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charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3826.200.121\)) Subject: Re: [PATCH v4] mm: add zblock allocator From: Vitaly Wool In-Reply-To: <1ed925bd-897e-44b6-ad20-7d61c8c57aa8@redhat.com> Date: Fri, 18 Apr 2025 12:56:02 +0200 Cc: Johannes Weiner , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Nhat Pham , Shakeel Butt , Igor Belousov Content-Transfer-Encoding: quoted-printable Message-Id: <4CECDD1E-5227-4719-B826-F6AFC77D4D75@konsulko.se> References: <20250412154207.2152667-1-vitaly.wool@konsulko.se> <20250416120912.GC741145@cmpxchg.org> <1ed925bd-897e-44b6-ad20-7d61c8c57aa8@redhat.com> To: David Hildenbrand X-Mailer: Apple Mail (2.3826.200.121) X-Rspamd-Queue-Id: 9C15D1C0009 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: txpp369t6rjnitqk5186h8fc8ngwypjm X-HE-Tag: 1744973777-587825 X-HE-Meta: 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 dIX4FmuN TqmnICIvDqVQILFT6en23ixPJoppeh6Bw+l6heBbmEQgJ/5KKS60ZOK5ZFDnrDrccSmx+ZfQPH0TYuf2igqDNleenQZIOrD3Hzsv+7EOfJ4QP2MhyXETRg4KSlK5Nj917DoNueFeLW+S0XDLfmdlES151srKJH203u/jLZUqF40D18hDiEoN+XR2cVcqpihhTUZ9MawV+uKm1LLFW+owU+v1+2pkeMyLrvAj/ef5Kt8hDpfEIOYVq3ws6F1UsLvBvg8dW6N8tZmDDheFZ4hlRiz23nxOhU1Etb8y7a6mxteqRCHsaDvjD/yIEoqniAPDRQP+40iNURpQFmNI= 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 Apr 18, 2025, at 12:52=E2=80=AFPM, David Hildenbrand = wrote: >=20 > On 16.04.25 14:09, Johannes Weiner wrote: >> On Sat, Apr 12, 2025 at 05:42:07PM +0200, Vitaly Wool wrote: >>> zblock is a special purpose allocator for storing compressed pages. >>> It stores integer number of same size objects per its block. These >>> blocks consist of several physical pages (2**n, i. e. 1/2/4/8). >>>=20 >>> With zblock, it is possible to densely arrange objects of various = sizes >>> resulting in low internal fragmentation. Also this allocator tries = to >>> fill incomplete blocks instead of adding new ones, in many cases >>> providing a compression ratio comparable to zmalloc's. >>>=20 >>> zblock is also in most cases superior to zsmalloc with regard to >>> average performance and worst execution times, thus allowing for = better >>> response time and real-time characteristics of the whole system. >> Is there a reason not to use this allocation scheme in zsmalloc then? >> I'm curious what others think, but I'm still not convinced a second >> allocator makes sense. It's maintenance overhead, a permanent = struggle >> to match feature parity, and it fragments development and testing = base. >> Not long ago several slab allocators were removed for those >> reasons. Likewise, we just deleted zbud and z3fold because they = didn't >> get any attention and bitrotted, but not before years of inflicting >> pain through the zpool interface, users accidentally making very >> suboptimal choices, reporting the same bugs over and over again etc. >> If you discovered a better allocation scheme, that's excellent. But I >> don't see why it warrants forking the entire allocator. >=20 > Just curious, I see a review on v4 happening on something that was = nacked by two people in v2 [1]. >=20 > Do these nack's still apply or were something clarified and they no = longer apply? The reasons for both NAKs are no longer valid (since v3). ~Vitaly >=20 >=20 > [1] = https://lore.kernel.org/linux-mm/CAKEwX=3DMa9phmURz5nyJm0MQrWmXGFLFBPwr8-C= x=3Dzbc473rx9A@mail.gmail.com/ >=20 > --=20 > Cheers, >=20 > David / dhildenb >=20