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 30/60] PCI: Reorder resources list for required/optional resources Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 44/60] PCI: Add alt_size ressource allocation support Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
    Re: [PATCH v11 44/60] PCI: Add alt_size ressource allocation support Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-08 03:00 +0200
      Re: [PATCH v11 44/60] PCI: Add alt_size ressource allocation support Yinghai Lu <yinghai@kernel.org> - 2016-04-08 08:00 +0200
      Re: [PATCH v11 44/60] PCI: Add alt_size ressource allocation support Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2016-04-08 08:40 +0200
  [PATCH v11 13/60] PCI: Only treat non-pref mmio64 as pref if all bridges have MEM_64 Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v11 19/60] PCI: Set resource to FIXED for LSI devices Yinghai Lu <yinghai@kernel.org> - 2016-04-08 02:40 +0200
  Re: [PATCH v11 00/60] PCI: Resource allocation cleanup for v4.7 Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-08 03:00 +0200
    Re: [PATCH v11 00/60] PCI: Resource allocation cleanup for v4.7 Yinghai Lu <yinghai@kernel.org> - 2016-04-09 07:40 +0200
  [PATCH v11 50/60] PCI: Unify calculate_size() for io port and MMIO Yinghai Lu <yinghai@kernel.org> - 2016-04-08 03:20 +0200

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