Re: [PATCH v12 9/9] kdump: update Documentation about crashkernel
On Tue, Oct 06, 2020 at 10:10:54AM +0800, chenzhou wrote: > On 2020/10/6 1:19, Catalin Marinas wrote: > > On Mon, Sep 07, 2020 at 09:47:45PM +0800, Chen Zhou wrote: > >> diff --git a/Documentation/admin-guide/kdump/kdump.rst > >> b/Documentation/admin-guide/kdump/kdump.rst > >> index 2da65fef2a1c..549611abc581 100644 > >> --- a/Documentation/admin-guide/kdump/kdump.rst > >> +++ b/Documentation/admin-guide/kdump/kdump.rst > > [...] > >> @@ -316,8 +325,18 @@ Boot into System Kernel > >> kernel will automatically locate the crash kernel image within the > >> first 512MB of RAM if X is not given. > >> > >> - On arm64, use "crashkernel=Y[@X]". Note that the start address of > >> - the kernel, X if explicitly specified, must be aligned to 2MiB > >> (0x20). > >> + On arm64, use "crashkernel=X" to try low allocation in DMA zone, and > >> + fall back to high allocation if it fails. And go for high allocation > >> + directly if the required size is too large. > >> + We can also use "crashkernel=X,high" to select a high region above > >> + DMA zone, which also tries to allocate at least 256M low memory in > >> + DMA zone automatically. > >> + "crashkernel=Y,low" can be used to allocate specified size low memory > >> + in DMA zone. > >> + For non-RPi4 platforms, change DMA zone memtioned above to DMA32 zone. > > I don't think we should mention non-RPi4 explicitly here. I don't even > > understand what the suggestion is since the only way is to disable > > ZONE_DMA in the kernel config. I'd just stick to ZONE_DMA description > > here. > How about like this: > If the kernel config ZONE_DMA is disabled, just try low allocation in DMA32 > zone > and high allocation above DMA32 zone. Something like: "allocate 256M low memory in the DMA zone automatically (or the DMA32 zone if CONFIG_ZONE_DMA is disabled)". I'd keep it short. -- Catalin
Re: [PATCH v12 9/9] kdump: update Documentation about crashkernel
Hi Catalin, On 2020/10/6 1:19, Catalin Marinas wrote: > On Mon, Sep 07, 2020 at 09:47:45PM +0800, Chen Zhou wrote: >> diff --git a/Documentation/admin-guide/kdump/kdump.rst >> b/Documentation/admin-guide/kdump/kdump.rst >> index 2da65fef2a1c..549611abc581 100644 >> --- a/Documentation/admin-guide/kdump/kdump.rst >> +++ b/Documentation/admin-guide/kdump/kdump.rst > [...] >> @@ -316,8 +325,18 @@ Boot into System Kernel >> kernel will automatically locate the crash kernel image within the >> first 512MB of RAM if X is not given. >> >> - On arm64, use "crashkernel=Y[@X]". Note that the start address of >> - the kernel, X if explicitly specified, must be aligned to 2MiB >> (0x20). >> + On arm64, use "crashkernel=X" to try low allocation in DMA zone, and >> + fall back to high allocation if it fails. And go for high allocation >> + directly if the required size is too large. >> + We can also use "crashkernel=X,high" to select a high region above >> + DMA zone, which also tries to allocate at least 256M low memory in >> + DMA zone automatically. >> + "crashkernel=Y,low" can be used to allocate specified size low memory >> + in DMA zone. >> + For non-RPi4 platforms, change DMA zone memtioned above to DMA32 zone. > I don't think we should mention non-RPi4 explicitly here. I don't even > understand what the suggestion is since the only way is to disable > ZONE_DMA in the kernel config. I'd just stick to ZONE_DMA description > here. How about like this: If the kernel config ZONE_DMA is disabled, just try low allocation in DMA32 zone and high allocation above DMA32 zone. Thanks, Chen Zhou > >> + Use "crashkernel=Y@X" if you really have to reserve memory from >> + specified start address X. Note that the start address of the kernel, >> + X if explicitly specified, must be aligned to 2MiB (0x20). >> >> Load the Dump-capture Kernel >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt >> b/Documentation/admin-guide/kernel-parameters.txt >> index a1068742a6df..f7df572d8f64 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -727,6 +727,10 @@ >> [KNL, X86-64] Select a region under 4G first, and >> fall back to reserve region above 4G when '@offset' >> hasn't been specified. >> +[KNL, arm64] Try low allocation in DMA zone, fall back >> +to high allocation if it fails when '@offset' hasn't >> been >> +specified. For non-RPi4 platforms, change DMA zone to >> +DMA32 zone. > Same here, unclear what "change DMA zone to DMA32 zone" means. > >> See