RT tasks are allowed to dip below the min reserve but ALLOC_HARDER is
typically combined with ALLOC_MIN_RESERVE so RT tasks are a little
unusual. While there is some justification for allowing RT tasks access
to memory reserves, there is a strong chance that a RT task that is also
under memory pressure is at risk of missing deadlines anyway. Relax how
much reserves an RT task can access by treating it the same as __GFP_HIGH
allocations.
Note that in a future kernel release that the RT special casing will be
removed. Hard realtime tasks should be locking down resources in advance
and ensuring enough memory is available. Even a soft-realtime task like
audio or video live decoding which cannot jitter should be allocating both
memory and any disk space required up-front before the recording starts
instead of relying on reserves. At best, reserve access will only delay
the problem by a very short interval.
Link: https://lkml.kernel.org/r/20230113111217.14134-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Discard __GFP_ATOMIC", v3.
Neil's patch has been residing in mm-unstable as commit 2fafb4fe8f7a ("mm:
discard __GFP_ATOMIC") for a long time and recently brought up again.
Most recently, I was worried that __GFP_HIGH allocations could use
high-order atomic reserves which is unintentional but there was no
response so lets revisit -- this series reworks how min reserves are used,
protects highorder reserves and then finishes with Neil's patch with very
minor modifications so it fits on top.
There was a review discussion on renaming __GFP_DIRECT_RECLAIM to
__GFP_ALLOW_BLOCKING but I didn't think it was that big an issue and is
orthogonal to the removal of __GFP_ATOMIC.
There were some concerns about how the gfp flags affect the min reserves
but it never reached a solid conclusion so I made my own attempt.
The series tries to iron out some of the details on how reserves are used.
ALLOC_HIGH becomes ALLOC_MIN_RESERVE and ALLOC_HARDER becomes
ALLOC_NON_BLOCK and documents how the reserves are affected. For example,
ALLOC_NON_BLOCK (no direct reclaim) on its own allows 25% of the min
reserve. ALLOC_MIN_RESERVE (__GFP_HIGH) allows 50% and both combined
allows deeper access again. ALLOC_OOM allows access to 75%.
High-order atomic allocations are explicitly handled with the caveat that
no __GFP_ATOMIC flag means that any high-order allocation that specifies
GFP_HIGH and cannot enter direct reclaim will be treated as if it was
GFP_ATOMIC.
This patch (of 6):
__GFP_HIGH aliases to ALLOC_HIGH but the name does not really hint what it
means. As ALLOC_HIGH is internal to the allocator, rename it to
ALLOC_MIN_RESERVE to document that the min reserves can be depleted.
Link: https://lkml.kernel.org/r/20230113111217.14134-1-mgorman@techsingularity.net
Link: https://lkml.kernel.org/r/20230113111217.14134-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by using bit 1. This bit
should be safe to use for our usecase.
Most importantly, we can still distinguish swap PTEs from PAGE_NONE PTEs
(see pte_present()) and don't use one of the two reserved attribute masks
(1101 and 1111). Attribute mask 1100 and 1110 now identify swap PTEs.
While at it, remove SWP_TYPE_BITS (not really helpful as it's not used in
the actual swap macros) and mask the type in __swp_entry().
Link: https://lkml.kernel.org/r/20230113171026.582290-26-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by reusing the SRMMU_DIRTY bit
as that seems to be safe to reuse inside a swap PTE. This avoids having
to steal one bit from the swap offset.
While at it, relocate the swap PTE layout documentation and use the same
style now used for most other archs. Note that the old documentation was
wrong: we use 20 bit for the offset and the reserved bits were 8 instead
of 7 bits in the ascii art.
Link: https://lkml.kernel.org/r/20230113171026.582290-22-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by using bit 6 in the PTE,
reducing the swap type in the !CONFIG_X2TLB case to 5 bits. Generic MM
currently only uses 5 bits for the type (MAX_SWAPFILES_SHIFT), so the
stolen bit is effectively unused.
Interrestingly, the swap type in the !CONFIG_X2TLB case could currently
overlap with the _PAGE_PRESENT bit, because there is a sneaky shift by 1
in __pte_to_swp_entry() and __swp_entry_to_pte(). Bit 0-7 in the
architecture specific swap PTE would get shifted to bit 1-8 in the PTE.
As generic MM uses 5 bits only, this didn't matter so far.
While at it, mask the type in __swp_entry().
Link: https://lkml.kernel.org/r/20230113171026.582290-21-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 32bit and 64bit.
On 64bit, let's use MSB 56 (LSB 7), located right next to the page type.
On 32bit, let's use LSB 2 to avoid stealing one bit from the swap offset.
There seems to be no real reason why these bits cannot be used for swap
PTEs. The important part is that _PAGE_PRESENT and _PAGE_HASHPTE remain
0.
While at it, mask the type in __swp_entry() and remove _PAGE_BIT_SWAP_TYPE
from pte-e500.h: while it was used in 64bit code it was ignored in 32bit
code.
