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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id jc4-20020a17090325c400b001cc52b58df6sm322717plb.215.2023.11.07.14.50.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Nov 2023 14:50:02 -0800 (PST) Date: Tue, 7 Nov 2023 14:50:01 -0800 From: Kees Cook To: Mateusz Guzik Cc: Josh Triplett , Eric Biederman , Alexander Viro , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] fs/exec.c: Add fast path for ENOENT on PATH search before allocating mm Message-ID: <202311071445.53E5D72C@keescook> References: <5c7333ea4bec2fad1b47a8fa2db7c31e4ffc4f14.1663334978.git.josh@joshtriplett.org> <202311071228.27D22C00@keescook> <20231107205151.qkwlw7aarjvkyrqs@f> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 8001518000E X-Rspam-User: X-Stat-Signature: qi6qabckpumsydr9znrkmwjzsq315mun X-Rspamd-Server: rspam03 X-HE-Tag: 1699397404-14542 X-HE-Meta: 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 AOCaL1yv 1XVALfHrka5DW84QsiQpdN8vZZgPnJ453v1wMZWuthIK+dYV6DVddhEWF7uTmpONkVdcBUzif8rZ/2xiRzs1wdhQFwolxh1rMpEYfxNIz3Rzjrqg7KMSo/xlPd3TqW7165UFT5JC5phQU5MLd9miza4BhKOHAhK7UM4psS3gcFQZjPR9PEuD/SR7aEA05uP5bww0PoLGWgex3iW55Selv8KTx2f28X2Ezjjdb3KNwnZ37RkS1kBoQyurDOjC6rkvZQxDyQ4w13Sxeof+446rD72wiE5aHWrZj2qDIr5dyYmC+AgxsK9wf3AFFsEJqInvXpnBScjLmFNYwvWvXF3aqoit/mfo/cPIerhYQ X-Bogosity: Ham, tests=bogofilter, spamicity=0.096931, 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 Tue, Nov 07, 2023 at 10:23:16PM +0100, Mateusz Guzik wrote: > If the patch which dodges second lookup still somehow appears slower a > flamegraph or other profile would be nice. I can volunteer to take a > look at what's going on provided above measurements will be done and > show funkyness. When I looked at this last, it seemed like all the work done in do_filp_open() (my patch, which moved the lookup earlier) was heavier than the duplicate filename_lookup(). What I didn't test was moving the sched_exec() before the mm creation, which Peter confirmed shouldn't be a problem, but I think that might be only a tiny benefit, if at all. If you can do some comparisons, that would be great; it always takes me a fair bit of time to get set up for flame graph generation, etc. :) -Kees -- Kees Cook