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From: Kent Overstreet To: Eric Biggers Cc: Lorenzo Stoakes , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-bcachefs@vger.kernel.org, Kent Overstreet , Andrew Morton , Uladzislau Rezki , linux-mm@kvack.org Subject: Re: [PATCH 07/32] mm: Bring back vmalloc_exec Message-ID: References: <20230510064849.GC1851@quark.localdomain> <20230513015752.GC3033@quark.localdomain> <20230514184325.GB9528@sol.localdomain> <20230515061346.GB15871@sol.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230515061346.GB15871@sol.localdomain> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 85psgz9yg5ok7rytg35phbpixramqdsu X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6607FA000F X-Rspam-User: X-HE-Tag: 1684131500-356602 X-HE-Meta: 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 dSyiPnkD XxuKuZOkU8SGFeOPQ8IS6OSLXZxkrnbusV3cXt1M/c+OYgr8ArLAk+a91rqr+zks+kB7hensAVDtbm4GdFNeYuTrcPG+5UwdxLQB58kFZvAoRRQHUaupub+e7s8p9odLRptPr2+MXnG+Zjfqortcer/SqFhJxtnihFW+9Er8afuq+VoA/rwi79AgCaxgoCZRrCJCCeo+I0cLJ41YSLnmlxeeVel+osP5+gY5J 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 Sun, May 14, 2023 at 11:13:46PM -0700, Eric Biggers wrote: > On Mon, May 15, 2023 at 01:38:51AM -0400, Kent Overstreet wrote: > > On Sun, May 14, 2023 at 11:43:25AM -0700, Eric Biggers wrote: > > > I think it would also help if the generated assembly had the handling of the > > > fields interleaved. To achieve that, it might be necessary to interleave the C > > > code. > > > > No, that has negligable effect on performance - as expected, for an out > > of order processor. < 1% improvement. > > > > It doesn't look like this approach is going to work here. Sadly. > > I'd be glad to take a look at the code you actually tried. It would be helpful > if you actually provided it, instead of just this "I tried it, I'm giving up > now" sort of thing. https://evilpiepirate.org/git/bcachefs.git/log/?h=bkey_unpack > I was also hoping you'd take the time to split this out into a userspace > micro-benchmark program that we could quickly try different approaches on. I don't need to, because I already have this: https://evilpiepirate.org/git/ktest.git/tree/tests/bcachefs/perf.ktest > BTW, even if people are okay with dynamic code generation (which seems > unlikely?), you'll still need a C version for architectures that you haven't > implemented the dynamic code generation for. Excuse me? There already is a C version, and we've been discussing it. Your approach wasn't any faster than the existing C version.