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AJvYcCVOK410aoPWYuhAhS785qF1c2OvXT3Qj+ybz5xJ1UOtQbTgC1rDr7JJhPvxtIDJHPxw1wdHSEoNWA==@kvack.org X-Gm-Message-State: AOJu0YxupLr+DZiSUPP7J2FUh7bmy3sdKgykTCUHlZpc9/hbbBUaVORK XNIti6p6o8eLdV33EYP+TurhmtX/AqDUXWgoEInHljPE7Sp7+E6UpiNPMnwn/V8i3APAyjmZ9xi njUACIacaRjbgrCY2p9+Mwcs8x+w= X-Gm-Gg: ASbGncuQOhNyfuzqgHwcz3UtdUANv3M4OUE+mmaU17Qb/mOOi4NDcsc6JAHc/8cTd5c /AAUsSN+Kxyix8nr4+h+BE6F4/8Jq/qbVXPSgzgjJhHL5XgkLiGgRfCHLbhgmxZqjd6a39ZDbF9 4Og8OXUJ6fCTI9RiBopqwkr2gIU1s3yhuEbYFffRsdiQ== X-Google-Smtp-Source: AGHT+IEuDq2JeknkTgtYMJm0vZRlgjuGmVz91fqykITW03ONam2Owqld+Uik23to+hzCk0cHIhF++j0NsNzcXsg4WEY= X-Received: by 2002:a05:6000:1889:b0:390:fb37:1bd with SMTP id ffacd0b85a97d-39c1211beabmr19748418f8f.46.1743691523922; Thu, 03 Apr 2025 07:45:23 -0700 (PDT) MIME-Version: 1.0 References: <20250401205245.70838-1-alexei.starovoitov@gmail.com> <78c2d3be-aa8e-4bb7-8883-7f144a06f866@suse.cz> In-Reply-To: <78c2d3be-aa8e-4bb7-8883-7f144a06f866@suse.cz> From: Alexei Starovoitov Date: Thu, 3 Apr 2025 07:45:12 -0700 X-Gm-Features: ATxdqUE7tZW6yPfCiD1FSxwr1kqBj9tR4RS57JdjoIH8NsUBbesBsPHz1WvUpAo Message-ID: Subject: Re: [PATCH v2] locking/local_lock, mm: Replace localtry_ helpers with local_trylock_t type To: Vlastimil Babka Cc: Shakeel Butt , Linus Torvalds , bpf , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Andrew Morton , Peter Zijlstra , Sebastian Sewior , Steven Rostedt , Michal Hocko , linux-mm , LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 1esmewjcorypa36jpdc7grqfaiuupdzy X-Rspam-User: X-Rspamd-Queue-Id: 5E8E540002 X-Rspamd-Server: rspam08 X-HE-Tag: 1743691525-390724 X-HE-Meta: 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 wdRzvP+t uP9MEowTFO70AjMD58AeVIImgI8soRiKL57rrCawXLZyAt0te5aea91CXsLVQr1j6cmOFLgkSToXq5IKcHcAyKnPqy5Q+nekpz3JdvfT4G1BgS7SNtl8dug+SCV84MhkHqJJp5Hb01QBDLcI7WqV1WsiGjXAKeag9KUk34FytEfyF6RAk/7I7FLiPt63NOg5DtKpv48tpUcnVJtxwhjvDGXhLJcQKbVs/jru6BFzqaPZLlIdMpewx7QWOTOGiaQmQfnlVzYpigYDxlcPC0n6xyWKddJJrDDdpXGu4Wrw/jOFa4hCwIqZl7Tc3fJzWguA7UG5BXKnG4u7ssonCWZtrKx8vRIEDw4+iZU1cKZeenA3zHiJniA3ocZeblDjCuFWU+QGc8S7zZlTGMKlwr949Kfle3dyRzqN0DuYqtvA4jbGMiSQfeaKTJup+GwjEUnUpZI++Cv137X+U5Vk= 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 Thu, Apr 3, 2025 at 2:26=E2=80=AFAM Vlastimil Babka wro= te: > > On 4/2/25 23:40, Alexei Starovoitov wrote: > > On Wed, Apr 2, 2025 at 1:56=E2=80=AFPM Shakeel Butt wrote: > >> > >> On Tue, Apr 01, 2025 at 01:52:45PM -0700, Alexei Starovoitov wrote: > >> > From: Alexei Starovoitov > >> > > >> > Partially revert commit 0aaddfb06882 ("locking/local_lock: Introduce= localtry_lock_t"). > >> > Remove localtry_*() helpers, since localtry_lock() name might > >> > be misinterpreted as "try lock". > >> > > >> > Introduce local_trylock[_irqsave]() helpers that only work > >> > with newly introduced local_trylock_t type. > >> > Note that attempt to use local_trylock[_irqsave]() with local_lock_t > >> > will cause compilation failure. > >> > > >> > Usage and behavior in !PREEMPT_RT: > >> > > >> > local_lock_t lock; // sizeof(lock) =3D=3D 0 > >> > local_lock(&lock); // preempt disable > >> > local_lock_irqsave(&lock, ...); // irq save > >> > if (local_trylock_irqsave(&lock, ...)) // compilation error > >> > > >> > local_trylock_t lock; // sizeof(lock) =3D=3D 4 > >> > >> Is there a reason for this 'acquired' to be int? Can it be uint8_t? No > >> need to change anything here but I plan to change it later to compact = as > >> much as possible within one (or two) cachline for memcg stocks. > > > > I don't see any issue. I can make it u8 right away. > > Are you planning to put the lock near other <64bit sized values in memcg > stock? Otherwise it will be padded anyway? > > I hope it won't hurt the performance though, AFAIK at least sub-word atom= ics > are much slower than using a full word. But we use only read/write once f= or > acquired so hopefully it's fine? Sub-words atomics are slow, but these are not atomics. Just plain load/store of u8. Should be fine.