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Sat, 01 Feb 2025 22:57:30 -0800 (PST) MIME-Version: 1.0 References: <20250124164858.756425-1-kevin.brodsky@arm.com> In-Reply-To: <20250124164858.756425-1-kevin.brodsky@arm.com> From: Hyeonggon Yoo <42.hyeyoo@gmail.com> Date: Sun, 2 Feb 2025 15:57:18 +0900 X-Gm-Features: AWEUYZn6OxSb75sYDq_0UftKbKne0UTyN6oHw9v44W4Q1A8hVvd3EAUTqglsJXg Message-ID: Subject: Re: [PATCH v2] mm/slab: simplify SLAB_* flag handling To: Kevin Brodsky Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 6hwn31idszqk3sjpsezjzih6buaddjw3 X-Rspam-User: X-Rspamd-Queue-Id: 42330180002 X-Rspamd-Server: rspam03 X-HE-Tag: 1738479451-342833 X-HE-Meta: U2FsdGVkX18EQFRbXuAR9Yls83kTpA69tVLnr2LzW6+yc8XhDX6LedZDHNtfRXuUnv0X2PjN/nrIxjprB4inm8KTVh5KyPlFSxa7IAXmqqExBpI5o79nxYdimYCQE5o748thntqnRl78j0ShEErNuJa3WWB32rC80LzLeGqWxLADCSNRxr+0BaFRFURZtw0extlTdCRT7EKe7kj7HHnBb8DNt0OxOBaGFwipi39C3Jipr5DxPud+D964djSOn6jiuC0pdoN5SJ6rKnfKhJ65oi20MVB5brcGLTFExT/rqlNFUD+5krzMLpf5ovEbFZZ4QzSYJX3jPVBTtKyU8D7h+a8hFQ5JsdwJ9Tq+c40IXjz3VL4vnf9wQ8ZDO26PoUEHI9hXtZwCarAPAg5RzRDdx6MxL0lE+FHElfW+qqVvk9MVNyz9NZi34lMd0ELccMFmltVsTwmJTJ6g3EydHen7a3d1LKJUayx46K8czBFvq6DcGpSpQ+s0QOK+cuW/Bvl26avV+MGV/zEaDkqPR54A+IiimFdtlDkZSIgJUeW3WGYtLXB4v0dzkJYnYEIwfUw0ctjocRv/1U2CAs5piVzdvOQE/Qa4UiDd/wu7NGpvSJW2drc0Ux08UNoZDK30p3a5zTUrE50m+0yakMSGwouj9oZhBnxYNqcY9sYXYrJ7ts7ictIHY260AKj+kRglSLYDQ/WZYKWuhLoSzigUY6F1fX5282EHJsqG1R4TyPEMoGAE3DQhlEDq7X4tiYwjqiFIpsug+4nUIPlnEPJDy6OP5VoJiET4nk8dEN1NOIAd8IsXLtwH2W6q8aWe5NMUGrhWU8ag6H/PcPAYKRMG1l3ODAjQYEOANsI+HJhvgmEZeSm6fEUtb5/kHR9eNr+LFB/f75hohBx+VCXWy5T60xwVB6rSK4Wnn9CX2InCtAuYRTfUnCg6lH7KxWmPwbNLfLehdQOjiD/UK8XET7NUZtX XUREZRWw IvMkGk/fyQb7Q7NZ4UjuZ6g2gVayBkcSHchlJxeC/DFytMoXXiVDSiesD1sCA212FU2q3jLhunOYPgjV4o8Al4uzbUjXriYjag1xC0anzjWqm+zrE7fMu9CJgFwI2mb91OZIXAgXRgA15I+F+ieBR1/QhCzXUJ60fd1Ko0MSpFGmu9SPAkfof9UPFcwZs0hh3NAVNXDbFGyyzbMra4akBgmwJjhU653/yxaeiNyrZFO4wVRMZLYQffisr4qzz+QlgimmXtVbU4y9m93VMttvscezUhSXOgNhi6wY0rvmAcs+R6/JdiglH31NxepU4tepC7x7UNlVcB1oOAdxHbETRSk59RzrBYemG/RDTyWi0S6drcF9h8/cvN3zp766abJOZaPgh45CJdMuDgvro2sJmFpgz2bqCSt+lMDaP9XcM7PChDsIPNH2qsbMtWbkcdUjwglT0c3xLZT9fyrM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Jan 25, 2025 at 1:49=E2=80=AFAM Kevin Brodsky wrote: > > SLUB is the only remaining allocator. We can therefore get rid of > the logic for allocator-specific flags: > > * Merge SLAB_CACHE_FLAGS into SLAB_CORE_FLAGS. > > * Remove CACHE_CREATE_MASK and instead mask out SLAB_DEBUG_FLAGS if > !CONFIG_SLUB_DEBUG. SLAB_DEBUG_FLAGS is now defined > unconditionally (no impact on existing code, which ignores it if > !CONFIG_SLUB_DEBUG). > > * Define SLAB_FLAGS_PERMITTED in terms of SLAB_CORE_FLAGS and > SLAB_DEBUG_FLAGS (no functional change). > > While at it also remove misleading comments that suggest that > multiple allocators are available. > > Signed-off-by: Kevin Brodsky Hi Kevin, This patch in general looks fine to me. However, there are subtle changes that were not documented by the changelog= . SLUB currently does not _completely_ ignore debug flags even when CONFIG_SLUB_DEBUG=3Dn. For example, calculate_sizes() relocate the free poi= nter regardless of CONFIG_SLUB_DEBUG. I believe completely ignoring debug flags should be acceptable when CONFIG_SLUB_DEBUG=3Dn, but this change should at least be documented in the changelog. Additionally, beyond what this patch currently does, we can remove several CONFIG_SLUB_DEBUG #ifdefs in some functions (e.g., in calculate_sizes()) on top of this patch. How does that sound to you? Best, Hyeonggon