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AJvYcCXyHx9M8nV/zGxRlqcZ2+qd3J4IC92enxfmHO/t95y/8+IHboeIg/CI2ZkPtYLHK5pmRCjlp67LvA==@kvack.org X-Gm-Message-State: AOJu0YwryTReHAiagV6+ifMWf2gGbBjUd2BrRvynw44Z9m2KehvRimC2 nmcvAO222QXTybrvTr893h2m8A0xbl4TKIB4P1Rg4F1DSP+7IVQFkjUF8R2gldFZ2n5iQnA2bkA wcDJDFEEvnULK7fsYpN4/5dy8Rkg= X-Gm-Gg: ASbGncsBnSpDTh8OWc2fslipczSwSn8FOCJy1pDUCr7SIGLer29vpK1f1o2Aob1ZXIC 2qO9Z/aCXRlVbqJKsXIoAHdxOBB8YK4CJLX+krfbOlr7q1YyQp4uHZEwunftT2PVJ8fDXZXdCNf aJUs3zcIC3IJmc8kI62MUcVrfTrumEf55DE1QhnNSWuw== X-Google-Smtp-Source: AGHT+IFC+7pVYZMM0Are0zBRmUyINtFSZJDWjFDX5AviFPUFAeK9+iklQK+sjlcgAxp8K7xiUFiUqfnT1C3kRVGxKT0= X-Received: by 2002:a05:620a:4053:b0:7c0:a6ce:b5a2 with SMTP id af79cd13be357-7c39c65cc39mr996591985a.40.1740794907459; Fri, 28 Feb 2025 18:08:27 -0800 (PST) MIME-Version: 1.0 References: <20250227001445.1099203-1-nphamcs@gmail.com> In-Reply-To: From: Nhat Pham Date: Fri, 28 Feb 2025 18:08:16 -0800 X-Gm-Features: AQ5f1JqyEYBBBgUCUPdgYFXgP3Vz3mwYcEUDyYrFKZeqBDTW_b5dNl4M3Gn5jrA Message-ID: Subject: Re: [PATCH v2] zswap: do not crash the kernel on decompression failure To: Yosry Ahmed Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, chengming.zhou@linux.dev, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 5AAE31C000A X-Stat-Signature: 89qkw8knqfh7axzqgerq5a4wjdaxzftx X-Rspam-User: X-HE-Tag: 1740794908-819284 X-HE-Meta: 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 YSkD7KkQ uJxbIYc8zMWvC97NKG2Lm+oLGE1OZgJ9mq7wCgBafF9pjF2vO7jNjXgM2BeNx0FDehoBLd+W63r8Iv+T1rnL8WVWfepPNBbgehdjXVGZ8Uc8yzHSGtTsPudErgiiHSkI7pbKIHjDWmpl5oLmqe80gV2fHV4+DiPcK55T+mP8hbRy5bVH8cbGG7JEUxzQ3p8TqAXAoBzQ8MIl7Et3u5lj5XqZgUCR1BDRcaPJHk4iHVJ4KPVvYicTMWFSw5X9zRM3nLhWhyQtlZg3eRD57773Ttk3L9Ij4veFG0d6TGnyfdfKxdWjnxSDmuWia+sGKMPYobypq X-Bogosity: Ham, tests=bogofilter, spamicity=0.004829, 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, Feb 27, 2025 at 1:55=E2=80=AFPM Yosry Ahmed = wrote: > > On Thu, Feb 27, 2025 at 01:46:29PM -0800, Nhat Pham wrote: > > On Wed, Feb 26, 2025 at 5:19=E2=80=AFPM Yosry Ahmed wrote: > > > > > > On Wed, Feb 26, 2025 at 04:14:45PM -0800, Nhat Pham wrote: > > > > Currently, we crash the kernel when a decompression failure occurs = in > > > > zswap (either because of memory corruption, or a bug in the compres= sion > > > > algorithm). This is overkill. We should only SIGBUS the unfortunate > > > > process asking for the zswap entry on zswap load, and skip the corr= upted > > > > entry in zswap writeback. The former is accomplished by returning t= rue > > > > from zswap_load(), indicating that zswap owns the swapped out conte= nt, > > > > but without flagging the folio as up-to-date. The process trying to= swap > > > > in the page will check for the uptodate folio flag and SIGBUS (see > > > > do_swap_page() in mm/memory.c for more details). > > > > > > We should call out the extra xarray walks and their perf impact (if > > > any). > > > > Lemme throw this in a quick and dirty test. I doubt there's any > > impact, but since I'm reworking this patch for a third version anyway > > might as well. > > It's likely everything is cache hot and the impact is minimal, but let's > do the due diligence. > Yeah I ran some kernel building tests for 5 times, and found basically no difference: With the new scheme: real: mean: 125.1s, stdev: 0.12s user: mean: 3265.23s, stdev: 9.62s sys: mean: 2156.41s, stdev: 13.98s The old scheme: real: mean: 125.78s, stdev: 0.45s user: mean: 3287.18s, stdev: 5.95s sys: mean: 2177.08s, stdev: 26.52s Honestly, eyeballing the results, the mean difference is probably smaller than between-run variance. :)