Re: srat: harsh hot-pluggable memory check?
On Fri, Jan 11, 2013 at 12:13:50PM -0800, Davidlohr Bueso wrote: > On Thu, 2013-01-10 at 21:02 +0100, Andi Kleen wrote: > > > This only mentions that the system supports hot-plugging, and IMHO if the > > > user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered > > > an error. > > > Therefore would it be ok to drop the check? Or am I missing something? > > > > The very strict checks were originally implemented because various early > > BIOS had largely fictional SRATs, and trusting them blindly caused > > boot failures or a lot of wasted memory for unnecessary hotplug zones. > > The wasted memory was mainly a problem with the old memory hotplug > > implementation that pre-allocated memmaps, that's not a problem anymore. > > However there may be still some other failure cases. > > > > Would you be willing to take a patch that drops this check then? Or do > you see any other scenario where it would still be valid? I don't maintain this code. Personally I would be vary to any changes in this area, unless you can very clearly demonstrate that the change cannot break any old system. -Andi -- a...@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: srat: harsh hot-pluggable memory check?
On Thu, 2013-01-10 at 21:02 +0100, Andi Kleen wrote: > > This only mentions that the system supports hot-plugging, and IMHO if the > > user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered > > an error. > > Therefore would it be ok to drop the check? Or am I missing something? > > The very strict checks were originally implemented because various early > BIOS had largely fictional SRATs, and trusting them blindly caused > boot failures or a lot of wasted memory for unnecessary hotplug zones. > The wasted memory was mainly a problem with the old memory hotplug > implementation that pre-allocated memmaps, that's not a problem anymore. > However there may be still some other failure cases. > Would you be willing to take a patch that drops this check then? Or do you see any other scenario where it would still be valid? Thanks, Davidlohr -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: srat: harsh hot-pluggable memory check?
On Thu, 2013-01-10 at 21:02 +0100, Andi Kleen wrote: This only mentions that the system supports hot-plugging, and IMHO if the user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered an error. Therefore would it be ok to drop the check? Or am I missing something? The very strict checks were originally implemented because various early BIOS had largely fictional SRATs, and trusting them blindly caused boot failures or a lot of wasted memory for unnecessary hotplug zones. The wasted memory was mainly a problem with the old memory hotplug implementation that pre-allocated memmaps, that's not a problem anymore. However there may be still some other failure cases. Would you be willing to take a patch that drops this check then? Or do you see any other scenario where it would still be valid? Thanks, Davidlohr -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: srat: harsh hot-pluggable memory check?
On Fri, Jan 11, 2013 at 12:13:50PM -0800, Davidlohr Bueso wrote: On Thu, 2013-01-10 at 21:02 +0100, Andi Kleen wrote: This only mentions that the system supports hot-plugging, and IMHO if the user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered an error. Therefore would it be ok to drop the check? Or am I missing something? The very strict checks were originally implemented because various early BIOS had largely fictional SRATs, and trusting them blindly caused boot failures or a lot of wasted memory for unnecessary hotplug zones. The wasted memory was mainly a problem with the old memory hotplug implementation that pre-allocated memmaps, that's not a problem anymore. However there may be still some other failure cases. Would you be willing to take a patch that drops this check then? Or do you see any other scenario where it would still be valid? I don't maintain this code. Personally I would be vary to any changes in this area, unless you can very clearly demonstrate that the change cannot break any old system. -Andi -- a...@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: srat: harsh hot-pluggable memory check?
> This only mentions that the system supports hot-plugging, and IMHO if the > user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered an > error. > Therefore would it be ok to drop the check? Or am I missing something? The very strict checks were originally implemented because various early BIOS had largely fictional SRATs, and trusting them blindly caused boot failures or a lot of wasted memory for unnecessary hotplug zones. The wasted memory was mainly a problem with the old memory hotplug implementation that pre-allocated memmaps, that's not a problem anymore. However there may be still some other failure cases. -Andi -- a...@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
srat: harsh hot-pluggable memory check?
When parsing the memory affinity mappings in arch/x86/mm/srat.c: acpi_numa_memory_affinity_init() I'm wondering if the hot-pluggable check is too harsh, as we consider an error if the hot-pluggable bit is set and CONFIG_MEMORY_HOTPLUG is not. Based on the ACPI specs (v5): "If the Enabled bit is set and the Hot Pluggable bit is also set. The system hardware supports hot-add and hot-remove of this memory region." This only mentions that the system supports hot-plugging, and IMHO if the user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered an error. Therefore would it be ok to drop the check? Or am I missing something? Thanks, Davidlohr -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
srat: harsh hot-pluggable memory check?
When parsing the memory affinity mappings in arch/x86/mm/srat.c: acpi_numa_memory_affinity_init() I'm wondering if the hot-pluggable check is too harsh, as we consider an error if the hot-pluggable bit is set and CONFIG_MEMORY_HOTPLUG is not. Based on the ACPI specs (v5): If the Enabled bit is set and the Hot Pluggable bit is also set. The system hardware supports hot-add and hot-remove of this memory region. This only mentions that the system supports hot-plugging, and IMHO if the user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered an error. Therefore would it be ok to drop the check? Or am I missing something? Thanks, Davidlohr -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: srat: harsh hot-pluggable memory check?
This only mentions that the system supports hot-plugging, and IMHO if the user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered an error. Therefore would it be ok to drop the check? Or am I missing something? The very strict checks were originally implemented because various early BIOS had largely fictional SRATs, and trusting them blindly caused boot failures or a lot of wasted memory for unnecessary hotplug zones. The wasted memory was mainly a problem with the old memory hotplug implementation that pre-allocated memmaps, that's not a problem anymore. However there may be still some other failure cases. -Andi -- a...@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
