Date: Tue, 30 Aug 2022 11:05:28 -0400 From: Alexander Motin <mav@FreeBSD.org> To: Rick Macklem <rmacklem@uoguelph.ca>, Mateusz Guzik <mjguzik@gmail.com> Cc: "src-committers@FreeBSD.org" <src-committers@FreeBSD.org>, "dev-commits-src-all@FreeBSD.org" <dev-commits-src-all@FreeBSD.org>, "dev-commits-src-main@FreeBSD.org" <dev-commits-src-main@FreeBSD.org> Subject: Re: git: 35b7759c05cb - main - cp: Fix build without VM_AND_BUFFER_CACHE_SYNCHRONIZED. Message-ID: <837f27fc-97b0-6e71-50c0-12b8799e574d@FreeBSD.org> In-Reply-To: <YQXPR01MB41500177CCDFEECFBE95861EDD799@YQXPR01MB4150.CANPRD01.PROD.OUTLOOK.COM> References: <202208301453.27UEroGr037461@gitrepo.freebsd.org> <CAGudoHEphH-4pKGf=ta4AWir2Uj9Mg_tUysU1V5ic6z_XVQG4Q@mail.gmail.com> <YQXPR01MB41500177CCDFEECFBE95861EDD799@YQXPR01MB4150.CANPRD01.PROD.OUTLOOK.COM>
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On 30.08.2022 11:02, Rick Macklem wrote: > Mateusz Guzik <mjguzik@gmail.com> wrote: >> On 8/30/22, Alexander Motin <mav@freebsd.org> wrote: >>> The branch main has been updated by mav: >>> >>> URL: >>> https://cgit.FreeBSD.org/src/commit/?id=35b7759c05cbc65c06d87141da79f0f80af0f458 >>> >>> commit 35b7759c05cbc65c06d87141da79f0f80af0f458 >>> Author: Alexander Motin <mav@FreeBSD.org> >>> AuthorDate: 2022-08-30 14:51:21 +0000 >>> Commit: Alexander Motin <mav@FreeBSD.org> >>> CommitDate: 2022-08-30 14:51:21 +0000 >>> >>> cp: Fix build without VM_AND_BUFFER_CACHE_SYNCHRONIZED. >>> >>> It allows to not use mmap() for small files, which is not helpful >>> in case of ZFS. Should be no functional change. >>> >> >> This should be of no use thanks to copy_file_range > cp does not use copy_file_range(2) for small files, if I recall correctly. Right. I tried to look for motivation, but history of this file goes back to 4.4 Lite. :) I wonder whether copy_file_range(2) for UFS does something clever, like this mmap() to avoid additional memory copy. For ZFS though it cause big problem with buffer cache squeezing ARC to absolute minimum. So if there is agreement to modernize this, I'd completely support it. -- Alexander Motin
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