Documentation/admin-guide/kdump/kdump.rst for >> further details. >> >> crashkernel=range1:size1[,range2:size2,...][@offset] >> @@ -743,6 +747,8 @@ >> Otherwise memory region will be allocated below 4G, if >> available. >> It will be ignored if crashkernel=X is specified. >> +[KNL, arm64] range in high memory. >> +Allow kernel to allocate physical memory region from >> top. >> crashkernel=size[KMG],low >> [KNL, X86-64] range under 4G. When crashkernel=X,high >> is passed, kernel could allocate physical memory region >> @@ -751,13 +757,16 @@ >> requires at least 64M+32K low memory, also enough extra >> low memory is needed to make sure DMA buffers for 32-bit >> devices won't run out. Kernel would try to allocate at >> -at least 256M below 4G automatically. >> +least 256M below 4G automatically. >> This one let user to specify own low range under 4G >> for second kernel instead. >> 0: to disable low allocation. >> It will be ignored when crashkernel=X,high is not used >> or memory reserved is below 4G. >> - >> +[KNL, arm64] range in low memory. >> +This one let user to specify a low range in DMA zone for >> +crash dump kernel. For non-RPi4 platforms, change DMA >> zone >> +to DMA32 zone. > And again here. >
Re: [PATCH v12 9/9] kdump: update Documentation about crashkernel
On Mon, Sep 07, 2020 at 09:47:45PM +0800, Chen Zhou wrote: > diff --git a/Documentation/admin-guide/kdump/kdump.rst > b/Documentation/admin-guide/kdump/kdump.rst > index 2da65fef2a1c..549611abc581 100644 > --- a/Documentation/admin-guide/kdump/kdump.rst > +++ b/Documentation/admin-guide/kdump/kdump.rst [...] > @@ -316,8 +325,18 @@ Boot into System Kernel > kernel will automatically locate the crash kernel image within the > first 512MB of RAM if X is not given. > > - On arm64, use "crashkernel=Y[@X]". Note that the start address of > - the kernel, X if explicitly specified, must be aligned to 2MiB (0x20). > + On arm64, use "crashkernel=X" to try low allocation in DMA zone, and > + fall back to high allocation if it fails. And go for high allocation > + directly if the required size is too large. > + We can also use "crashkernel=X,high" to select a high region above > + DMA zone, which also tries to allocate at least 256M low memory in > + DMA zone automatically. > + "crashkernel=Y,low" can be used to allocate specified size low memory > + in DMA zone. > + For non-RPi4 platforms, change DMA zone memtioned above to DMA32 zone. I don't think we should mention non-RPi4 explicitly here. I don't even understand what the suggestion is since the only way is to disable ZONE_DMA in the kernel config. I'd just stick to ZONE_DMA description here. > + Use "crashkernel=Y@X" if you really have to reserve memory from > + specified start address X. Note that the start address of the kernel, > + X if explicitly specified, must be aligned to 2MiB (0x20). > > Load the Dump-capture Kernel > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > b/Documentation/admin-guide/kernel-parameters.txt > index a1068742a6df..f7df572d8f64 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -727,6 +727,10 @@ > [KNL, X86-64] Select a region under 4G first, and > fall back to reserve region above 4G when '@offset' > hasn't been specified. > + [KNL, arm64] Try low allocation in DMA zone, fall back > + to high allocation if it fails when '@offset' hasn't > been > + specified. For non-RPi4 platforms, change DMA zone to > + DMA32 zone. Same here, unclear what "change DMA zone to DMA32 zone" means. > See Documentation/admin-guide/kdump/kdump.rst for > further details. > > crashkernel=range1:size1[,range2:size2,...][@offset] > @@ -743,6 +747,8 @@ > Otherwise memory region will be allocated below 4G, if > available. > It will be ignored if crashkernel=X is specified. > + [KNL, arm64] range in high memory. > + Allow kernel to allocate physical memory region from > top. > crashkernel=size[KMG],low > [KNL, X86-64] range under 4G. When crashkernel=X,high > is passed, kernel could allocate physical memory region > @@ -751,13 +757,16 @@ > requires at least 64M+32K low memory, also enough extra > low memory is needed to make sure DMA buffers for 32-bit > devices won't run out. Kernel would try to allocate at > - at least 256M below 4G automatically. > + least 256M below 4G automatically. > This one let user to specify own low range under 4G > for second kernel instead. > 0: to disable low allocation. > It will be ignored when crashkernel=X,high is not used > or memory reserved is below 4G. > - > + [KNL, arm64] range in low memory. > + This one let user to specify a low range in DMA zone for > + crash dump kernel. For non-RPi4 platforms, change DMA > zone > + to DMA32 zone. And again here. -- Catalin
