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[209.85.208.48]) by smtp.gmail.com with ESMTPSA id l16-20020a170906939000b00930d505a567sm7432649ejx.128.2023.04.05.08.26.36 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Apr 2023 08:26:36 -0700 (PDT) Received: by mail-ed1-f48.google.com with SMTP id y4so142093152edo.2 for ; Wed, 05 Apr 2023 08:26:36 -0700 (PDT) X-Received: by 2002:a17:907:2075:b0:947:72cd:9325 with SMTP id qp21-20020a170907207500b0094772cd9325mr1890350ejb.15.1680708395703; Wed, 05 Apr 2023 08:26:35 -0700 (PDT) MIME-Version: 1.0 References: <20230405022702.753323-1-mcgrof@kernel.org> <20230405022702.753323-6-mcgrof@kernel.org> In-Reply-To: <20230405022702.753323-6-mcgrof@kernel.org> From: Linus Torvalds Date: Wed, 5 Apr 2023 08:26:18 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 5/6] debugfs: add debugfs_create_atomic64_t for atomic64_t To: Luis Chamberlain Cc: david@redhat.com, patches@lists.linux.dev, linux-modules@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, pmladek@suse.com, petr.pavlu@suse.com, prarit@redhat.com, gregkh@linuxfoundation.org, rafael@kernel.org, christophe.leroy@csgroup.eu, tglx@linutronix.de, peterz@infradead.org, song@kernel.org, rppt@kernel.org, dave@stgolabs.net, willy@infradead.org, vbabka@suse.cz, mhocko@suse.com, dave.hansen@linux.intel.com, colin.i.king@gmail.com, jim.cromie@gmail.com, catalin.marinas@arm.com, jbaron@akamai.com, rick.p.edgecombe@intel.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BB3F140017 X-Rspam-User: X-Stat-Signature: 1pa7ipajpx587u5ftc1dbog5y8hn8nhu X-HE-Tag: 1680708399-200881 X-HE-Meta: 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 5/DbzrQb 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 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: On Tue, Apr 4, 2023 at 7:27=E2=80=AFPM Luis Chamberlain = wrote: > > Sometimes you want to add debugfs entries for atomic counters which > can be pretty large using atomic64_t. Add support for these. So I realize why you use atomic64, but I really suspect you'd be better off with just the regular "atomic_long". This is not some debug stat that we care deeply about on 32-bit, and "atomic64" is often really really nasty on 32-bit architectures. For example, on x86, instead of being a single instruction, it ends up being a cmpxchg loop. In fact, even a single atomic read is a cmpxchg (admittedly without the need for looping). And yeah, I realize that we don't have a "atomic_long" debugfs interface either. But I think we could just use atomic_long for the module code (avoiding all the horrors of 64-bit atomics on 32-bit architectures), and then using just 'var->counter' for the value. It's not like the debugfs stuff actually does any truly atomic updates. So something like debugfs_create_ulong(... &val->counter ..); instead of debugfs_create_atomic64(... &val ..); Hmm? I dunno. I just think this is not something that may be worth introducing a new thing for, when it is *so* painful on 32-bit, and doesn't seem worth it. Linus