Link: https://lkml.kernel.org/r/20230113171026.582290-19-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We already implemented support for 64bit book3s in commit bff9beaa2e
("powerpc/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE for book3s")
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE also in 32bit by reusing yet
unused LSB 2 / MSB 29. There seems to be no real reason why that bit
cannot be used, and reusing it avoids having to steal one bit from the
swap offset.
While at it, mask the type in __swp_entry().
Link: https://lkml.kernel.org/r/20230113171026.582290-18-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
nios2 disables swap for a good reason: it doesn't even provide sufficient
type bits as required by core MM. However, swap entries are nowadays also
used for other purposes (migration entries, PTE markers, HWPoison, ...),
and accidential use could be problematic.
Let's properly use 5 bits for the swap type and document the layout. Bits
26--31 should get ignored by hardware completely, so they can be used.
Link: https://lkml.kernel.org/r/20230113171026.582290-14-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE.
On 64bit, steal one bit from the type. Generic MM currently only uses 5
bits for the type (MAX_SWAPFILES_SHIFT), so the stolen bit is effectively
unused.
On 32bit we're able to locate unused bits. As the PTE layout for 32 bit
is very confusing, document it a bit better.
While at it, mask the type in __swp_entry()/mk_swap_pte().
Link: https://lkml.kernel.org/r/20230113171026.582290-13-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
type. Generic MM currently only uses 5 bits for the type
(MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.
The shift by 2 when converting between PTE and arch-specific swap entry
makes the swap PTE layout a little bit harder to decipher.
While at it, drop the comment from paulus---copy-and-paste leftover from
powerpc where we actually have _PAGE_HASHPTE---and mask the type in
__swp_entry_to_pte() as well.
Link: https://lkml.kernel.org/r/20230113171026.582290-12-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
type. Generic MM currently only uses 5 bits for the type
(MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.
While at it, make sure for sun3 that the valid bit never gets set by
properly masking it off and mask the type in __swp_entry().
Link: https://lkml.kernel.org/r/20230113171026.582290-11-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
type. Generic MM currently only uses 5 bits for the type
(MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.
While at it, also mask the type in mk_swap_pte().
Note that this bit does not conflict with swap PMDs and could also be used
in swap PMD context later.
Link: https://lkml.kernel.org/r/20230113171026.582290-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
offset. This reduces the maximum swap space per file to 16 GiB (was 32
GiB).
We might actually be able to reuse one of the other software bits
(_PAGE_READ / PAGE_WRITE) instead, because we only have to keep
pte_present(), pte_none() and HW happy. For now, let's keep it simple
because there might be something non-obvious.
Link: https://lkml.kernel.org/r/20230113171026.582290-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Guo Ren <guoren@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
offset. This reduces the maximum swap space per file to 64 GiB (was 128
GiB).
While at it drop the PTE_TYPE_FAULT from __swp_entry_to_pte() which is
defined to be 0 and is rather confusing because we should be dealing with
"Linux PTEs" not "hardware PTEs". Also, properly mask the type in
__swp_entry().
Link: https://lkml.kernel.org/r/20230113171026.582290-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This brings mlock in line with the folio batches declared in mm/swap.c and
makes the code more consistent across the two.
The existing mechanism for identifying which operation each folio in the
batch is undergoing is maintained, i.e. using the lower 2 bits of the
struct folio address (previously struct page address). This should
continue to function correctly as folios remain at least system
word-aligned.
All invocations of mlock() pass either a non-compound page or the head of
a THP-compound page and no tail pages need updating so this functionality
works with struct folios being used internally rather than struct pages.
In this patch the external interface is kept identical to before in order
to maintain separation between patches in the series, using a rather
awkward conversion from struct page to struct folio in relevant functions.
However, this maintenance of the existing interface is intended to be
temporary - the next patch in the series will update the interfaces to
accept folios directly.
Link: https://lkml.kernel.org/r/9f894d54d568773f4ed3cb0eef5f8932f62c95f4.1673526881.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "convert hugepage memory failure functions to folios".
This series contains a 1:1 straightforward page to folio conversion for
memory failure functions which deal with huge pages. I renamed a few
functions to fit with how other folio operating functions are named.
These include:
hugetlb_clear_page_hwpoison -> folio_clear_hugetlb_hwpoison
free_raw_hwp_pages -> folio_free_raw_hwp
__free_raw_hwp_pages -> __folio_free_raw_hwp
hugetlb_set_page_hwpoison -> folio_set_hugetlb_hwpoison
The goal of this series was to reduce users of the hugetlb specific page
flag macros which take in a page so users are protected by the compiler to
make sure they are operating on a head page.
This patch (of 8):
Use a folio throughout the function rather than using a head page. This
also reduces the users of the page version of hugetlb specific page flags.
Link: https://lkml.kernel.org/r/20230112204608.80136-2-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