[PATCH v12 9/9] kdump: update Documentation about crashkernel
For arm64, the behavior of crashkernel=X has been changed, which tries low allocation in DMA zone, and fall back to high allocation if it fails. We can also use "crashkernel=X,high" to select a high region above DMA zone, which also tries to allocate at least 256M low memory in DMA zone automatically. "crashkernel=Y,low" can be used to allocate specified size low memory in DMA zone. For non-RPi4 platforms, change DMA zone memtioned above to DMA32 zone. For x86 and arm64, we introduce threshold for the required memory. if required size X is too large and leads to very little free low memory after low allocation, the system may not work well. So add a threshold and go for high allocation directly if the required size is too large. The threshold is set as the half of low memory. So update the Documentation. Signed-off-by: Chen Zhou --- Documentation/admin-guide/kdump/kdump.rst | 25 --- .../admin-guide/kernel-parameters.txt | 13 -- 2 files changed, 33 insertions(+), 5 deletions(-) diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst index 2da65fef2a1c..549611abc581 100644 --- a/Documentation/admin-guide/kdump/kdump.rst +++ b/Documentation/admin-guide/kdump/kdump.rst @@ -299,7 +299,16 @@ Boot into System Kernel "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory starting at physical address 0x0100 (16MB) for the dump-capture kernel. - On x86 and x86_64, use "crashkernel=64M@16M". + On x86 use "crashkernel=64M@16M". + + On x86_64, use "crashkernel=X" to select a region under 4G first, and + fall back to reserve region above 4G. And go for high allocation + directly if the required size is too large. + We can also use "crashkernel=X,high" to select a region above 4G, which + also tries to allocate at least 256M below 4G automatically and + "crashkernel=Y,low" can be used to allocate specified size low memory. + Use "crashkernel=Y@X" if you really have to reserve memory from specified + start address X. On ppc64, use "crashkernel=128M@32M". @@ -316,8 +325,18 @@ Boot into System Kernel kernel will automatically locate the crash kernel image within the first 512MB of RAM if X is not given. - On arm64, use "crashkernel=Y[@X]". Note that the start address of - the kernel, X if explicitly specified, must be aligned to 2MiB (0x20). + On arm64, use "crashkernel=X" to try low allocation in DMA zone, and + fall back to high allocation if it fails. And go for high allocation + directly if the required size is too large. + We can also use "crashkernel=X,high" to select a high region above + DMA zone, which also tries to allocate at least 256M low memory in + DMA zone automatically. + "crashkernel=Y,low" can be used to allocate specified size low memory + in DMA zone. + For non-RPi4 platforms, change DMA zone memtioned above to DMA32 zone. + Use "crashkernel=Y@X" if you really have to reserve memory from + specified start address X. Note that the start address of the kernel, + X if explicitly specified, must be aligned to 2MiB (0x20). Load the Dump-capture Kernel diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a1068742a6df..f7df572d8f64 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -727,6 +727,10 @@ [KNL, X86-64] Select a region under 4G first, and fall back to reserve region above 4G when '@offset' hasn't been specified. + [KNL, arm64] Try low allocation in DMA zone, fall back + to high allocation if it fails when '@offset' hasn't been + specified. For non-RPi4 platforms, change DMA zone to + DMA32 zone. See Documentation/admin-guide/kdump/kdump.rst for further details. crashkernel=range1:size1[,range2:size2,...][@offset] @@ -743,6 +747,8 @@ Otherwise memory region will be allocated below 4G, if available. It will be ignored if crashkernel=X is specified. + [KNL, arm64] range in high memory. + Allow kernel to allocate physical memory region from top. crashkernel=size[KMG],low [KNL, X86-64] range under 4G. When crashkernel=X,high is passed, kernel could allocate physical memory region @@ -751,13 +757,16 @@ requires at least 64M+32K low memory, also enough extra low memory is needed to make sure DMA buffers for 32-bit devices won't run out. Kernel would try to allocate at - at least 256M below 4G
